Aux Fan and AC question
02-17-2009, 07:00 PM
#16
Chronic Tool Dropper
Lifetime Rennlist
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Lifetime Rennlist
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When someone reports that they have cold AC but it goes away when the engine warms up, I immediately think of the heater valve. Either the valve is leaking or the valve is open. In either of these situations, the coolant through the heater warms up as the engine warms up, effectively negating the work of the AC system. Coolant is cold when engine is cold, so AC airflow is plenty cool then.
There are several good diagnostic write-ups about the vacuum system flaps and actuators. You'll need to borrow or buy a simple Miti-Vac tool to perform the testing. They are cheap at Harbor Freight, more expensive but available more commonly at Sears stores. I suspect that you'll discover a vacuum leak at a diaphragm or two, enough leakage to keep the system from closing the heater control valve all the way when it should be closed. The valve is located under the air cleaner housing, hose runs from the back of the pass side head (assumes left-hand-drive US car...) to the valve, then another hose routes coolant across the rear of the motor to the heater connections. The valve is normally open, closes when the engine is running and no heat is requested. You can watch the valve move, tell right away if it doesn't move. You can fudge the fix for a while by wire-tying the valve in the closed position, and see if the problem goes away. If you have a leak in the vacuum system though, your center comb flap is blocking most of the airflow out the center vent, and your dash vents will probably be blowing air up onto the windshield.
Too often we jump at the most complex and expensive and hard-to-diagnose problems, when there's really a simple problem. Star off with the simple stuff when you can.
There are several good diagnostic write-ups about the vacuum system flaps and actuators. You'll need to borrow or buy a simple Miti-Vac tool to perform the testing. They are cheap at Harbor Freight, more expensive but available more commonly at Sears stores. I suspect that you'll discover a vacuum leak at a diaphragm or two, enough leakage to keep the system from closing the heater control valve all the way when it should be closed. The valve is located under the air cleaner housing, hose runs from the back of the pass side head (assumes left-hand-drive US car...) to the valve, then another hose routes coolant across the rear of the motor to the heater connections. The valve is normally open, closes when the engine is running and no heat is requested. You can watch the valve move, tell right away if it doesn't move. You can fudge the fix for a while by wire-tying the valve in the closed position, and see if the problem goes away. If you have a leak in the vacuum system though, your center comb flap is blocking most of the airflow out the center vent, and your dash vents will probably be blowing air up onto the windshield.
Too often we jump at the most complex and expensive and hard-to-diagnose problems, when there's really a simple problem. Star off with the simple stuff when you can.
02-17-2009, 07:18 PM
#17
Racer
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Location: Denver, CO
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thanks,
Trust me guys I've been down tthe vacuum checklist all the way to the orings in my
throttle body.. It's fixed. All the flaps and acutators are working too.
The heater valve isn't the culprit either.
https://rennlist.com/forums/928-foru...re-switch.html
This is going to require the gauges to diagnose this anyfurther.
Trust me guys I've been down tthe vacuum checklist all the way to the orings in my
throttle body.. It's fixed. All the flaps and acutators are working too.
The heater valve isn't the culprit either.
https://rennlist.com/forums/928-foru...re-switch.html
This is going to require the gauges to diagnose this anyfurther.
02-17-2009, 07:18 PM
#18
Racer
Thread Starter
Join Date: Jul 2006
Location: Denver, CO
Posts: 343
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Received 0 Likes
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thanks,
Trust me guys I've been down tthe vacuum checklist all the way to the orings in my
throttle body.. It's fixed. All the flaps and acutators are working too.
The heater valve isn't the culprit either.
https://rennlist.com/forums/928-foru...re-switch.html
This is going to require the gauges to diagnose this any further.
Trust me guys I've been down tthe vacuum checklist all the way to the orings in my
throttle body.. It's fixed. All the flaps and acutators are working too.
The heater valve isn't the culprit either.
https://rennlist.com/forums/928-foru...re-switch.html
This is going to require the gauges to diagnose this any further.
