Car AC, electrical and engine problems?

Question

My cabin blower isn't working on speeds 1,2,3 but only runs on high.
I also found that my AC runs, on settings 1,2,3, (but not the blower), but when I turn it on high, the blower kicks on, but the AC compressor turns off, the electronic switch in my cabin for (AC) flips itself off, and the AC lines in the engine compartment freeze up.

So my questions are these. 
Would replacing my blower fans resistor restore speeds 1-3, and a further question on that.. would doing so magically enable my AC to start functioning again or is the receiver drier just shot after all these years? (its a 2003 so it wouldn't surprise me)

I also have one more pretty important question.. my car doesn't seem to know how to idle correctly anymore since this happened, so im wondering if this resistor problem might have messed up my cars CPU.. my cars cpu tells me I need to replace the forward O'2 sensor, which I did and I reset that code.. but the check engine indicator is still on, the code popped back up, and when the car is fully warmed up, it revs on its own when left to idle, and now gets horrible gas mileage.  Could it be my computer? or could it be that blown resistor somehow messing with my CPU which hurts its ability to regulate my engine?

Any experienced help would be appreciated, thanks.

paul h · Accepted Answer

Make and model? The fan speed issue sounds like a bad blower motor resistor but could also be a bad fan speed switch. I'd start by replacing the resistor since that is most common thing to go bad. That could also cause the system to ice up if there is no airflow over the ac evaporator when the system is running but could also be due to moisture in the system from a leak. Might need to replace the dryer or other items/seals and check for leaks and recharge system to proper levels.

The idle speed issue could also be related to the ac system operation since the PCM adjusts idle speed  slightly higher when the ac system is engaged to avoid stalling the engine from the added load. The PCM adjusts idle speed via the Idle Air Control motor (IAC) on the throttle body but that is also determined by the throttle settings as read by the Throttle Position Sensor (TPS) on the throttle body. IAC's can get clogged up with carbon deposits over time and act erratically as can the TPS so either of those items could cause fluctuating idle speeds. And it may not trip a trouble code/CEL light if either is defective or not working right. Or vacuum leaks can cause idle issues as well. I'd start by cleaning the IAC and throttle body bore/plate area of any carbon buildup which may be due based on the age of your vehicle and test the TPS if needed...it should have smooth changes in voltage readings as you go from closed throttle to full open...if readings are erratic, replace the TPS....check for vacuum or air intake leaks too. Might need to replace the IAC and TPS and relearn idle speeds with and without AC on.

thebax2006 · Answer

The resister pack for the blower is obviously bad since the blower only works on hi. many times the resister pack gets blown because the blower motor is bad and drawing too many amps through the resister pack Sometimes you can get away with just replacing the resister pack. If it fries again you now know why. The other problems you are having are not related to the bad resister pack. 
Make sure the 134a charge is correct in the AC system. Low 134a can cause icing. All older vehicles lose refrigerant over time.

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Car AC, electrical and engine problems?

2 Answers