Brrrr! Q THINKS it is blowing warm air

[DMHinCO]

My 1994 Q45 decided to stop blowing warm air from the heater. It blows cold air on my feet very hard if I set it to 85deg. It blows through the dash vents as I lower the temp to cooler than cabin temperature.

Possibly related: When car is warm and I am stopped at a light, I hear a series of sounds that sound like they originate from the right front tire area (?!). Each sound lasts less than a second and they are separated by two or three seconds. It sounds like an electric motor is trying to activate something, failing, and trying again.

Any ideas on what this might be before I take it in? I'd love to fix it myself if I could. Money is a bit tight right now. And mornings in Denver have been a bit chilly.

I have done a search and I found this thread but not much else. Apparently, I can access ECMs (whatever those are) and Technical Service Bulletins for 24 hours for $20 but I don't even know what I am looking for.

A little help please? TIA.

[maxnix]

Look for a broken air control door. Lots of labor to get to unit under dash. Might want to get that downloaded manual and do it yourself. You can buy some nice tools for the 8-10 hrs of dealer labor charges.

That's my guess. Let's see what Q45tech says.

Welcome to the club. Please tell us more about your car when you have time.

Might do a search on heater core or AC to see discussions about this type of failure.

[Jeff Williams]

Verify, that the unit will switch between defrost, vent, floor/vent, and floor. If it does this fine, but just blows cold air, unless it is set to 85 degrees, it could be your plenum temp sensor. That is what the dealership had to replace in my wife's 2000 I30t.

The A/C worked fine, and all the dampers moved fine, but the system would not allow hot water into the heater coil, unless the setting was on 85 degrees. I could set it at 84, and the air would start to get cool again.

I don't know if this is the same problem, but it might be worth a check.

Definitely get the servcie manual and the TSB's. I don't have them, and am at the mercy of those that do. Begging usually works.

[911/Q45]

I just came in from the garage fixing this problem. My HVAC was blowing cold when it shouldn't and the self test program showed no faults. I looked at the shop manual and it led me through the maze ending with the engine temp sensor. That $20 part actually feeds data to the ECU and the HVAC. The bonus is that my intermittent CEL and rough cold idle is probably cured too! The only tough part is you need a 19mm crowsfoot wrench and the sensor for the dash temp gauge has to come off first. If you do it when the car is cold, it doesn't even leak coolant. The sensor is located under the top front plastic cover that hides some fuel lines and the front two injectors. It is in the coolant housing behind the small cap near the upper radiator hose. It's really satisfying to solve something like this!

[HeavyDuty]

My hvac works intermittently, no clue what makes it work or not, though it seems to like cold weather better. If it's hot outside, neither the a/c or heat works.

I noticed when it's acting up it THINKS the ambient temp is something goofy like -70 deg.

When it works ok, the ambient temp is correct.

[Q45tech]

Never seen a coolant temp sensor fail unless corroded connections on sensor/connector or a scale build up insulating the sensor from the dirty acidic coolant.

A little extra resistance is significant since at 176F it should read 300-330 ohms at the ecu pins or sensor output terminals........680 ohms at 122F..............2,100-2,900 ohms at roughly 68F.

[911/Q45]

Heavy Duty-The ambient sensor is also used by the HVAC and is located under the plastic shroud by the hood latch. I'll bet you can fix your problem cheap if you replace it.

Q45tech-The coolant temp sensor on my car had clean contacts and the wet side wasn't shiny, but not thickly coated either. The tech at Scottsdale that I spoke with had seen several failures.

[DMHinCO]

Resurrecting this thread.

maxnix, you were right, according to the dealer. Broken air mix door. $1700 with parts and labor for the dealer to fix.

I wonder how much those cameras are that they use in surgery. I wish I could go up the vent and flip the door until summer.

Too expensive for me. Heck, my car (94Q w/90Kmiles) isn't worth much more than that. So I continue to shiver.

[maxnix]

DMHinCo, if you can spare the down time and are patient, you might be very pleased to do it yourself over a week or so. No other fix has been posted, at least that I have seen.

Think of your nifty new tool collection!__________________Brian1995 Q45 & Q45t & 2000 Q45

Discover the power of the button!

[elwesso]

I agree..

Just because it costs a lot doesnt mean its hard..... I dont think anything in that area would be too terribly difficult..

THe japs just like to pack things togther tightly which makes doing things like this no fun, and somewhat painful.

I STILL have scratches on my hands from the plenum and knock sensors!!!!

[Q45tech]

OH, I would say removing the dash and reassemblying all connections correctly is more difficult than a plenum job/guide job any day.

It really does take an expert all day and many times it drags into the next day...........15 hours labor is cheap..........we charge 15 hours x $70 plus the cheap part.......around $1175.

The albatross of the 94-96. Not too common we might have done 5 in 3-4 years. Caused by not exercising the system in summer and winter so the door surround sticks and breaks the mounting pins.

[DMHinCO]

Caused by not exercising the system in summer and winter so the door surround sticks and breaks the mounting pins.

I'm not doubting that this is the usual cause. But here in Denver, there is never a month in which I don't use both the heat and the AC. Often, it is in the same day.

Well, now I don't. AC only for me. And my wife bought me a heating pad that plugs into my cig lighter. The thing gets so hot it roasts my, uh, man parts. :oface

[Q45tech]

Easy to check the problem using FSM diagnostics: step by step electronic checking of all HVAC functions without Consult.

The servo position motor will say [report the position] it moves the heater door but you don't feel/hear the door move.