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i've recenlty bought a 2004 S type v8 4.2 (presentation to come) but i got a very strange problem today.
i was driving with A/C on and working fine 19° inside and 30 outside :-) and SUDDENLY the air blowed by the car became VERY hot ! i tried to set temp at "lo" or "hi", with or without A/C, different temps by side, etc but there was NO difference, the A/C system was still blowing very hot air on both sides...
i've heard about CCV but i couldn't manage to find it under the bonnet... (the V8 is really BIG and hides everything around it)
thank you for your help because i actually can't use my car
Good troubleshooting so far. Next step is to determine if the air from the vents is warmer or cooler than ambient air.
This guide will walk you through how to diagnose the problem. Check the DCCV as described in post #2. After that, depending if you’re getting any cooling or none at all, proceed to the next applicable step.
I didn't manage to test the DCCV...it was really impossible having some place around the engine. I tried by the top but i would have had to unplug a big hose and drain cooling liquid or by the right wheel but i didn't have enough place to unplug the connector...
I also couldn't really test the temperature of blowed air because the engine was getting hot to quickly and letting hot water going by the DCCV without being stopped - ok so it means that my DCCV or my A/C controller are dead ? - in fact the three hoses going from the DCCV to the interior were very hot 1 or 2 min after i started the engine...
Measure the voltage, resistance, and/or current at the brown/green (NG; FC4-9) wire, then at the brown/white (NW; FC4-10) wire at connector FC4. Applies to VIN M45255 – N91220 only (presumably for the 2003-2008 model years)
i get 14v on each connector, with A/C on "LO" or "HI"
i get 0 ohms on each connector, with A/C on "LO" or "HI"
Yep. Based on what you’ve done so far, my conclusion is you’re in FullPanicMode(tm).
Deep breath. This is a very common problem. There are several possible reasons, though, so don’t just start throwing parts at it.
Pour yourself some coffee. I’d suggest decaf. Maybe some nice soothing herbal tea. Go back to my first reply, in post #2. Follow that link. Read post #2 in that guide. It describes how to check the DCCV operation with a $3 pocket thermometer in the dash vent. If you don’t have one of those thermometers, any grocery store has them in the baking supplies. You’ll be spinning your wheels without one. There is also a fuse to be checked.
The wiring checks you did? Where did those come from? I’m in the middle of a long camping trip with spotty cell coverage, so have no way to view the PDF wiring diagrams. Note the method I gave in my troubleshooting guide doesn’t require any initial wiring checks for DCCV. Only after a fault is confirmed would you need a meter to determine if the valve itself or the command signal is the problem.
Remember the DCCV is spring-loaded open. The idea is to allow maximum heating in the event of a failure. This makes sure the defroster is always available for safety. Fogged windshield = dangerous. No AC = inconvenience
Also, you never answered about the duct temperature. It’s VERY important to know if it’s cooler, warmer, or roughly equal to ambient. Don’t guess. Spend the $3 for the thermometer to know for sure. That will tell you how to proceed with troubleshooting.
Air is MUCH warmer than exterior !
Air is a little warmer at left than right side
i can't say if a/c is still working because the engine temp grow quickly and DCCV stay opened so there is hot air into the car 1min after engine start...
but the day before the fault a/c was working perfect so there isn't a leakage problem or something like that.
Air is MUCH warmer than exterior !
Air is a little warmer at left than right side
i can't say if a/c is still working because the engine temp grow quickly and DCCV stay opened so there is hot air into the car 1min after engine start...
but the day before the fault a/c was working perfect so there isn't a leakage problem or something like that.
Please make sure to follow the test setup exactly as listed in post #2 of the troubleshooting guide. To test the DCCV properly, the AC must be OFF and LO displayed on the control panel.
I’m not sure how you’ve got the panel right now. If set up as described above, a properly operating DCCV will NOT heat up the air in the ducts. You should see temps very close to ambient.
Do not worry about the actual AC system right now. It could lose all refrigerant, the compressor could blow up, and tweakers could steal all the AC components for scrap metal. Meanwhile, the duct temps should stay close to ambient as long as the DCCV is commanded closed (LO selected) and the DCCV is responding properly.
Did you ever check that fuse? After that, run the electrical checks at the DCCV connector. If no ground at the two outer pins, a failed DCCV may have also damaged the control panel. This is a very common situation on 2003+ cars. The troubleshooting guide has a link to a company that can repair your panel for a very reasonable cost.
Don’t panic. Many people have experienced the same problem. Work through the guide exactly as written. It is designed to take you to the correct diagnosis with minimal effort. Don’t flail around and get sidetracked with things that don’t matter at the moment
Rather than gamble on a used part that may have the same hidden damage, they can rebuild and upgrade your existing panel with a two-day turnaround. Best of all, they add an automatic overcurrent feature that the original should have had.
i m currently reading some topics about DIY repairing.
You may find some references to a jumper wire repair. It will likely work fine at first, but eventually when (not if) the DCCV fails again and overheats the controller, you’ve now got a MAJOR fire hazard. Instead of a fine circuit board trace that will open up and stop the current flow, the jumper will keep the overload going:
My thoughts on a jumper repair? Add an external inline fuse in the common feed wire to the DCCV.
Originally Posted by tibam13
" Sounds like a textbook failure. " i did not understand (sorry english is not my native language !)
Oh, that’s just an expression. It means many, many people have had this situation. It’s so common that if taught in school, the situation is so well-known that it would be in the schoolbooks.
i have temporary repared my ccm by doing jumping wire and it WORKS, my a/c is back :-). I understand that kind of repair can do major damages on ccm if the dccv goes bad again so i ve changed it too and i will find a other ccm on days/months to come in order not to keep mine in the car with that quick repair.
To reduce the risk i used small wire and remove half of the section into the wire to be sure (or pretty sure) that if there is an high intensity amp because of dccv fault, wire will break before burning all the ccm...
One other point to always bear in mind is the temperature gauge on the instrument cluster is NOT to be relied upon when an engine overheating condition may exist. The gauge needle stays in the middle from 86 C to 129 C, which is not good for the engine.
Use the OBD port with a Bluetooth adapter then download and install the Torque app on your phone to see the actual engine temperature.
S-Type V8 A/C suddenly blow very hot air
