92 SC300 heater problem
12-26-01, 04:21 PM
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92 SC300 heater problem
I'm a new member of this forum. I've read enough to understand that surely I'll find an answer to my question here.
The problem is my 92 SC300 heater is acting up. It seems to surely be "fixable", but at a price I'd rather not pay. Can any of you point out a possible "work around" for this?
Symptoms: heater ALWAYS works properly when the car is cold. If I go out and start it up on a freezing morning, the fan properly waits until the water in the core is warm enough and then gradually picks up speeds as the core temp increases.
But if I stop and turn the motor off, even for a few minutes, and then resume the journey, the heat will frequently fail. Most of the time the fan will come on immediately even tho there is no warm water in the heater core. No amount of turning the heat off and on, manually controlling the fan or "recirculate" has any effect when it gets in this mood.
After doing a search on this problem on deja.com I found out some people were able to "bypass" this problem by disconnecting an air line leading up to the heater control valve (which I believe to be a small circular cylinder with at least one "vaccuum line" and an electrical lead) attached high on the firewall on the passenger side of the engine compartment. Disconnecting several of these, one at a time, during a problem period did nothing to assuage the coldness.
So, unless one of you has a better idea, is there a way I can replace the valve with a manual valve? Even if I have to get out of the car, open the hood and adjust the valve to my needs, it would be a better, cheaper solution than the $300 that a new valve costs. This should work even if the problem is actually some computer chip that commands the valve. And that's about as much money as I want to put in this car with 172k. I'll probably sell it this Spring.
But I'd like to hear of your comments first. Thanks in advance for any help!
The problem is my 92 SC300 heater is acting up. It seems to surely be "fixable", but at a price I'd rather not pay. Can any of you point out a possible "work around" for this?
Symptoms: heater ALWAYS works properly when the car is cold. If I go out and start it up on a freezing morning, the fan properly waits until the water in the core is warm enough and then gradually picks up speeds as the core temp increases.
But if I stop and turn the motor off, even for a few minutes, and then resume the journey, the heat will frequently fail. Most of the time the fan will come on immediately even tho there is no warm water in the heater core. No amount of turning the heat off and on, manually controlling the fan or "recirculate" has any effect when it gets in this mood.
After doing a search on this problem on deja.com I found out some people were able to "bypass" this problem by disconnecting an air line leading up to the heater control valve (which I believe to be a small circular cylinder with at least one "vaccuum line" and an electrical lead) attached high on the firewall on the passenger side of the engine compartment. Disconnecting several of these, one at a time, during a problem period did nothing to assuage the coldness.
So, unless one of you has a better idea, is there a way I can replace the valve with a manual valve? Even if I have to get out of the car, open the hood and adjust the valve to my needs, it would be a better, cheaper solution than the $300 that a new valve costs. This should work even if the problem is actually some computer chip that commands the valve. And that's about as much money as I want to put in this car with 172k. I'll probably sell it this Spring.
But I'd like to hear of your comments first. Thanks in advance for any help!
12-27-01, 10:45 AM
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I had a similar situation with an Oldsmobile I had. The fan would blow, but there was no heat. I began to notice that it would blow hot air when I was at wide open throttle so I thought it was some kind of vacuum problem. One really cold day I was determined to do something about it, raised the hood and put a clamp on the vacuum line that was connected to the heater core valve. The heater worked great.
Trying the wide open throttle test would at least thell you if you should pursue a solution based on denying vacuum to the heater valve. However, if you need to bypass the valve, you could remove it and get a water fitting that would match the threads and the hose diameter.
I'm not sure what that wire does, but while you're there you might as well try disconnecting it.
Trying the wide open throttle test would at least thell you if you should pursue a solution based on denying vacuum to the heater valve. However, if you need to bypass the valve, you could remove it and get a water fitting that would match the threads and the hose diameter.
I'm not sure what that wire does, but while you're there you might as well try disconnecting it.
11-15-05, 07:16 AM
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Wide open throttle did nothing to my wife's car last night, so I don't think it's a vacuum problem. Does anyone have a picture or exact location and description of where the heater control valve is located on a 1993 SC400?
Chris
Chris
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