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Found another post that documents this with pictures - https://rennlist.com/forums/cayenne-955-957-2003-2010/929076-fuse-12-in-the-waterbox-2.html
I am having this same set of issues - brake booster light, secondary air pump code/CEL, and the coolant after run pump is not running. 04 CTT. I wrongly assumed that the coolant after run pump motor died and replaced the pump. After reading this thread, I found the F12 5A fuse to be blown. I replaced the fuse, started the car, and the brake booster pump works again but the coolant after run pump still does not function in "rest mode". I could not test if the SAI pumps work as the car was already warm. Visually, the relays look fine - no corrosion or obvious defect. I have a voltmeter, is there a way to test these? Can you guys please offer further guidance on how to troubleshoot this? My car heater is very weak at idle without the pump running and it is getting cold in the NE!
Turned out to just be stubborn air bubbles in the system that even the vacuum bleeder couldn't get out. I was able to bleed it the old fashioned way with a large funnel stuck into the reservoir and A LOT of hose squeezing.
I have bled the car system several times. The uview airlift cooling bleeder worked well and did the trick for getting the air out. Pulled vac down to -25 and filled slowly, idled the car with the cap off up to operating temp, and once operating temperature was reached I put the cap back on (per instructions in the uview kit). New issue - Car only blow heat at idle. Temperature gauge is dead steady in the middle at all speeds. Anything over 2k rpm and the car starts to blow cold air. What the heck??? Could it be the secondary electric coolant pump going bad? HVAC system worked fine before the tstat and water pump replacement. As the above post shows, tstat and waterpump have both been replaced and are operational.
Hot is normal if the pump has been running for awhile. I had the same issue, all the visible connections were fine and I had jb welded them. If all the normal locations check out, there is one connection under the wiper motor assembly which is not visible for inspection. That's where my crack was and I caved and ordered new lines and an updated vac pump from an audi (same part #, diff letter at the end for newer revision).
More research shows that the cayenne's cooling system is a PITA to bleed right. Ordered the proper vac bleeder and will try again. If that fails, I will try "rocking" the car to help burp it.
I was unable to find the correct CCV without ordering trough gogal directly so I opted for compressor replacement. Picked up a used one off an 06 CS.
dpatel710 started following A/C Troubleshooting Help and SOS - Overheating after T-stat and water pump replacement
Long read but I did a lot of work and am at the end of my rope figuring out what is wrong here - I need some help! Did a major maintenance service on the 04 CTT as it approaches 200k. Replaced all the various bits on the front of the motor with the car in service position. Pulleys, tensioner, rollers, alternator, ac compressor, water pump, thermostat, serpentine belt, upper+lower radiator hoses, diverter valves, etc Vacuum bled the system and tried to burp it but it is running hot and holding at the 3rd bar. Tried the heater at max but it is only blowing cold air. Figured the coolant is blocked somewhere so I went onto to do some troubleshooting: - Checked and verified operation of the old and new thermostats in the water pipe housing with boiling water - Checked all hoses for kinks, none found - Checked coolant after run pump in drivers side wheel well. Pump is running dry, no coolant is flowing through those hoses. - To check for blockage at those hoses, I removed the hard lines and ran water through them. No block. - I then took the garden hose to the vehicle end of the hoses to check for flow, all good. - Seemed like no coolant was flowing from the water pump so I pulled the upper hose while the car was running. I figured the upper hose should spray out coolant but nada came out. Those hoses have no blockage and the radiator pours fluid out so its filling/draining. - Swapped out new water pump for old water pump again...still no dice Car was working fine prior to bringing it in for maintenance. I'm stumped and am calling on the collective brain trust for help, please! What do you guys think it could be/have any troubleshooting tip? Can someone color in info on how the cayenne cooling system works? I understand the basics for a normal car but the CTT has a bunch of extra stuff in it.
I replaced the compressor and dryer, all is well now. Before replacement - low side was around 35, high 150. After replacement - low 30, high 175.
This may be of help -
Gotcha, I will try the CCV rather than a used compressor as my next step. Thank you for the help!!
I ran into trouble with this too - ended up using NGKs website and their recommended plugs. My CTT had 4 prong plugs in it from the PO. I switched back to single prong - didn't notice any difference although the 4 prong ones were def due for the swap when I got to them. I ordered a coil pack kit for my CTT and it came with the single prong plugs for the NA V8 and those were gapped to 1.6mm. I returned the plugs and then ordered the NGK recommended plugs for the turbo which came gapped to 0.8mm....Although their website doesn't reflect this difference.
Thanks Brett! I did see your past posts and this is next on the troubleshooting list. I tried a deep vac and recharge by weight, replaced cabin filter, then replaced the condenser fan and relay. The car fooled me and the ac seemed to be working better after the fan replacement but it was just cooler weather at the time. Still no real improvement but I have noticed that the AC will randomly blow ice cold on long road trips - leads me to think its something going on with the compressor. When I did the recharge, at idle - low side 32, high at 150. Around 2k rpm, low was 40 and high at 170. High side pressure seemed low to me.
My a/c went from working well in the sweltering Florida heat to barely keeping the cabin cool on 80F days. First check of the low side was at 35 with ambient temps around 75F. A tad low but still within range on the gauge I have. Tried topping it off to 40psi and the vent temps actually jumped up a few degrees. VCDS shows no faults for hvac and measuring blocks show positive voltage, load, and rpm's for the compressor. The vents blow around 55F at LO with the outside temperature around 75F. While checking the low side pressure, I did notice that the condenser fan is not as loud as it used to be. It seems to be running on low vs. high where it sounds like a small aircraft taking off. Is there a low pressure switch/relay or is this a fan issue? Can anyone please offer some guidance? I haven't had to work on a/c systems too much so its something to learn for me. Thanks!