Scamper

Hi all,

I require a bit of advice on troubleshooting a problem i have (i have searched!).. now my heater/aircon system didnt work when i bought my car and have just got around to trying to fix it.

Anyway first call was the fuse box - no fuse in place..Aha! easy fix stick in a fuse. so this causes the fans to run constantly ignition on or off makes no difference.

Checked the connections all looks good

Is there a relay that might be stuck? Or do I need to take out the unit in the car and investigate?

Any help would be appreciated!

Ade

DrJupeman

Sorry, at first glance at this thread title I wondered what the problem was.

MisterRisky

When you say "fans" which fans do you mean? Both front HVAC fans plus the rear unit too? Do they change speed when you change the fan setting at the CCU?

Scamper

its the fans at the front of the car - they all run constantly when the fuse is put back in. There must be a short somewhere but i am not sure where to start.

There is warm air coming into the L/H side of the car (UK Passenger) nothing from the R/H side (UK Driver). Nothing seems to work on the control panel i.e no changes to air distribution, heat/cold, demist function.....

its an 89 C4 Coupe btw

TIA

DerkBarrington

I had the same problem. It turns out that the speed of the fans is controlled by the blower final stage amplifier (regulator) located behind the gas tank in the front truck. It accepts a signal from the ccu and adjusts the blower speed based on the input. The positive power to the blowers is always "hot" and the regulator adjusts the resistance to the ground on the blowers to adjusts speed. Usually, if the blowers are always on without the key in the ignition, the regulator is bad or the circuit is grounded somewhere (especially if the fans are running at full speed). The transistors in the regulator usually go bad from heat causing the problem. Hope that helps.

Scamper

Thanks!! That sounds exactly like my problem. Do you know the part number for the regulator? Is "regulator" the same terminology for a relay?

tbennett017

Are we talking about the right fans here? The two in the front bumper/wheel wells are for the A/C condenser and the Oil Cooler fan assembly. There has been a lot of discussion here about those working or not. If those are your concern, search here for "oil cooler fan" or "A/C Condenser fan" and you will find a lot of information. That circuit will run constantly if it gets an open circuit between the temp sensor in the oil cooler and the controller unit on line G12. (you can manually hack the system to run on a switch by interrupting that wire with a switch.

If you are talking about the vents inside the car with warm/cold air then I am barking up the wrong tree.. my aplogies... ;-)

DerkBarrington

The part # for the final stage amplifier is 96462401002

This part controls the 2 blower fans that provide air to the cockpit.

Scamper

thanks!

smongiovi

I have a 1991 964 - my cockpit ventilation fan does not respond at all. The fan blows at low speed only. I had the same problem 6 months ago, and I replaced the regulator Derk mentioned and it solved this problem. Unfortunately I replaced it with a used part for a cost of $200 rather than pay the $530 I was quoted for a new regulator. The part they installed is the exact one Derk mentioned above.
part Number 9642401002

Question:
Do you know if this part difficult to install? The repair shop charged me $125 to diagnose the problem and another $100 to install the part -

I'll pay the $530 for the new part but if I can install it without too much dismateling I'd rather do that. I'd just need to know how to get at the part, if I were to replace it myself.

Let me know what you think and thanks in advance.

Steve

Rocket Rob

Is it hard to install? I would say not too hard. Its been about 7-10 years since I had it out. I had to remove it while replacing one of the blower motors. Before you start investing in various electrical parts, do you have access to a scantool or hammer? It may be worthwhile to pull the diagnostic codes from the CCU.

smongiovi

Unfortunately I don't have access to the diagnostic tools. I Can bring it to a shop or dealer for that I suppose, but that of course will cost another 100 bucks. I figured since the symptoms are identical to last time, it will most likely be same cause...but that could be a mistake. I can certainly bring it in to find out for sure what the fault is.

Can you shed any light on where this part is located, and how I would access it for replacement?

Your thoughts are much appreciated.

Thanks
Steve

jimq

If some of the new guys put where they are located with their name it would make it easier for a local rennlister to help out that does have scantool and such.

smongiovi

This part sits flat on the cockpit side of the wall separating the fuel tank /tunk from the cowling area - actually closer to the fuse box side than the gas tank. Easy to remove with 2 bolts - repair shop charged $100 bucks for that... wasn't that nice of them? At least now I know for sure they were ripping me off.
anyway I'm ordering (another) used replacement part for about $150 rather than spending 500-600 on a new one. Hopefully I'll have better luck this time.

Thanks for the help.

Steve