I don't have a good answer on the current draw for the fan. Rather than test the fan itself, the easiest thing to do is see how the AC behaves when the fan isn't needed, above 30 MPH or so. You've got plenty of ram airflow through the condenser above that speed. If a weak fan is the root cause of poor AC performance, all would be good at higher speeds, but it's not. The fan could still be part of the equation at lower speeds, but for now I'd concentrate on the poor cooling under optimal conditions, that is higher speeds (good airflow) and the compressor spinning at a good speed.

The condensation you've observed may be okay, especially in a dry climate. This isn't a foolproof test, more of a generality. No condensation is bad, or a big puddle well after shutdown. Both of those conditions point to excess ice on the evaporator. I'd still compare the resistance of those three temperature sensors, though.

Re: The cold pipe - I think the cold portion is only going to be between the thermal expansion valve (center of the firewall) and the evaporator. In other words, buried inside the dash. Unlike other cars, we can't observe if this line is getting cold.

Have you checked the compressor clutch for slippage yet with the paint mark test? I'm still wondering about that. A worn-out clutch isn't an exotic failure by any means. This is one of the basics we haven't ruled out so far.

Back to your DCCV: I think it would be really helpful if you could physically block off the coolant flow during a test drive. IIRC, you've only done that for an idle check while parked. Remember, coolant flow to the heater is marginal at idle. Maybe the DCCV is letting lots more coolant through at higher engine speeds. I wonder how your AC would behave on a test drive above 30 MPH with the heater return line blocked off. You've mentioned you're hesitant to do that, but I'm sure the pliers could be safely secured out of the way with some heavy duty tape or something similar. Or if that is like fingernails on a chalkboard to you, disconnect and cap/plug the lines. Or put a marble that fits snuggly inside the flex line and leave everything connected, as long as you can remove it later. My basic thought here is to physically block off the heater lines for now, so you can continue troubleshooting the rest of the system without any possibility of heat skewing your results.

I'd suggest the paint mark test first, though. Remember, this compressor has an internal pressure regulating feature. Not 100% sure, but it may sacrifice volume to maintain the regulated pressure. The pressure may seem good, but the resulting low volume will cause poor cooling. Check the drive belt tension, too. That's another possible cause making the compressor run too slowly.

 

Anybody else have any thoughts on the matter? I get it, I'm the guy that literally wrote the book (aka troubleshooting guide) on the subject. But it seems the thread has turned into the Mike and Karl show. I'd hate to think we're missing something obvious, or even worse, I'm less correct than usual. If anybody else has any ideas, please chime in.

My TheoryDuJour is to figure out why the cooling performance is so poor under optimal conditions. That's freeway speed, with good RPM at the compressor and plenty of ram airflow through the evaporator. Physically block off the heater return line for all of this testing and leave it like that for now, to eliminate any possibility of uncommanded heat reaching the cabin. Leave the temp setting at LO to rule out faults from the automatic control side.

Once good cooling is reestablished under ideal conditions, we can reintroduce other factors (one at a time) that may also be present under other conditions. Those are my thoughts, anyway, subject to medication levels and wind direction.

 

Retired but an Ohm is always an Ohm
Cheers
Mike

 

Tomorrow paint test. Then I will use a small vice to block off the hot hose and tie it to the chassis. Unfortunately the valve remains hot because the 2 bottom connections pass hot water. True without any flow there should not be any heat transfer to the core. Good rpm is going to be around 1500-2k. Serpentine belt changed about about 14kkms ago.Looks !!!!! OK he said!!!!
Temp sensors Tuesday morning measured at the A/CCM connector. Working in the car in the afternoon under the sun is not very pleasant.
Sorry for the hassle Let you know what I find tomorrow pm
Thanks for your help.
Mike

 

OK, Put the vice on the hose, Ambient temp 81F, normal running traffic etc temp in vents 70F also at idle. Running on motorway at 100Kmh 50F
Running at 100KMh on Motorway with AC OFF 86F, 5F more than ambient, (See below.). On return home Clamped hose was cold/Ambient temp.
This is a diesel I cannot see the compressor from underneath the car even with radiator shield removed. I will try white spot test when it gets darker
from above and maybe with endoscope manage it.
It is only possible to see the end of the clutch from above. This is a real pain compared to its petrol brothers. Pulls in with a nice click! I could maybe add some volts 3.6 or 7.2 to the clutch supply or use an external supply to see if idle performance improves. Obviously I don't want to burn out the solenoid coil so current would need to be monitored closely.
Results were the same as connecting the FC4 pins 4 and 9 to chassis a few days back so a clean bill of health to the DCCV.
50F doesn't seem very good at 100kph? About 1400rpm.
How do you check belt tension, is it Preset?

 

50F is not good. That tells us the AC is kinda sorta working, but not very well. You should see down around 38F at freeway speed.

50F is somewhat encouraging, though. Generally it means you have no major faults, just something (hopefully minor) limiting efficiency. The fault(s) could be as simple as low refrigerant, a bad evaporator temperature sensor, a slipping compressor clutch, a slipping drive belt, condenser clogged with bugs, etc.

For the drive belt tension, please see post #18 in the troubleshooting guide:

https://www.jaguarforums.com/forum/s...2/#post1934020

That's for an early V6, but I believe all models have something similar. The belt tensioner isn't fixed, but has a heavy spring at the pivot point to maintain a certain tension on the belt. If hard to see the marks, try pushing on the belt midway between two pulleys. There shouldn't be too much give when pressure is applied.

Try some belt dressing and see if that helps. See the details (linked above) of how it worked for me, with nearly identical symptoms.

Been wondering about the refrigerant quantity. You had the system professionally serviced, a full evac and recharge. Unless the system has some major leak, the quantity should still be good. But is there any chance the shop had the wrong specs? Does the diesel model take the same quantity as gasoline models? Just wondering if there was a mix-up somewhere in the process.

 

Hi Karl, The spec is for the gas is under the bonnet, 700gr +/- 50.
Today I was told about an honest company that specialises in car A/C systems. They wanted me to come back next week.
I gave them the sob story and asked them to check what was the matter, They checked the belt, Clutch slippage with a strobe.
All OK. Airflow stationary at idle. Hooked everything up to their gauges and checked at Idle, 1500 and 2000 rpm..

2 guys, unanimous opinion "Worn out Compressor". They had nothing to gain because they knew full well that I would take the car back

under guarantee. They charged me 10 Euros with a receipt.... It has only covered 4000Kms since I got it thanks to Covid. I would have taken
it back before but it is about 70Kms away and I am sure the car will be away for several weeks. I will get them to sort out some of the minor probs too.
But not the 5C difference or I will never see the car again.
Thanks for your invaluable help and advice.
Mike

 

Yeah, they're probably right. As AC experts, hopefully they should be familiar with the Visteon compressor and its internal pressure-regulating feature. It behaves differently than a traditional on/off compressor, and could give a misleading indication of failure if unaware of the differences.

My M.O. for troubleshooting such a compressor has been to rule out any external factors until you're left with nothing else. Is this the best way? Heck if I know, maybe not. For your situation, dealing with this shop, the best tactic might be to agree ahead of time what happens next (and especially who pays) if a new compressor isn't the fix. I'd hate to see you paying for their expensive albeit educated guesses.

I'd still check the resistance of the evaporator temp sensor. This is easy to do from the ACCM connector, and won't cost anything but your time.

The strobe light is an interesting method to check for clutch slippage. That's more comprehensive than my simple paint mark test.

Do you know how they ruled out a slipping belt? Did they just check the tension and call it good? I'd still suggest trying some belt dressing and see if that helps. If the belt was glazed, it can still slip even with the correct tension.

Have you considered doing the piston mod on the compressor? I wonder if this might help. Could be the rest of the compressor is fine, but the regulation feature is acting up. Details are in the troubleshooting guide. Haven't done it myself, but supposedly it is fairly simple and can be done in situ. The only downside is you must do a full evacuation and recharge. It's worth a gamble if doing the work yourself, but probably not if paying someone.

 

Well the "Guessers" as you put it wouldn't be doing the job in any case. The belt check was visual and by hand. I sent an email to the Co where I bought the car this morning, should still have 5 months guarantee left, Haven't replied yet! If they are willing (Obliged) to do the job I will see what happens, I have already told them it is the Compressor obviously they are not going to take my word for it. Unfortunately when I got it in December, the air came out colder so naturally assumed it was working, Could have been the last straw for the guy that sold it having been through a hot summer. Changing it on the diesel is a bit of a bummer from all accounts.
Whatever happens I will post progress
One thing I did note was that the air was cooler if the blower wasn't full on by a degreeC or so, it was as if there was not enough cold was being produced, same thing I guess.
Quote:-" I'd still check the resistance of the evaporator temp sensor. This is easy to do from the ACCM connector, and won't cost anything but your time". Should this be doing anything on LO? I will check all 3 when I get the chance. ( I know there is a prob with the control box re the 5C difference left to right.) I will sort that one later.

 

Yes, even with LO selected, the evaporator temperature sensor is active. It sends a signal to keep ice from collecting on the evaporator, no matter what mode is selected. It's one of the main inputs to the controller. If the sensor is reading low, it will shut off the compressor too early. If reading high, it will let the compressor keep running and let ice accumulate. I think, but am not positive, that if the compressor isn't shut off normally by this important sensor before ice builds up, the compressor's self-regulating feature reduces the output. That's why I'm a bit concerned of a possible misdiagnosis saying it's a bad compressor, when it may be responding exactly as designed.

Remember, the evaporator temperature sensor is the same part number as the other two temperature sensors for the outlet ducts. Those two sensors are only active in automatic mode, but not in manual. Let the car sit for several hours so the temperature equalizes for all three sensors. The resistance readings should be very close. The troubleshooting guide has a chart with expected resistance values for a given temperature.

 

From the ICsoft I930 OBD2 reader there are 3 sensors associated with the AC, There are some others too, solar etc.
1, AC driver heater sensor 88F
2. AC Passenger heater sensor 100F
3.Evaporator air off temperature sensor 83F
cabin temperature 97F
These are actual readings I got one day, 1 and 3 are always fairly close.
Just what exactly is Evaporator air off temperature, what does it mean, I don´t think much ice will be formed on it at 83F !
Tomorrow morning I will measure the temperatures on the analyser while it is all off and they should be all the same around 77F and then start up on LO and record again
the readings.
By shutting off the compressor there is only the clutch, Correct? I have never seen it disengage it is always running with the AC
on Auto LO.
One last point They changed the unidirectional pulley on the alternator a few months ago after it sounded like a tree full of birds. Maybe a better look at the belt
and some of whatever it was that you put on it.

 

This Morning ambient 77F, 40% Hum.
Engine off Clima off.
1, Evap sens 75F
2. Driver sens 79F
3. Pass Sens 79F
Engine Idle Clima Auto LO
1, Evap sens 64F
2. Driver sens 66F
Engine 1500 rpm
1, Evap sens 61F
2. Driver sens 60F
Engine 1500 after 2 mins stable
1, Evap sens 46F
2. Driver sens 46F

 

Boy, it seems like you're getting within spitting distance. Were these values recorded with the car stationary? Can you get a reading with the vehicle in motion, preferably at freeway speed so you've got plenty of ram airflow? You may need a helper to watch the scanner while you drive.

 

Yes, that is correct. There are three systems that work together (theoretically) to keep the evaporator at the desired temperature, just above freezing. I'm not sure if one of them is considered primary, and the others are backups, or if they are all equal. Just a hunch, but I believe it's possible for a minor fault in one system to be hidden by the others. If the AC output was erratic, you might even find them fighting each other, but that doesn't seem to be your case. So in no particular order:

1) Thermal expansion valve: This regulates the flow through the evaporator, via an internal bellows that reads the temperature of the refrigerant leaving the evaporator. This has no direct control over the compressor clutch.

2) Self-regulating compressor: This is the spring-loaded piston doohickey that reduces pump output when the pressure gets down to the proper range. Jaguar issued an optional service bulletin to override this feature, and trick the compressor to always run at full output. Again, no direct control over the compressor clutch.

3) Evaporator temperature sensor: This sends an electrical sensor to the ACCM. If the evaporator is too cold and ice can accumulate, power to the compressor clutch is switched off.

Because your compressor isn't shutting off, the evap temp sensor is not sensing the temperature is too cold. This does NOT mean the sensor is good. The sensor could be inaccurate and reading high, and not shutting off the compressor clutch when it should, before too much ice can accumulate. The scanner values you've recorded show the this sensor and the other two tracking fairly closely together, so maybe this isn't it. But it would still be VERY helpful to check the accuracy. Remove this sensor and compare the resistance to the chart values at various temperatures, especially around freezing. A cup full of water and ice cubes would make a good test, probably close to freezing. Measure the water temp to be sure.




That's another big clue right there. Even if the belt tension is good, it may be glazed over and slipping. If the belt is glazed, you get a double whammy. First, the belt slips relative to the crankshaft pulley, so the belt is not moving as fast as it should. Then the compressor pulley also slips relative to the belt, so now the compressor is running quite a bit slower than designed.

Please see this again, and how my AC behaved with a drive belt problem:

https://www.jaguarforums.com/forum/s...2/#post1934020


At the very least, I'd certainly try some belt conditioner and see if that helps. I'd sure try that first before gambling on a new compressor. Here are a couple of brands:

https://www.permatex.com/products/lu...g-conditioner/

Prestone | Products

I'm sure you could find something locally at any auto parts store. Some sources say not to use anything on a serpentine belt, but I have had no problems. In fact, the second link above even shows a serpentine belt on the can.

I don't know, I'm just kind of skeptical of those two guys condemning the compressor right away. From my personal experience with multiple vehicles, the compressor itself is very robust. The clutch wears out and slips. Or I've had an electrical issue reducing current to the clutch coil, so it didn't clamp down 100%. And I've had other faults that made the compressor look bad. The only time I've had a compressor itself go bad was one that was leaking externally, but other than that it performing okay. So from my over-rated personal opinion, a compressor problem is way down on my list of things. The compressor's interal pressure-regulator mechanism may be acting up, but that is easily corrected with the service bulletin.

Have you considered buying or renting a vacuum pump and service manifold, so you can do the work yourself? After further testing of the evap temp sensor, and trying some belt dressing, I'd say you're a prime candidate for the compressor modification. I do all of my AC work myself, and that's what I'd try before replacing the entire thing. Probably not worthwhile to take such a gamble if paying somebody, but it's a reasonable stab if doing your own work.

 

Belt Dressing/conditioner is very hard to find here, I saw a can in a shop window about 30K from here on Monday, so tomorrow
That is our first stop and then get back here and try it. You cannot find the DIY A134 gas bottles either. Tools are also very hard to
come by, especially Torx and eTORX. There are no diy car repair or custom shops, Maybe it is forbidden to work on your car here like in Italy.
There you can only do what is in the owners manual, More than that carried a 500 Euro fine and that was 10 years ago, Same with a tv
antenna only a registered technician can install it. When I set up a steerable H-H 2.5m dish that I had scrounged in 1986 I had all kinds of bother,
Starting with the Concrete block. That's another story but it is still trying to guarantee jobs for the boys.

 

Ok managed to get it," CYCLO Heavy Duty Belt Dressing" ( Not for serpentine Belts) Will spray the ridged part for a few seconds while the engine is idling.

 

I've had good results applying the dressing with the engine off. Just spray it on the inside of the belt wherever it is convenient. Once you start the engine, it will distribute itself fairly well. It doesn't take much.

If you try to apply with the engine running, the fan tends to blow it away. In addition, it can be dangerous to get your hand so close to the moving parts.

Fingers crossed that you see some improvement.

 

In the Cool Of the Morning I'll be a Sprayin!! n Hopin!!

 

After applying the belt dressing, see if your steering feels lighter. Heavy steering (power steering pump turning slower than normal) is another symptom of a drive belt that is slipping.

 

Bad News, no difference, almost impossible to not get overspray, Sprayed in several places short bursts and then rotated engine without starting and repeated. Ran engine for a few minutes then went for a short run 5k at up to 80Kph temp did not drop below 60F and going under 50Kph returned to 68F Ambient 77F No noticeable difference in steering either.