1993 Heating problem
Thread Starter
Burning Brakes
Joined: May 2000
Posts: 1,097
Likes: 191
From: Vienna VA
1993 Heating problem
I have a 1993 coupe and now that the weather is turning colder, I have noticed a problem with the heat not working.
The climate control unit appears to be working correctly and all of the buttons and lights work. However, when I turn up the heat it does not blow hot air.
An additional symptom is that the fan will start blowing and then slow down. After 10-15 seconds it starts blowing fast again and then slows again.
I've done some searching and have seen posts about problems with the climate control head unit. Mine seems to be working so that doesn't appear to be the issue.
Has anyone experienced these symptoms before? Any help would be appreciated.
Thanks.
The climate control unit appears to be working correctly and all of the buttons and lights work. However, when I turn up the heat it does not blow hot air.
An additional symptom is that the fan will start blowing and then slow down. After 10-15 seconds it starts blowing fast again and then slows again.
I've done some searching and have seen posts about problems with the climate control head unit. Mine seems to be working so that doesn't appear to be the issue.
Has anyone experienced these symptoms before? Any help would be appreciated.
Thanks.
Pro
Joined: Oct 2010
Posts: 603
Likes: 45
From: Baltimore County MD
I have a 1993 coupe and now that the weather is turning colder, I have noticed a problem with the heat not working.
The climate control unit appears to be working correctly and all of the buttons and lights work. However, when I turn up the heat it does not blow hot air.
An additional symptom is that the fan will start blowing and then slow down. After 10-15 seconds it starts blowing fast again and then slows again.
I've done some searching and have seen posts about problems with the climate control head unit. Mine seems to be working so that doesn't appear to be the issue.
Has anyone experienced these symptoms before? Any help would be appreciated.
Thanks.
The climate control unit appears to be working correctly and all of the buttons and lights work. However, when I turn up the heat it does not blow hot air.
An additional symptom is that the fan will start blowing and then slow down. After 10-15 seconds it starts blowing fast again and then slows again.
I've done some searching and have seen posts about problems with the climate control head unit. Mine seems to be working so that doesn't appear to be the issue.
Has anyone experienced these symptoms before? Any help would be appreciated.
Thanks.
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
The HVAC system adjusts the fan speed based on the difference between the set temperature on the HVAC controller and the inside air temperature.
If you set the climate control to the various modes does the air come out of different ducts? If not then you might have a bad vacuum check valve.
The temperature blend door might not be working correctly. It controls the temperature of the air that comes out of the ducts.
If you set the climate control to the various modes does the air come out of different ducts? If not then you might have a bad vacuum check valve.
The temperature blend door might not be working correctly. It controls the temperature of the air that comes out of the ducts.
Last edited by Cliff Harris; Nov 15, 2014 at 10:08 AM. Reason: Corrected erroneous information.
Race Director
Joined: Dec 2000
Posts: 17,551
Likes: 26
From: El Paso Texas
Like the guys above mentioned, approach it methodically. Are your heater hoses hot? Is one hot but not the other? If that's the case, you can remove them and use a garden hose (go easy on the pressure....replacing a ruptured heater core sucks) to flush the heater core. You'll be surprised what comes out of it.
Now if both hoses are hot, ensure that the blend door is operating. There really isn't much beyond that if the HVAC control unit is sending the correct signals.
Now if both hoses are hot, ensure that the blend door is operating. There really isn't much beyond that if the HVAC control unit is sending the correct signals.
Drifting
Joined: Dec 2011
Posts: 1,254
Likes: 7
Like the guys above mentioned, approach it methodically. Are your heater hoses hot? Is one hot but not the other? If that's the case, you can remove them and use a garden hose (go easy on the pressure....replacing a ruptured heater core sucks) to flush the heater core. You'll be surprised what comes out of it.
Now if both hoses are hot, ensure that the blend door is operating. There really isn't much beyond that if the HVAC control unit is sending the correct signals.
Now if both hoses are hot, ensure that the blend door is operating. There really isn't much beyond that if the HVAC control unit is sending the correct signals.
Intermediate
Joined: Oct 2014
Posts: 27
Likes: 3
From: Florida
Same Problem with heat - solution !
I have a 1993 coupe and now that the weather is turning colder, I have noticed a problem with the heat not working.
The climate control unit appears to be working correctly and all of the buttons and lights work. However, when I turn up the heat it does not blow hot air.
An additional symptom is that the fan will start blowing and then slow down. After 10-15 seconds it starts blowing fast again and then slows again.
I've done some searching and have seen posts about problems with the climate control head unit. Mine seems to be working so that doesn't appear to be the issue.
Has anyone experienced these symptoms before? Any help would be appreciated.
Thanks.
The climate control unit appears to be working correctly and all of the buttons and lights work. However, when I turn up the heat it does not blow hot air.
An additional symptom is that the fan will start blowing and then slow down. After 10-15 seconds it starts blowing fast again and then slows again.
I've done some searching and have seen posts about problems with the climate control head unit. Mine seems to be working so that doesn't appear to be the issue.
Has anyone experienced these symptoms before? Any help would be appreciated.
Thanks.
The real issue is the 12 volt heater temperature valve (Eckler's #51595) which is located behind the passenger side lower dash bolster. You will need to remove the side dash fuse cover (inside the door frame)and 2 bolts on the fuse panel. This will release the bolster so you can carefully jiggle the bolster back towards you. Go easy as there are 4 brittle plastic tabs at the front top. Now you will see the heater valve at the very bottom held by 2 bolts. Disconnect the wire harness and drop it out. Now you can turn the heater box shaft by hand. With the inside flapper door moved 1/4 turn you should feel heat and can now verify this is the culprit. I have loads of heat now.
I posted this fix about 2 months ago and you can look it up on my john6277 posts. Good luck - and you have a GREAT car. John
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Thread Starter
Burning Brakes
Joined: May 2000
Posts: 1,097
Likes: 191
From: Vienna VA
Thank you for all the responses and suggestions. I did a more extensive test this morning and let the car get up to temperature and also drove it to work (about 25-30 minutes). It appears this may be just a C4 rookie mistake on my part.
- The car runs between 198-200 degrees when driving and 200-203 when stopped.
- I turned the climate control heat up to 90 and set the fan and controls (turned off 'auto' mode) and it was blowing warm/hot air.
- I put it back on 'auto' mode and turned down the temp to about 76.
This causes it to spend some time seeking equilibrium. The fan was not slowing and speeding like I thought. Instead, the blend was changing from the upper vents to the lower vents.
It seems to take awhile when it is in 'auto' mode to determine the correct mix and temperature. Maybe this is normal.
Thanks.
- The car runs between 198-200 degrees when driving and 200-203 when stopped.
- I turned the climate control heat up to 90 and set the fan and controls (turned off 'auto' mode) and it was blowing warm/hot air.
- I put it back on 'auto' mode and turned down the temp to about 76.
This causes it to spend some time seeking equilibrium. The fan was not slowing and speeding like I thought. Instead, the blend was changing from the upper vents to the lower vents.
It seems to take awhile when it is in 'auto' mode to determine the correct mix and temperature. Maybe this is normal.
Thanks.
