Climate Control

Temporary fix for system stuck on "hot"

Temporary fix for system stuck on "hot"

For those of you still struggling with our Sharks' well documented propensity to turn themselves into blistering saunas, I think I could offer a temporary quick fix, which at least:

1)doesn't require any spare part (maybe...) 2) takes just about 10 minutes of work 3) doesn't require you to tear apart your center console

This of course assumes that the cooling system works (compressor OK, circuit properly charged, etc..)

Whatever the source of your problem is (sensors, control unit, air mix vane control, vacuum leak, or even all of the above), the symptom can be cured temporarily (= until you really have the time to get down to the root cause) by shutting down the supply of hot water to the heater core. (No hot water = no hot air...)

The hot water control valve is located in the engine compartment, between the firewall and the engine, under the air filter, about the centerline of the car

To gain access, remove the air ducts, air filter and the filter housing (need a 10 mm socket). Be careful not to damage the fine grille protecting the air flow meter.

The valve is actuated by a vacuum actuator that open/closes it (looks like a bell). The closed valve position is with the rod pushed inside the actuator. (the rod is marked AUF <---> ZU, auf =open, zu= closed) Disconnect the rod from the valve's lever and close the valve manually, turning the little white nylon lever in the closed position and voila!

While you have access to the actuator, you should test its function. Chances are that with its location in one of the hottest places under the hood, this could very much be the defective component anyways!!

Test is simple:

1) disconnect the vacuum (white) line (and plug it temporarily if you intent to drive without the actuator in place) 2) remove the vacuum actuator by twisting it out of its holder (pretty much like a camera lens!) 3) Push the rod in slowly, you should feel air coming out 4) plug the vacuum connection with a finger, and release the rod If the rod comes back out (ever so slowly...) while your finger still blocks the vacuum connection, you have a leaky actuator...! Bingo! (Well...maybe.. you may have multiple vacuum leaks still...) If you have a vacuum test pump (IMHO every 928 do-it-yourself mechanic should have one!) the test is even simpler and more definitive as you'll be able to accurately monitor the vacuum leak rate. Put the whole thing back together and enjoy another COOL ride!

Granted, you now only have a "on- off" A/C situation, it is still an improvement relative to the heater "on" all the time!

Hope this helps...temporarily

928 Tips Home     Greg's Home