dangerz

Just picked up an '03 z06. I've noticed that when I set a temperature and press the 'auto' button, it almost always blows out cold air. I need to set the temp to 90 for it to consider any hot air.

In manual mode I have to set the heat all the way up to 90 to get it to blow some hot air. Are there any diagnostics I can run to figure out what's broken?

edit: Here are the codes I get.

TCS
C1288

LDCM
B2282 Battery #1 Fault
B2284 Battery #2 Fault
B2264 Vertical Position Sensor Fault
U1064 Loss of Communications with BCM

A1 RDCM
B2283 Battery #1 Fault
B2285 Battery #2 Fault
B2263 Horizontal Position Sensor Fit
B2265 Horizontal Position Sensor Fault
U1064 Loss of Communications with BCM

A6 SCM
B0856
B0851 Battery 1 Out of Range
B2605 Seat Front Vertical Position Sensor Failure

All of them are H codes though.

striper

There is an outside air temperature sensor that is probably bad. If it is, it sends incorrect info to the climate system and it won't provide the correct air temps. It is located at the bottom of the radiator area up front underneath near the front bumper on the right side. You can see it with the hood open looking down below the headlight area.

dangerz

Thanks for the info. Do you know if there's some way to test it?

The Big Guy

Don't bother to test it. It is relatively inexpensive to replace. It is a dealer item. Very easy to replace.

dadaroo

Many things sometimes get fixed by disconnecting the battery and reconnecting it after about 30-60 seconds. It doesn't cost anything. Not sure how the outside air temp sensor would have any affect on your inability to get temps in manual. Sounds more serious but hopefully not expensive. If you don't have the FSM to do diagnostics, let us know.

BigGun

If it shows the correct outside temp then it is working fine.

dmarkshark

But, you need to drive it a bit to get the correct reading.

dangerz

Ok, so I replaced the interior sensor and it's still goofy. Any ideas?

dadaroo

Did you clear your codes and then see if any come back? If not, you need to do that to figure out where we are at. Also, did you disconnect the battery as I suggested? We need to do some simple things first before we start throwing parts at this problem. Sam

PS: Have you doen a Goggle search to see if you can find a similar problem addressed? I find that is the best way to actually search this forum. I have not looked at the FSM yet for diagnostics, but will once I get your feedback to the above. Remember too, unless you check codes while the car is running, many "active problems" will show as "H" codes.

65GGvert

Is your OUTSIDE temp reading correctly on the HVAC display?

Got uid0

As others have stated if the outside air temp reading is correct what you have is bad blend door motors (actuators) there not really actuators but that is the word to use to search this forum.

You can attempt to cycle your blend door motors by holding down the reset button on the codes in DIC. No change time to tear apart the dash, console, and pillars and i suggest replacing both at the same time.

hold reset down on 99 HVAC so it resets the motors. You most likely have a broken gear in one of them.

http://www.vetteweb.com/tech/vemp_09...r/viewall.html

Plan for 2-3 hours

Got uid0

Them temp sensor they mentioned is not the one inside the car.

It is the ambient air temp sensor and ONLY if the display of that temperature is not correct.

If it reads 30 degrees or whatever then you have corroded connection at the temp sensor.

As i previously posted it is most likely your blend door motors.

rockauto.com

http://forums.corvetteforum.com/c5-t...placement.html

dangerz

Cleared all the codes and no new codes have popped up since. The outside air temperature reads correctly. I did disconnect the battery for a couple of hours, but that didn't change anything.

After reading more, it's sounding like the actuator motors are the problem. Seems like a "fun" fix. Fortunately it's about to hit summer time in Texas and I won't need my heat, so I should be good temporarily.

edit: Just did a reset on 99 hvac. I heard the motors move. Then slow and stop. Then I heard them do the same thing (I'm assuming they're shifting from one direction to another). No codes were thrown. I tried it a second time and I heard the same thing and still no codes were thrown. I'll try the auto-ac tomorrow and see if it works.

I did check and I had the following 2 codes:

TCS
C1288 (hate this code)

A6 SCM
B2605

Got uid0

Ok Great then your blend doors are good. No codes for 99 HVAC.

THe ones you posted are not for the issue you reported.

NEXT check.... COOLANT LEAK

Is your surge tank at the proper level? The tanks are known to leak.

If there is not enough coolant in the system, the heater core will not work right and will not produce heat because there is not enough fluid circulating so it would feel like there is no heater in car

dangerz

Good to hear. I'll check the coolant level tomorrow and report back. I really appreciate all the help.

dangerz

Surge tank is low. I'm going to flush the radiator fluid tonight. That was an oversight on my part when I purchased the car. I changed the oil/filter, but not the radiator fluid.

dangerz

Ok, changed the fluid tonight. Quick test and it's blowing hot air. I'll confirm tomorrow on my commute.

dangerz

So it looks like it's working now :] Set the auto-temp to 73 today and I got warm air (it was 40 outside) until it eventually went down to the lowest fan setting. Normally, at this point, it starts blowing really cold air. This time it didn't. I moved the temperature up and down to see how it'd react and it did as it should.

Thanks again for all your help. Hopefully this closes my problem.

dadaroo

I am very happy for you. I would have never thought low surge tank level would have caused that. May have been some air in the system too that you removed. Anyway I will file that one away in my memory bank.

dangerz

Thanks man, I really appreciate the help. I wouldn't have guessed that would work either but it's always fun to learn something new :]