Anybody else have this problem
Thread Starter
Racer
Joined: Mar 2013
Posts: 253
Likes: 12
From: Ogden Utah
Anybody else have this problem
Heater control shows all dashes instead of OAT.
If I shut the heater of prior to turning the car off it does not seem to do this. also when dashes appear the defrost comes on full blast. Usually goes away if I restart after the car is warm.
Also it appears the left rear side of my 94 sits about an inch lower than the right. I believe I may have a bad rear mono spring, but wonder if there is any other explanation.
Thanks in advance for all your help gents! Good Day
If I shut the heater of prior to turning the car off it does not seem to do this. also when dashes appear the defrost comes on full blast. Usually goes away if I restart after the car is warm.
Also it appears the left rear side of my 94 sits about an inch lower than the right. I believe I may have a bad rear mono spring, but wonder if there is any other explanation.
Thanks in advance for all your help gents! Good Day
Last edited by Giamanut; Jan 6, 2014 at 08:33 PM. Reason: spelling
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
I have the earlier model HVAC system so I can't help you there. I suggest trying diagnostic mode:
http://forums.corvetteforum.com/1585305121-post2.html
http://forums.corvetteforum.com/1585305121-post2.html
Racer
Joined: May 2008
Posts: 430
Likes: 1
From: Austin Texas
This is purely a guess, but I would guess that your terminal conenction to the outside air temperature sensor is corroded and no longer allowing a proper signal tranmssion.
The defrost behavior reinfroces my guess, as that might, for safety reasons, be the "default' response of the heating control system when the OAT signal is lost, since defrost ensures that the windhsield gets cleared if it's cold outside.
If I am correct, cleaning the terminal connections would solve the problem.
I am out of town, so cannot look in the factory service manual to find the location of the OAT sensor for you.
Jim G
The defrost behavior reinfroces my guess, as that might, for safety reasons, be the "default' response of the heating control system when the OAT signal is lost, since defrost ensures that the windhsield gets cleared if it's cold outside.
If I am correct, cleaning the terminal connections would solve the problem.
I am out of town, so cannot look in the factory service manual to find the location of the OAT sensor for you.
Jim G
Thread Starter
Racer
Joined: Mar 2013
Posts: 253
Likes: 12
From: Ogden Utah
thermal sensor
This is purely a guess, but I would guess that your terminal conenction to the outside air temperature sensor is corroded and no longer allowing a proper signal tranmssion.
The defrost behavior reinfroces my guess, as that might, for safety reasons, be the "default' response of the heating control system when the OAT signal is lost, since defrost ensures that the windhsield gets cleared if it's cold outside.
If I am correct, cleaning the terminal connections would solve the problem.
I am out of town, so cannot look in the factory service manual to find the location of the OAT sensor for you.
Jim G
The defrost behavior reinfroces my guess, as that might, for safety reasons, be the "default' response of the heating control system when the OAT signal is lost, since defrost ensures that the windhsield gets cleared if it's cold outside.
If I am correct, cleaning the terminal connections would solve the problem.
I am out of town, so cannot look in the factory service manual to find the location of the OAT sensor for you.
Jim G
Advanced
Joined: Mar 2013
Posts: 70
Likes: 0
My 1990 has been doing the exact same thing. I can turn key off/on a few times and turn the unit to "OFF" as soon as it shows temp. Start the engine and turn AC panel back to "Auto" if temp appears. It's gotten worse since the weather got colder here in Louisiana.
I just ordered a refurbished unit from Coastal Corvette for $175.00. They listened to my explanation of symptoms and said it's most likely the head unit although the AC programmer could be at fault.
I just ordered a refurbished unit from Coastal Corvette for $175.00. They listened to my explanation of symptoms and said it's most likely the head unit although the AC programmer could be at fault.
Thread Starter
Racer
Joined: Mar 2013
Posts: 253
Likes: 12
From: Ogden Utah
refurbished head unit
My 1990 has been doing the exact same thing. I can turn key off/on a few times and turn the unit to "OFF" as soon as it shows temp. Start the engine and turn AC panel back to "Auto" if temp appears. It's gotten worse since the weather got colder here in Louisiana.
I just ordered a refurbished unit from Coastal Corvette for $175.00. They listened to my explanation of symptoms and said it's most likely the head unit although the AC programmer could be at fault.
I just ordered a refurbished unit from Coastal Corvette for $175.00. They listened to my explanation of symptoms and said it's most likely the head unit although the AC programmer could be at fault.
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Team Owner
Joined: Sep 2003
Posts: 25,394
Likes: 2,741
I believe if that didn't change things I'd run a check for codes related to the C68 functions. The FSM I believe has complete list and the procedure. I also believe the C68 control is easily disassembled and the contacts inside cleaned. I've never needed to accomplish this personally but there should be several threads regarding it.
I'd certainly try some of the diagnostics before you start throwing "parts and $$'s" at the system.
Thread Starter
Racer
Joined: Mar 2013
Posts: 253
Likes: 12
From: Ogden Utah
Good info here and i will let you all know the outcome. I am pretty sure it's the oat sensor I have a heater in blowing on it right now and in I get a reading instead of dashes I'll replace the sensor. I have packed some snow in that area driving in winter.
Team Owner
Joined: Sep 2003
Posts: 25,394
Likes: 2,741
I'd consider the cleaning of the contacts etc. for starters. Most all of these electronic controls in these cars get very little "exercise" and that's actually good for them, window switches, the DIC, mirror switches etc. I'd think benefit from "exercise"!
Thread Starter
Racer
Joined: Mar 2013
Posts: 253
Likes: 12
From: Ogden Utah
No fault codes and have not had time lately to do much but I drove it to work today and when I got there I was able to get outside temp a couple times but on the drive home it did not blow hot air through the defrost but blew cold like the ac was on. 36F outside and AC on make for a cooooooolllllll ride!
Thread Starter
Racer
Joined: Mar 2013
Posts: 253
Likes: 12
From: Ogden Utah
well Gee... I got codes off the electronic climate control. I do need help with these.
01= 86
02 =138
03=99
04=198
05=179
06=02 speed sensor car not moving
11=155
16=61
17=124
19=113
20=198
24=01
30=60
31=153
37=14
These appear to be values not fault codes per se
01= 86
02 =138
03=99
04=198
05=179
06=02 speed sensor car not moving
11=155
16=61
17=124
19=113
20=198
24=01
30=60
31=153
37=14
These appear to be values not fault codes per se
Advanced
Joined: Mar 2013
Posts: 70
Likes: 0
Well, I changed the AC head unit with a refurbished unit and am still getting the two bars on the screen from time to time.
I unplugged my OAT though and the bars appear in the same fashion as they do now. Sometimes the unit turns on with OAT displayed....sometimes it turns on with two bars on the screen.
Any other ideas? I'm starting to think it could be the AC programmer.
I unplugged my OAT though and the bars appear in the same fashion as they do now. Sometimes the unit turns on with OAT displayed....sometimes it turns on with two bars on the screen.
Any other ideas? I'm starting to think it could be the AC programmer.
Thread Starter
Racer
Joined: Mar 2013
Posts: 253
Likes: 12
From: Ogden Utah
Well, I changed the AC head unit with a refurbished unit and am still getting the two bars on the screen from time to time.
I unplugged my OAT though and the bars appear in the same fashion as they do now. Sometimes the unit turns on with OAT displayed....sometimes it turns on with two bars on the screen.
Any other ideas? I'm starting to think it could be the AC programmer.
I unplugged my OAT though and the bars appear in the same fashion as they do now. Sometimes the unit turns on with OAT displayed....sometimes it turns on with two bars on the screen.
Any other ideas? I'm starting to think it could be the AC programmer.
I also found a tread that talks about the power from the run ignition wire going to the controller through the fuse box.
It went like this measured voltage on load side of controller fuse (read low) Measured voltage on supply side of fuse and it read low!
dropped driver side knee panel found loose connection on ignition run wire corrected and problem solved.
I believe because I can have oat in the run position and engage the starter and it goes back to dashes it makes it a voltage supply problem.
Also if i rev the engine a little and cycle the key fast without engaging the starter but keeping the engine running the oat will show up.
I am going to check my fuses this weekend for good clean contact and voltage.
Race Director
Joined: Dec 2002
Posts: 13,348
Likes: 233
From: SCMR Rat Pack'r Charter Member..Great Bend KS
I actually bought a set of lowering bolts for the rear and used the additional adjustment they afforded to even the rear of my C4. Several others had said they'd tried the same method, but were unsuccessful. Not sure why it worked for me (and not for them), but it did.
Thread Starter
Racer
Joined: Mar 2013
Posts: 253
Likes: 12
From: Ogden Utah
that is interesting but on the freeway sweeping right hand turn i notice a sound almost like a u joint but goes away on sweeping left hand. I tried to adjust that side with my spring bolt but it just deflected the spring more with out raising that side. I have a 84 spring coming so I should know this weekend.