The disappearing heater mystery
11-04-2004, 11:45 PM
#1
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Location: Everett WA
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The disappearing heater mystery
My '92 LT1 roadster warms up all nice initially, but after about 15-20 minutes of driving the temp of the air coming out of the heater vents starts to get cold. I have to turn up the heater, the fan, etc. It seems to regulate fine early, but totally loses it.
As an aside my AC does not blow cold air (even after a recharge and some work) when its hot out. I was told that it doesn't appear to have a leak either. The vent buttons flash when I start the car, which I believe means that the AC is not charged. Could this be related to the heat problem?
- Glenn
As an aside my AC does not blow cold air (even after a recharge and some work) when its hot out. I was told that it doesn't appear to have a leak either. The vent buttons flash when I start the car, which I believe means that the AC is not charged. Could this be related to the heat problem?
- Glenn
11-05-2004, 12:28 AM
#2
Drifting
hmm could be the evaporator core. or the heater core
have a mechaic check those! also check all hoses from ac condenser for audible/visual leaks! and check the sensor right before the evaporator core.. cuz that could be giving the car a false temp!
good luck
have a mechaic check those! also check all hoses from ac condenser for audible/visual leaks! and check the sensor right before the evaporator core.. cuz that could be giving the car a false temp!
good luck
11-05-2004, 11:53 AM
#4
My car's heater went to crap and I found that there is a little plastic valve that restricts flow to the heater. Running without this valve or having it stuck one way or the other dramatically reduces heater performance.
I would lean towards something like this because you said it heats up and then gets cold. Mine would do the same thing, it would heat up but then the air moving through the heater core would cool it down faster than the coolant could heat it up.
I would lean towards something like this because you said it heats up and then gets cold. Mine would do the same thing, it would heat up but then the air moving through the heater core would cool it down faster than the coolant could heat it up.
11-05-2004, 08:55 PM
#5
Le Mans Master
If the whole panel is flashing, then there's either a poor connection or the panel is on it's last legs. If it's just an LED, then a trouble code has been stored and until it's corrected, you won't have a/c. In fact, if the a/c wasn't working before the recharge, it isn't going to work again until the low charge code is cleared. Get rid of it by disconnecting the battery.
There is a door between the evaporator and the heater core which is controlled by an electric motor. It's linkage to the motor is connected by a plastic clip. If the clip breaks, air flow can cause the door to open and shut and it will give you warm/cold air. To check it out, remove the blower module on the evaporator case mounted to the firewall. Look inside and as someone operates the temp controls - between 60 & 90 - you should see the door move. You can also push on it with a screwdriver or other blunt object. If the linkage is intact, it shouldn't move, but that may only mean that the motor is shot. To access, you'll need to remove the hush panel on the passenger's side from inside of the car. The motor is mounted on the heater box.
Unlike earlier C4's, there isn't a valve on the coolant supply to the heater core. Coolant is flowing through it at all times and it assists in cooling the engine. If the core is plugged, coolant flows over the top of it, but not through it. I've experienced a partially plugged core that would initially provide some heat, but quickly begin to blow cool air. You can try to flush it by disconnecting the lines and hooking up a garden hose to it or you can blow some compressed air through it. However, with the symptoms you describe, I think your problem is with the temp door.
There is a door between the evaporator and the heater core which is controlled by an electric motor. It's linkage to the motor is connected by a plastic clip. If the clip breaks, air flow can cause the door to open and shut and it will give you warm/cold air. To check it out, remove the blower module on the evaporator case mounted to the firewall. Look inside and as someone operates the temp controls - between 60 & 90 - you should see the door move. You can also push on it with a screwdriver or other blunt object. If the linkage is intact, it shouldn't move, but that may only mean that the motor is shot. To access, you'll need to remove the hush panel on the passenger's side from inside of the car. The motor is mounted on the heater box.
Unlike earlier C4's, there isn't a valve on the coolant supply to the heater core. Coolant is flowing through it at all times and it assists in cooling the engine. If the core is plugged, coolant flows over the top of it, but not through it. I've experienced a partially plugged core that would initially provide some heat, but quickly begin to blow cool air. You can try to flush it by disconnecting the lines and hooking up a garden hose to it or you can blow some compressed air through it. However, with the symptoms you describe, I think your problem is with the temp door.