CCU fan controller works with engine off, not when running

[swimmingpie]

I just recently repaired my climate control board on my '91, replacing all the caps and fixing any damage from the leaking goo. Before the fix, the fan only ran on high.

Everything works perfectly when the engine is off and the unit is running from the battery. The fan will run at all the various speeds. However, when I crank the engine, the fan only runs on the max speed. No other functions are affected by the engine being on. Only the fan acts up.

I'm out of ideas. If the ccu board is good and the blower power transistor is good, what could the problem be? Any help is welcome.

 

[DocL]

If you didn't use BrianK to do the repair then there is your problem.

 

[Briank]

That is interesting I am not sure how you did that. Ignition on is the same with the engine running or not. The only difference would be the battery voltage would be higher.

 

[swimmingpie]

^^^Exactly. I don't know of any other variables that could contribute to the problem. If the only difference is the voltage, you would think that the climate control wouldn't be the only thing going wrong.

 

[Briank]

When you say only runs on high do you mean it just runs on high all the time with the engine running or just runs on high?

Most likely your repair is incomplete or incorrect.

I get to rework repair from other shops from time to time and its surprising what I see even from professional repair shops like ATE who sells on Ebay.

 

[swimmingpie]

With the engine on, it only runs when set to high. When set at lower speeds, the blower doesn't run. All the other functions are fine.

I'll take another look at the board and see if I can find anything.

 

[RYU]

With the engine on, it only runs when set to high. When set at lower speeds, the blower doesn't run. All the other functions are fine.

I'll take another look at the board and see if I can find anything.

mate, are you sure you didn't reverse the polarity on one or all of the capacitors you replaced? it's easy to overlook.

 

[swimmingpie]

Update: I have been out of town this week. The fan controller is working fine and has been for about five days. Not sure what happened but the problem is corrected.