relisysxx

Just puchased a C4 cab with a few 'issues', first on the list is the non functioning heating system, or should i say over functioning! blowers do not work but the cabin is roasting hot.
I tried 'jumping' the rear fan relay which brought the rear blower on constantly (noisey though, sounds like it's got sqaure brearings).
Anyone got any clues to point me in the right direction, any help much appreciated.

tbennett017

Lots of help here... you should search for "CCU" and "Heater Box"

Does anything happen when you turn on the A/C? Does the system respond to changes in the requested temp with the right dial?

In the frunk, under the windshield, you can remove the plastic cover (allen screws) and look at the top of the heater box. Have a partner move the temp control up and down and see if any of the servos react to the inputs. You should see movement. If not either your CCU has issues, or you've got servo problems.

altarchsa

If no fans, one common problem is the fan speed control in the Climate Control Unit. Mine cuts in and out and if I tap on the face plate of the CCU with my fingertips or bang on the underside of the dash, it will come back on. You could check the operation of the fans by applying power directly to the connectors at the fans. If they're working, it could be the CCU.

FeralComprehension

If no fans are on and you have cabin heat you may find that the flexible hoses that flow hot air from the sill tubes to the HVAC unit in the trunk have failed. These can be seen behind the kick panels in the outer walls of each footbox. If my version of PET were working, I'd post an image, but....

Rocket Rob

+1 - Check the heater hoses in the foot well. The hose is a foil backed paper that can fail over time. See #16 in this diagram.



Also, read these threads.

https://rennlist.com/forums/964-foru...-real-hot.html
https://rennlist.com/forums/964-foru...ried-feet.html
https://rennlist.com/forums/964-foru...ilot-feet.html

boxsey911

Sounds like you've got a failed rear blower (this is often the reason your cabin fans don't work). Try turning the ccu to the blue dot and see if your cabin fans start working (if they do, this confirms the rear blower or its fuse is the problem). It also sounds like you've got a hole in one of the cabin hoses (as mentioned above).

hamah

Also check where that heat is coming from. If coming from the footwell area with all dash vents open and the lower slide on the CCU fully left that will also help point to a failed hose. If on the other hand the heat is from the dash vents check to see if the heat is from one side more than the other. If it is that could point to a failed or stuck temperature mixing server (also very common). You might have more than one issue.

Depending on where you live and if you can live without heat you can bypass the cabin entirely and have all your heat dumped into the rear wheel well (the system normally does this with excess heat not required in the cabin). See #11 in Rocket Rob's diagram.

Good luck and let us know how your troubleshooting progresses. Unfortunately no more answers until we see pics

relisysxx

Thanks for the replies, plenty to go and check out. When i get this sorted just have to get the roof working, get the spoiler working, get the passenger window working and get the drivers seat working, should keep me occupied for a week or two, fortunately the car is good mechanically and structurally, it's just the electrics that are shot!