Okay, I see you had replied while I was typing. Sorry, I thought you were talking about 3C difference side to side. My bad.

I’d still suggest clamping off the heater return line to be sure. Maybe my “ambient” test is not as conclusive as I thought. With the line clamped and thus no possibility of any heat entering the ducts, see what the AC side of the HVAC system can really do.

I think I’d want to do that before condemning the ACCM. On a 2003+ car, the typical ACCM failure (burnt traces) causes full heat output, and you don’t seem to be having that problem.

 

No the current to the DCCV is under 2A and with the AC Clutch it rises to 5.4A, Across the fuse it is 18mV and 48mV.
I don't think that any tracks are burnt, everything is normal. I am not very keen on putting mole grips on the pipe and I certainly would not drive
it like that but I will try it.and post the results.The common/return Pipe is the one that sticks up at a right angle correct?
Tomorrow I will get the Low pressure measurement to have an idea about the compressor state, At idle the AC is poor. I made a tool to clean the
Condenser with a water jet from inside, hopefully it will work better now.
The difference side to side is with. (LO AC On) No Difference side to side with LO AC Off.
Thanks and good night.
Mike

 

I've got to admit I'm thoroughly confused.

The duct temp you recorded with no AC and (theoretically) no heat, at 3C above ambient, is probably okay. Ideally it should be a little closer, but it doesn't seem excessive. Yet when you turn on the AC, you get one side reading higher. This is what has me stumped.

All cabin air passes through the evaporator, whether the AC is on or off. If the AC is on, the evaporator should cool both sides equally. From there, all cabin air then passes through the heater core, whether the coolant inside is hot or cold. In this manner, the evaporator and heater core are similar, with all air passing through both whether they are working on not. The heater core, however, is split side to side, basically two separate units in a common housing.. AFAIK, the only way to split the temperature is to add heat to one side. The evaporator can't do it, as it feeds both sides equally.

With the system in manual (LO selected), you should not be able to command one side warmer than the other. The two duct temperature sensors are inhibited. Even if one was bad, it shouldn't matter in LO. See why I'm so confused? I just don't get why one side is repeatably warmer than the other in manual LO. It seems hot coolant is somehow making it past the DCCV. I keep thinking the ambient air test is flawed in some unforeseen manner, but it wasn't noticeable until now.

That's why I recommend pinching off the heater return line. You've said you are hesitant to do this, and so am i, but the pros do it all the time with no ill effect. If you physically block the coolant flow, we can safely confirm or rule out this possibility. The heater return line is the larger of the three. Please see post #2 in the troubleshooting guide for a good illustration.

Back to the guide, have you tried the other test of the DCCV, with an infrared thermometer on the lines? This test is very accurate, in my overrated opinion, but you have to begin with a cold engine.

Another possibility is this duct temperature split isn't a big deal. The total amount of extra heat you're possibly getting doesn't seem to be enough to cause such poor cooling performance. Since we don't seem to be making any progress, we could put that on the back burner and turn our attention elsewhere. In particular, have you checked the compressor clutch for slippage? Have you swapped the control relay? All very easy to do, details in the troubleshooting guide, posts #4 or #5, IIRC.

 

I have checked the compressor today LP side 39C at Idle, with a few extra revs it drops to 36C, I swapped the compressor clutch relay with the fog light one with no change.
Yesterday cleaning the Condenser radiator blowing water through it from behind, I got soaked but it is cooling better today especially at idle.
Tomorrow morning I will clamp the Hose. My DCCV has 5 hoses, 2 small going to the heating system and 3 large. The lower 2 large ones appear to go straight through, the Upper one at a right angle to the body would seem to be the one to clamp. The guy that did the Low pressure test was the one that did the gas vac and refill.

 

I’m not familiar with this test. Are you measuring the inlet line at the compressor with an infrared thermometer? If so, what is a normal value? I’m not sure if your measurements are good or bad, but that seems high.

Have you done the paint mark test for clutch slippage?

 

Sorry got my units mixed up, that was 39 PSI and 36PSI. An hour or so ago I checked the "OLD" DCCV, Applying 13V sound is soft, Left side almost closes and right side remains open, confirming how tube felt hot on my fingers. Current about 700mA to each half, read off PSU meter.
Maybe the A/CCM was constantly trying to close the hot half. Having said that the AC did appear to sort of work in the spring.
I only got this car in Nov 2019 so I know nothing about how it worked before and had no contact with the previous owner unfortunately.
Paint mark test has not been done but it seemed quite fresh on the Left side this morning (Right still less cold) after the condenser cleaning, I didn't measure it
but my wife didn't make her usual comments about the AC. Must be getting better !!!

 

Hmm, 36 PSI would indicate good performance from the compressor. On my car, I had 39 with nice frosty air.

Now I'm wondering if your evaporator could be freezing up, causing excessive ice to accumulate on the face. Maybe your evaporator is getting just a smidge too cold.

Two easy ways to check. I'd suggest doing both. You will need a thermometer in the vent, so make sure that is handy:

1) In the early morning, while everything is still cool, start the car and select manual LO. Start driving as soon as possible, for good airflow through the condenser. The idea is you want optimal conditions right away for maximum cooling. This won't work if the car is hot from the sun, etc. Under these optimal conditions, watch the duct temperature like a hawk for the first few minutes. If the temperature drops below 38F during these first few minutes, you've probably got a bad evaporator temperature sensor letting things get too cold. Might sound good, but it's not, as ice will build up and actually reduce cooling.

2) After a long drive, at least half an hour or so, park on a cool hard surface. Watch how much water drips from the evaporator drain after shutdown. You don't have to watch the entire time. Just note the size of the puddle after 30 minutes. The idea is you want a cool hard surface for the water to collect and not evaporate quickly. A garage with a cement floor is ideal. A gravel parking lot in the sun is bad. A small puddle is fine, maybe 6 inches across. You will always get a little ice, but too much is a problem. Actually, you should see a light steady drop as the AC is running, too. No dripping means all moisture is turning to ice, not running off as it should.

Re: Amperage draw of the DCCV - Be careful because this can be misleading. If too much or too little, yes that means a bad unit. But you can have a jammed valve that can't move. However, that coil of fine wire (inside the solenoid) will draw the same basic amount of current whether the valve actually responds or not.

I don't know for sure, but don't believe there is any feedback to tell if the valve responded to a command. You'd think the duct temperature sensor for each side could monitor DCCV response, but I couldn't find anything saying this is the case. Those sensors do let the ACCM know if more heating or cooling is required, but that's about it.

 

No Karl, I got a slightly wavery 39PSI at idle with 25C ambient, this went down putting some revs on it to 36PSI. I will get the Vent Temp tomorrow AM when I start it up before it starts to go up.
Here minimum temp in the morning is 25C and there is 330 days a year sun!! I got the evaporator temperature setting from the OBD Icsoft i930 at 38C. When I come back I will block the Tube on the DCCV. and see if both sides are the same.
The Current readings were from the defective DCCV, If I remember correctly the new one is about 900mA per side.
More tomorrow, Later today I should say here.
Mike

 

38C or 38F? Is that what the ACCM thinks the temperature is at the evaporator? 38F sounds right, so that's why I'm asking. Or is 38C your ambient temperature?

More thinking out loud, but let's say the evaporator temperature sensor is slightly inaccurate. The poor computer thinks the actual value is 38F, which I think is the target temperature at the evaporator. If colder than that, cooling is reduced to get the temp back up around 38F, just enough of a margin above freezing to prevent ice accumulation. But what if that sensor was actually reading high by a few degrees? Maybe the real temperature at the evaporator is 32F, and all sorts of ice is accumulating. Meanwhile, the ACCM is still happy because it thinks the target of 38F has been achieved.

I think the two tests I just suggested should help determine if the evaporator is being kept just warm enough to prevent icing. Remember, you should also see water dripping while the AC is running. That's another big indicator that moisture is being properly kept from freezing.

 

Just went for a 5 minute drive, Ambient 77F, 55% humidity, because of traffic limited to 30 MPH or less, All Measurements on Left Vent temperature showed 50F after about 2 mins, One little bit of road then got up to between 40 and 45 MPH temp dropped to 47F after that back to 50F and then with stops and engine temperature rising went up to 55F. OBD2 Evaporator air off temperature says 64F whatever that means. Relative Humidity according to OBD2 38%. Temp at IDLE 55F. No sign of any water on the ground maybe too dry or just not enough.
Will do the clamp test later.
Cheers
Have a nice day
Mike

 

Clamped the hose as best I could With a G clamp, probably not 100% but almost, afraid of damaging the hose. The Vent readings were within less than 1 degree of each other, difference almost not discernable. Removed the clamp and we went back to our 9F difference Right side 9F higher. Tried putting a DVM across the 2 outputs of the A/CCM and got a 0.1mV increase or decrease depending on polarity ( to eliminate spurious effects, so the direction of the impulse was always the same, Positive,ie Valve open) and again after a couple of minutes. Set higher range on DVM and selected 65F on LHS and 80F on RHS and the tester showed for a second or so 13.6V and the next time a lower voltage and so on (Shown voltage was lower because control pulse/Valve open was shorter). Back to cooling on RHS. Put a 12V LED in place of the meter and set the RHS again to 80F, The LED Flashed for about a second then after a minute or so another shorter flash and so it continued with the flashes getting shorter until they were not seen any more, I guess it reached 80F. The A/CCM modulates the open time of the valve. It needs a storage scope with a 1 shot sync to catch/see it, as the temperature gets closer to the required value the switching pulses get shorter and more spaced out in time.
The condensation appears OK too.
I think I need a new A/CCM or can it be reset?
There are no cables attached to my LHS Temperature sensor, see picture !!

 

Okay, time for me to wander out onto the abandoned railroad track, sit down with a book, and read between the lines. When you mentioned the difference in the vent readings, what mode were you in when you mentioned the side to side difference? Was the AC on? Was LO or auto selected? Or AC off, LO selected, and your reading was vent compared to ambient? The 9F difference is a very important clue, but I don't understand the conditions you were measuring.

The side to side split you did mention continues to point to a problem with the DCCV or control circuit. That's why I keep harping to stick to LO when checking the AC performance. This helps rule out most of the inputs from the automatic control system. One crisis at a time. Most likely you have two (or more) faults active. Insufficient cooling in LO is the primary fault. We can come back later to any faults in auto mode. But stick to LO for now so we don't end up in the weeds.

I think you have this backwards. The individual valves in the DCCV are spring-loaded open. Power = valve closed. IF (big if) the DCCV itself is behaving correctly, and both sides have been commanded closed (no heat), you should see full voltage across each solenoid (100% pulse width). The only time you should see lower voltage is when heat is commanded and the pulse width is reduced to let the valves relax to the open position.

Please define "OK". Does this mean you had a normal amount? None? In your previous message, you said you didn't see any dripping, so I'm confused.

I highly doubt your ACCM is at fault. I'm pretty sure we're looking at a combination of minor input faults, and maybe a DCCV bad from stock.

Kinda hard to believe, those wires may be above the sensor where you can't see them. Who knows, maybe a previous owner was in there. However, if we stick to troubleshooting LO mode for now, you could unplug those two duct temp sensors and never even know it.

If still unconvinced, remove the ACCM and measure the resistance of the three sensors. If you show an open circuit for the left duct temp sensor, then yep, that's a problem, but only in automatic mode. Remember, the two duct temp sensors are bypassed in LO mode. The third sensor (evaporator temp) is the important one and is active in all cooling modes. Fortunately, all three are the same part number. Let the car sit for a couple of hours so all of the ducts can equalize in temperature. The three sensors should show very similar resistance values. This isn't a conclusive test that all three are good, but if you see a big split then you know at least one is bad. I'm still leaning towards a bad evap temp sensor letting ice accumulate.

 

For comparison, I tested my '02 this morning. Engine cold from sitting overnight. Ambient 64F, 75% humidity. Still dark, so no solar load. The fires from the Antifa riots had mostly died down, so minimal effect there. Stage Fright by The Band playing on the stereo. This was the studio version, still a great song, but not quite as powerful as the live version from The Last Waltz.

Manual LO selected. Within 2 minutes, still parked, engine at idle, the left vent showed 40F. If I were smuggling penguins, they'd chirp out in their special language that they were cold.

I observed my car this morning. After a 20 minute freeway drive, followed by 5 mins at lower speed, I shut off the engine (I should clarify I was parked by now). I had carefully checked my parking spot before pulling in, and it was clean. I waited two minutes. I passed the time finishing my coffee (black in a dirty cup) and listening to the end of Dream in Blue by Los Lobos. Under the condensate drain, I saw a small puddle, maybe 1.5 inches in diameter at the most. In parts of the world that use the metric system, that's 1.5 inches. Since my AC is nice and frosty (see previous comments about complaints from penguins), I'd say that is a normal amount.

​​​​​​​Thanks, but I had other plans.
​​​​​​​

 

Quote:
Originally Posted by mrmike View Post
(Shown voltage was lower because control pulse/Valve open was shorter).
I think you have this backwards. The individual valves in the DCCV are spring-loaded open. Power = valve closed. IF (big if) the DCCV itself is behaving correctly, and both sides have been commanded closed (no heat), you should see full voltage across each solenoid (100% pulse width). The only time you should see lower voltage is when heat is commanded and the pulse width is reduced to let the valves relax to the open position.
ALWAYS in LO and AC on.
I am looking at pins 9 and 10 on Connector FC4, When these are low the Valves are closed because it has about 13.5V across it (Pins 2 and 3 0n the DCCV go to pins 9 and 10 on FC4 which in turn go to FC40 27-6 and 27-5 on the A/CCM. Better than my clamping the hose was holding the FC4 9 and 10 pins to chassis This closed the valves and the temperature from the vents was EQUAL As I had originally said. The problem is in LO or Manual, Removing the chassis connection on FC4 and 9. The A/CCM is letting the right side go high ie Valve open for short periods resulting in a 9F increase on the right vent. Manually setting both sides to 63F the right side is always much warmer.
Quoting from above "you should see full voltage across each solenoid (100% pulse width).(NO HOT WATER) The only time you should see lower voltage ( Only 2 states 13V or 0V,) is when heat is commanded and the pulse width (13V 0V across solenoid.) is reduced to let the valves relax to the open position ( for a short squirt of hot water) The pulse width and Pulse Repetition rate control the temperature on each side.
Connecting pins 2 and 3 on DCCV To Chassis results in equal temperatures on both vents R&L

 

Putting on my orthopedic thinking cap:

I wonder if you have a bad/broken connection between FC4 pin 9 and the ACCM. When you apply the ground directly at FC4 pin 9, the right side of the DCCV responds properly. When the ACCM tries to apply this same ground, nothing happens. I'd ring out the wire to be sure. Looking at the wiring diagram, it looks like you could even apply a ground directly at the ACCM connector FC40 27-06. Power to the center pin of the DCCV comes from front fuse F32, so you'll still have power at the DCCV even with the ACCM disconnected. If the valve closes properly with a ground at the ACCM connector, that should be a good test of the connecting wiring.

The other possibility is a burnt trace inside the ACCM. Might be worth opening the module for a visual inspection:

https://jaguarclimatecontrol.com/new...-way-to-do-it/

After you open the module, that same page has a link showing the damage you might see.

Now I think when a trace burns up inside the ACCM, I could have sworn you'd get a LOT of heat, but who knows.

While you've got the ACCM removed, I'd suggest comparing the three temperature sensors, details in an earlier message.

 

What I am thinking is maybe someone had a go at repairing the A/CCM and maybe caused a short somewhere else in it at the same time.
I will definitely need to open it and have a look. Of course it could just be something with the processor!
The connections to the A/CCM must be OK because it maintains control even though it is wrong and I have seen the pulses opening the RH valve.
I need to check the sensors too.
Cheers
Mike

 

I read this message again. When you connected the LED to observe the PWM action, was the DCCV still connected? In other words, was the ACCM driving the DCCV and LED together at the time? Or just the LED?

The reason I ask is very important. The amp draw is minuscule to drive just an LED. If that's how you did it, the circuit is basically unloaded while under test. You could have a bad spot in the wiring, such as a damaged crimp at a connector, and only a few strands are intact. This would still test perfectly in an unloaded condition, whether you used an LED or a multimeter, because the amp draw is so tiny. But connect the DCCV and the amperage requirement jumps up. The damaged wiring can not deliver this increased flow of electrons. The circuit fails under load, but tests perfectly unloaded.

I had the good fortune to have an excellent electronics instructor many years ago. He taught me to always be suspicious of a good test in an unloaded circuit. Just because a voltage or resistance check passed when unloaded, that does not mean the circuit is good. Like everybody else, I'll typically first check a circuit unloaded looking for obvious faults, such as no voltage meaning a total break somewhere. But I am very thankful for what I was taught, to always go another step further and load up the circuit for additional testing if the unloaded tests pass.

Back to your car, I have another theory of what may be happening. I keep wondering why the right side vent goes warmer when you turn on the AC, but is equal to the left when the AC is off. I think this may have something to do with the extra amp draw of the compressor clutch. Both sides of the DCCV and the compressor clutch receive battery power through front fuse F32. With the AC off, the compressor clutch is not powered and the amp draw through this fuse is reduced. In this condition, the fuse is only powering the DCCV and the current flow is adequate for both internal valves to close fully and turn off all heat.

Now, let's say you've got an undiagnosed restriction somewhere in the circuit, say a loose or corroded socket in the fuse panel. As mentioned/guessed above, suppose enough current can make it through this marginal connection and the DCCV seems to operate normally when that is the only load on the circuit. But add the load of the compressor clutch and suddenly current flow drops because of this mystery restriction. The compressor clutch and DCCV are now operating at reduced voltage. The clutch slips, reducing compressor performance. The ACCM still supplies the ground to control the DCCV, but the oomph needed to overcome the spring force is reduced due to the lower voltage being supplied. The DCCV relaxes partway to the open position. For reasons unknown, the right side tends to open a little bit more and lets more heat through. This could be as simple as a little extra friction on one side, a weaker spring, or even a second wiring fault particular to that side.

Here's what I recommend doing: Backprobe the two outside pins at the DCCV connector. I think you can feed a small piece of stiff wire, maybe .030" or so, through the back of the connector. You want to be able to take a voltage reading with the connector hooked up to the DCCV. Do a voltage drop test between each outside pin and a convenient spot with battery voltage, somewhere upstream of front fuse F32. I think there's an exposed terminal at the fuse panel under the hood that should work. If nothing is handy, run a long test jumper for your meter's (+) lead back to the battery's (+) post. Connect the meter's (-) lead to the backprobe at the DCCV. Set the meter to DC volts, with a range high enough to read battery voltage. Turn on the engine, select LO, and AC off. Adjust the meter range down to read whatever voltage is present. Ideally, you should see less than 0.5V DC between these two points with the circuit under load. This is a voltage drop test of the circuit feeding power to the DCCV. Ignore any reading you get with the engine off, as that doesn't mean anything. The important number is what you see with the circuit loaded. Anything above 0.5V DC indicates a restriction. Repeat the test with the other pin on the DCCV.

Next, with LO still selected, turn on the AC. My hunch is you will see a much higher reading on your meter, indicating a restriction between those test points. If the value exceeds 0.5VDC, you've found a problem. Repeat with the other side of the DCCV connector.

You can also do a voltage drop test between the battery supply and the compressor clutch. Access is a lot poorer at the compressor, so I'd suggest checking first at the DCCV.

 

I think I covered most of this, Voltage on fuse F32 after a few minutes always 13.6V Across fuse Compressor off 18mV, with compressor 48mV. The check with the Led (actually a LED Side lamp rated at 5W) was with the DCCV connected normally and the LED
was connected between pins 9 and 10 on FC4 using test meter probes. The Voltage between the chassis and pins 9 and 10 (LO AC on) in both cases was 0.25V.
I assume this is due to the various Rs in Circuit to chassis. ON Manual, After seeing the LED Flash the First time (Left set to 63F and right set to 85F) only for about a second, and warm air started coming from the right side, After maybe 30 seconds it flashed again for a shorter time and so on for a few minutes until it stopped with very warm air. Returned cold to cold 63F, I measured the voltage between pins 9 and 10, only 1.1mV, every minute or so it went to 1.2mV for a moment. I reversed the Probes and every minute or so the voltage between pins 9 and 10 dropped to 1.0mV for a moment. All this time there was a 9F difference. I cleaned the contacts (Corrosion does not appear to be a problem with the climate here) at the DCCV with a Suede brush and electronic contact cleaner ( I repair Vintage radios for people so it is invaluable). I also sprayed the contacts at FC4 and inserted/removed the plugs a few times . Previously I measured the current to each side of the DCCV which were the same at about 900mA by increasing the
temp in manual so that one or the other opened. With the clutch engaged I had a total of 5.4A on LO AC on. Thanks to the pressure test I am fairly confident that the compressor is OK. Swapped F7 and F8 For Clutch too. I am not so happy with the Main cooling fan, I does not appear to trap a cloth like in the pictures, sure it it sucks it in but?
I had a Toyota Corolla in the Omani desert at 47 to 55C and in 2 minutes it was Icy inside with AC on Max. My neck suffered for years after. That was AC!!!!!
I am an elecrical/electronics eng but mainly with Microwave experience in circuit design and propagation and in the last 25 years transmission network design and analysis. Car A/C is a whole new field for me and being a pensioner on a lousy pension I try and stay away from the pros as much as possible. The fact of taking Pins 9 and 10 on FC4 to chassis 0V causing both vents to be at the same temperature was the winner for me. It is difficult to have cool weather here, I have a max/min thermometer outside, min varies now from 75F to 79F.
I dissed the battery today and reset everything except the 9F. My car is not quite standard as I removed the DVD reader from the NAV case in the boot but It does not seem to cause any problems.
I need to use the car over the weekend, but Monday morning I will remove the A/CCM , measure the sensor resistances at the connector to the A/CCM. Open the box and examine the PCB, If there is nothing obvious, damage caused by a previous repair etc, leaking electrolytics or what have you I will take the following step. I will disconnect the base / gate of the Right side driver transistor and reconnect it to the base / gate of the Left hand driver transistor.. This should result in both sides being the same, controlled by the front panel Left side controls.
in the meantime I will endeavour to obtain a new A/CCM.
More news on Monday
Thanks and Have a Great W/E
Mike

 

Just been out in it, 30C ouside Better with the windows open if it is not possible to keep up about 60Kph.
How much current should the main cooling fan take?
A few more details. car sat idling 5 mins, no condensation on ground, earlier after driving standing a minute or 2 a patch about 4" diam.
FromOBD2, While Idling 30mins after driving, car sat idling 5 mins, no condensation on ground, earlier after driving standing a minute or 2 a patch about 4" diam.
Int temperature 97F Verified at sensor and air is being sucked in. AC Driver Heater sensor 88F, Passenger heater sensor 100F, EVAP Air-Off Temp 88F, Calc Int temp 82F.Ext temp 82F
Cooling Fan Speed 56%
It does not appear to cool while idling and still !
Last Stupid question shouldn't the Low pressure pipe be cold instead of hot like the High pressure pipe ?

 

It's okay, we don't judge. There's no need to apologize or feel ashamed.