DCCV Deconstructed & different views on failure of value and controller
#21
11-09-2010, 02:58 PM
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#22
11-09-2010, 03:14 PM
i know lots of acronyms but what are you reffering to as FET federal exise tax??
on the B+ it and the ac compressor clutch share the same fuse. and is ignition switched hot. the CCM(climate control mdoule) provodes ground signal to the valves to close them, theyre normally open. now if you get coolant up into the coils and the pins both positive and negative that feed each 1. youre gonna feed B+ to a modules ground circuit. most module circuity is not a high or or for that matter much able to handle any amperage. This is a prrimary reason to never use a test light, but a DVOM(digital volt ohm meter) to check circuits. a dvom is very low impedance and safe to pin cuircuits. Now if you have a cross short on the CCM ground circuits to battery power, when theyre switched to ground(active) you now have a fusible link that isnt supposed to be 1. Hense the burned circuit board in the CCM on either 1 or both legs going to the DCCV coils. to me it doesnt matter so much as where of even why, but all blown CCM's have a leaking DCCV, but not all leaking DCCV's have blown CCM's, its just a matter of time. theres a great many things I deal with on a regular basis that there NO WAY that should happen that way, but yet it does and I have to fix it. Just recently ablind spot monitor issue that shut down the CAN network, nothing wrong the the CAN network, but ended up finding a open circuit in the mirror icon. Jaguar said theres no way that can happen, yes maybe not supposed too(should have given a code in the blind spot monitor modules not shut them down) but yet it did and there was alot of wasted time checking stuff only because
"that cannot happen, it doesnt work that way" was said repeatadly. Same issue I have with a 2011 XK lic plate light going out that are module driven...time will tell on that 1.
on the B+ it and the ac compressor clutch share the same fuse. and is ignition switched hot. the CCM(climate control mdoule) provodes ground signal to the valves to close them, theyre normally open. now if you get coolant up into the coils and the pins both positive and negative that feed each 1. youre gonna feed B+ to a modules ground circuit. most module circuity is not a high or or for that matter much able to handle any amperage. This is a prrimary reason to never use a test light, but a DVOM(digital volt ohm meter) to check circuits. a dvom is very low impedance and safe to pin cuircuits. Now if you have a cross short on the CCM ground circuits to battery power, when theyre switched to ground(active) you now have a fusible link that isnt supposed to be 1. Hense the burned circuit board in the CCM on either 1 or both legs going to the DCCV coils. to me it doesnt matter so much as where of even why, but all blown CCM's have a leaking DCCV, but not all leaking DCCV's have blown CCM's, its just a matter of time. theres a great many things I deal with on a regular basis that there NO WAY that should happen that way, but yet it does and I have to fix it. Just recently ablind spot monitor issue that shut down the CAN network, nothing wrong the the CAN network, but ended up finding a open circuit in the mirror icon. Jaguar said theres no way that can happen, yes maybe not supposed too(should have given a code in the blind spot monitor modules not shut them down) but yet it did and there was alot of wasted time checking stuff only because
"that cannot happen, it doesnt work that way" was said repeatadly. Same issue I have with a 2011 XK lic plate light going out that are module driven...time will tell on that 1.
IF you feed the B+ to the CCM input, it will cause a overcurrent condition. I was trying to say that the coolant is continous and contacts the engine block so its likely to be ground which will not cause a overcurrent condtion. On the other hand, if the coil case cracks and what shorts pin (2 to 1) or (2 to 3) and its not strongly connected to ground, then it will cause damage. Since the design seems to be more robust to coolant exposure due to the potted coils and connect, I was hoping to better understand the failure mechanism and come up with a more robust test.
It would be interesting to see the resistance measurements of pin 1 to 2 and 2 to 3 in a failed DCCV as well as the resistance of the DCCV from pins 1, 2, 3 to the main coolant port filled with water on a failed part. If it does what I suspect, an engine off resistance measurements on the side of pins 9 to 10 and a voltage measurement in Lo-Lo from 9 to gnd and 10 to gnd may be able to ID a failed DCCV that's likely to take out the CCM.
Understand you pain. On your side, they tell you there is no code and it can't happen. On our side, they want next generation integrated circuits and modules to autodiagnose and selftest everything from field failures to manufacturing defects. Hopefully your feedback is understood by them so they ask us to design in the selftests that are real world relevant to hopefully make your job easier in the future.
#24
11-09-2010, 03:49 PM
Veteran Member
Did it cause any damage to your climate control??
I think CCC's and mine etc failed while externally leaking, BUT without causing any damage to the Climate control Unit, either burned traces and or transistor failures.
George
I think CCC's and mine etc failed while externally leaking, BUT without causing any damage to the Climate control Unit, either burned traces and or transistor failures.
George
#26
11-09-2010, 05:09 PM
Also, I don't know about todays prices, but it was $85 from Amazon and $4 for next day air.
#27
11-09-2010, 05:10 PM
Veteran Member
I have one that did leak externally, but Didn't take out the CCM as well. I believe CCC's leaked externally, but CCM is intact. We need to get our hands on one that DID damage the CCM, to compare and contrast to identify the point of failure.
CCC, if the gasket around the plunger seal were to be compromises, could coolant not in fact be drawn UP the coil's shaft and into the electric side of the coil?
George
CCC, if the gasket around the plunger seal were to be compromises, could coolant not in fact be drawn UP the coil's shaft and into the electric side of the coil?
George
#28
11-09-2010, 06:30 PM
Veteran Member
Re #6:
Electrical diagram may be wrong but (for 2002.5MY I think) shows on fig 06.1 DCCV pin 2 goes to fig 01.2 and via a splice/connector or two to fuse F32 (a batt+ feed, not sure whether via a relay but doesn't matter). So, pin 2 isn't via an FET or such like.
Same diagrams. 2002.5MY is the redesign, with 3 hoses etc. (It was 2003 in the USA, I gather.)
Electrical diagram may be wrong but (for 2002.5MY I think) shows on fig 06.1 DCCV pin 2 goes to fig 01.2 and via a splice/connector or two to fuse F32 (a batt+ feed, not sure whether via a relay but doesn't matter). So, pin 2 isn't via an FET or such like.
Same diagrams. 2002.5MY is the redesign, with 3 hoses etc. (It was 2003 in the USA, I gather.)
#29
11-09-2010, 06:30 PM
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My Climate control module (CCM) display flashes quickly at random times and only about 10% of the time. My DCCV is dry outside and all vents are doing what I ask....blowing hot or cold, even when the CCM is flashing. Not sure if this means my heater valve (DCCV) is fine or is this a prelude to CCM failure. Inclined to replace my DCCV (six years old) and monitor my CCM but wondering if any of you know of the CCM giving any warning prior to total failure? I've asked about this before but seeing how we're hot on this topic again I was curious about any warning signs.
#30
11-09-2010, 06:37 PM
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I think Brutal's idea that a failed/failing DCCV drags the CCM's ground up from 0V to (who knows what voltage) is worth more thought. DCCV pin 2 will stay close to batt+ over a quite wide range of currents, but pins 1/3 won't make it to 0V no matter how hard the FETs try. I don't know what the circuit inside the CCM is but if the supposed switched-gnd provided by an FET fails to go low enough (due to a DCCV fault).... Is Brutal on the right lines?
#31
11-09-2010, 06:40 PM
Veteran Member
My Climate control module (CCM) display flashes quickly at random times and only about 10% of the time. My DCCV is dry outside and all vents are doing what I ask....blowing hot or cold, even when the CCM is flashing. Not sure if this means my heater valve (DCCV) is fine or is this a prelude to CCM failure. Inclined to replace my DCCV (six years old) and monitor my CCM but wondering if any of you know of the CCM giving any warning prior to total failure? I've asked about this before but seeing how we're hot on this topic again I was curious about any warning signs.
#32
11-09-2010, 06:59 PM
Veteran Member
I think Brutal's idea that a failed/failing DCCV drags the CCM's ground up from 0V to (who knows what voltage) is worth more thought. DCCV pin 2 will stay close to batt+ over a quite wide range of currents, but pins 1/3 won't make it to 0V no matter how hard the FETs try. I don't know what the circuit inside the CCM is but if the supposed switched-gnd provided by an FET fails to go low enough (due to a DCCV fault).... Is Brutal on the right lines?
Here's the thing....the max potential voltage is 12v. Assuming the DCCV dead shorts a coil.
What I think Is happening is along the lines of either a dead short - the DCCV shorts the Supply +12v to the ground provided by the FET. The Trace on the PCB has less current handling capability than the Fuse on the B+ source, Therefore, the trace itself acts as the fuse. Basically burning out before the fuse does.
Somehow, the trace is seeing MORE current than it can handle, but less than the circuit is fused for (otherwise you'd blow the fuse first).
Two possible explanations here.
1) DCCV dead shorts a coil, fries the trace before the fuse gets a chance to react.
2) DCCV's coils resistance DROPS to a point where current is increased past the trace's limit, but below the fuses, once again frying the trace. From say 8ohm to 4 (this doubles current).
What's interesting is the reference to the DCCV B+ being on the same fuse as other sources. I'd be interested to see the current draw of a properly working DCCV. Something as simple as adding a separate fuse to the DCCV branch of the harness may be all that's needed to save the CCM from potential failure.
George
#33
11-09-2010, 07:04 PM
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Brutal,
IF you feed the B+ to the CCM input, it will cause a overcurrent condition. I was trying to say that the coolant is continous and contacts the engine block so its likely to be ground which will not cause a overcurrent condtion. On the other hand, if the coil case cracks and what shorts pin (2 to 1) or (2 to 3) and its not strongly connected to ground, then it will cause damage. Since the design seems to be more robust to coolant exposure due to the potted coils and connect, I was hoping to better understand the failure mechanism and come up with a more robust test.
It would be interesting to see the resistance measurements of pin 1 to 2 and 2 to 3 in a failed DCCV as well as the resistance of the DCCV from pins 1, 2, 3 to the main coolant port filled with water on a failed part. If it does what I suspect, an engine off resistance measurements on the side of pins 9 to 10 and a voltage measurement in Lo-Lo from 9 to gnd and 10 to gnd may be able to ID a failed DCCV that's likely to take out the CCM.
.
IF you feed the B+ to the CCM input, it will cause a overcurrent condition. I was trying to say that the coolant is continous and contacts the engine block so its likely to be ground which will not cause a overcurrent condtion. On the other hand, if the coil case cracks and what shorts pin (2 to 1) or (2 to 3) and its not strongly connected to ground, then it will cause damage. Since the design seems to be more robust to coolant exposure due to the potted coils and connect, I was hoping to better understand the failure mechanism and come up with a more robust test.
It would be interesting to see the resistance measurements of pin 1 to 2 and 2 to 3 in a failed DCCV as well as the resistance of the DCCV from pins 1, 2, 3 to the main coolant port filled with water on a failed part. If it does what I suspect, an engine off resistance measurements on the side of pins 9 to 10 and a voltage measurement in Lo-Lo from 9 to gnd and 10 to gnd may be able to ID a failed DCCV that's likely to take out the CCM.
.
#34
11-09-2010, 07:25 PM
George,
I was looking into the part, your looking into the controller. I believe both descriptions are correct. The voltage on these parts don't matter too much since B+ varies quite a bit. The main reason for a low side switch (one that shorts to ground) is that it can be driven by a 3.3V or 1.2V IC without any level shifting so its a cheaper solution.
"Two possible explanations here.
1) DCCV dead shorts a coil, fries the trace before the fuse gets a chance to react.
2) DCCV's coils resistance DROPS to a point where current is increased past the trace's limit, but below the fuses, once again frying the trace. From say 8ohm to 4 (this doubles current). "
A more wild explanation
The other harder to track down issue is the dynamic switching response. As the FET switches off, the inductor (coil) doesn't like its current to stop so it creates a large negative voltage that turns on the body diode of the FET as the energy is bleed out. May be some transient effects that weakens the copper over time until if fails like a fuse.
In any case, I didn't like the feeling of having to worry about the controller when the heat wasn't symmetric or perhaps having to replace the DCCV just because it leaks. I'll be happy to look at a few DCCV that blew the CCM to see if there is anything unique about them that may be easier to tell if you got a time bomb. I can also put them on the scope to measure the drive current and the dynamic response.
I was looking into the part, your looking into the controller. I believe both descriptions are correct. The voltage on these parts don't matter too much since B+ varies quite a bit. The main reason for a low side switch (one that shorts to ground) is that it can be driven by a 3.3V or 1.2V IC without any level shifting so its a cheaper solution.
"Two possible explanations here.
1) DCCV dead shorts a coil, fries the trace before the fuse gets a chance to react.
2) DCCV's coils resistance DROPS to a point where current is increased past the trace's limit, but below the fuses, once again frying the trace. From say 8ohm to 4 (this doubles current). "
A more wild explanation
The other harder to track down issue is the dynamic switching response. As the FET switches off, the inductor (coil) doesn't like its current to stop so it creates a large negative voltage that turns on the body diode of the FET as the energy is bleed out. May be some transient effects that weakens the copper over time until if fails like a fuse.
In any case, I didn't like the feeling of having to worry about the controller when the heat wasn't symmetric or perhaps having to replace the DCCV just because it leaks. I'll be happy to look at a few DCCV that blew the CCM to see if there is anything unique about them that may be easier to tell if you got a time bomb. I can also put them on the scope to measure the drive current and the dynamic response.
#35
07-15-2012, 07:54 AM
George,
A more wild explanation
The other harder to track down issue is the dynamic switching response. As the FET switches off, the inductor (coil) doesn't like its current to stop so it creates a large negative voltage that turns on the body diode of the FET as the energy is bleed out. May be some transient effects that weakens the copper over time until if fails like a fuse.
A more wild explanation
The other harder to track down issue is the dynamic switching response. As the FET switches off, the inductor (coil) doesn't like its current to stop so it creates a large negative voltage that turns on the body diode of the FET as the energy is bleed out. May be some transient effects that weakens the copper over time until if fails like a fuse.
#36
07-15-2012, 09:07 AM
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#37
07-15-2012, 09:56 AM
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#38
07-15-2012, 12:32 PM
Yes I have seen the post and it seems logical that a diode should protect from back emf. I have an STR with navi and once the new coolant bottle arrives I will check and see if the rccm is functioning. My inquiry was more along the lines of a root cause analysis. The idea being to mod the valve or boart to prevent me having to bruise my arms trying remove the dccv from the rats nest up front lol. I have done engine rebuilds that were easier...
#39
08-26-2012, 11:19 AM
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#40
08-26-2012, 11:23 AM
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