Electronic Temp Control
Thread Starter
8th Gear
Joined: Jul 2018
Posts: 8
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Electronic Temp Control
Good afternoon, I have a 94 C4 with ETC. Yesterday I was driving the car and set the temp at 75 degrees. Car was warm, then started to throw cool air. Car would warm up breifly then cool down again. Coolant temp is running normal and coolant level is fine. Anybody ever run into this?
Drifting
Joined: Aug 2022
Posts: 1,509
Likes: 429
From: Ruskin, FL
Good afternoon, I have a 94 C4 with ETC. Yesterday I was driving the car and set the temp at 75 degrees. Car was warm, then started to throw cool air. Car would warm up breifly then cool down again. Coolant temp is running normal and coolant level is fine. Anybody ever run into this?
Thread Starter
8th Gear
Joined: Jul 2018
Posts: 8
Likes: 0
I don't know what the actual temp was inside the car. All it told me was that the outside temp was 44 degrees. Also, I did'nt have it on the automatic setting. I was using it manually and thought that if I set it to 75 degrees that ot would stay there, not cool down to the point where it's actuually blowing almost cold air.
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Drifting
Joined: Aug 2022
Posts: 1,509
Likes: 429
From: Ruskin, FL
I'm by no means an expert or an A/C tech. However, here are the basics...
When you set the temp to 75°, and it's 44° outside air temperature, the ETC will automatically move the blend door from heat to non-heat when the inside temp reaches 75° (or 77° actual). Which, with 44° weather will feel like the A/C is coming on. However, it is not. Just like when you set it 65° degrees and it's 80° outside it will turn the A/C of and you get that musty smell for a minute. The job of the ETC is to keep the inside temperature of the car to the set temp. So when heat is on it will move the blend door back and forth. When A/C is on it will cycle the compressor on and off.
Having the fan set to a manual speed vs automatic only controls how hard the air blows inside the car and has no influence on the actually temperature.
When you set the temp to 75°, and it's 44° outside air temperature, the ETC will automatically move the blend door from heat to non-heat when the inside temp reaches 75° (or 77° actual). Which, with 44° weather will feel like the A/C is coming on. However, it is not. Just like when you set it 65° degrees and it's 80° outside it will turn the A/C of and you get that musty smell for a minute. The job of the ETC is to keep the inside temperature of the car to the set temp. So when heat is on it will move the blend door back and forth. When A/C is on it will cycle the compressor on and off.
Having the fan set to a manual speed vs automatic only controls how hard the air blows inside the car and has no influence on the actually temperature.
Drifting
Joined: Aug 2022
Posts: 1,509
Likes: 429
From: Ruskin, FL
This sounds like the ETC module is not working properly. This is the part I don't have expertise. But there are some diagnostics that can help pinpoint the issue.
1994 LT1 1996 LT4
Joined: Sep 2024
Posts: 772
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From: East Front Range Colorado
I m following with keen interest. The past few days, i've been researching this C68 system. Have filed away a number of links. As things stand, i know just enough to reveal how little i know (: My next step is to sit in the car and push buttons to identify what's working and not and this "test" will help narrow down if i have a vacuum issue or an electrical issue. fwiw, here is a youtube on codes that can be checked pushing C68's control buttons https://www.youtube.com/watch?v=ztXp...nel=E.T.GARAGE