I know it's a long way to summer, but the low air conditioner switch on the dash of my 95 C2 993 lights when pushed but nothing else fires up---no fan, no air. The high switch works. Any thoughts on where to start in trying to figure out what's wrong.

 

fuse or relay

 

Hi Tom,

I'm not real knowledgeable with respect to the A/C system, but like freeman, I'm thinking of a relay or perhaps an interlock. A couple of thoughts ....

Does your interior fan operate normally when not running the A/C? Or, does turning on the (normal) A/C button kill the interior fan?

This shouldn't stop your A/C from operating, but does your condenser fan run when you turn on the A/C? If you don't know already, the condenser fan (or blower) is in the left front fender. You should be able to hear it running with the A/C button pushed (ignition on).

There is a "final stage" controller for your left and right blower motors (I believe this is what gives you the infinite speed control). Perhaps it is only outputting a "valid" signal for the high-speed? Thus, my question of whether or not your interior fan operates normally when not running the A/C.

 

Tom,

The A/C, heating system in the 993 is a very complex system that is driven by a computer system separate from the engine DME unit, the easiest way to tell what is wrong with the unit is to hook the "Hammer", Tester 9288 to it.

With the error code read out on the tester you can find out exactly what's wrong with it.

Robin

 

Thanks for the ideas on the air conditioningbug. I will check fuse and relay...any idea where and which?
The interior fan operation does not seem related to the air conditioning. There is NO fan sound when the low speed air cond. button is pushed though the switch light does come on. Thanks for the ideas, Randall.
Robin, I will probably have to resort to the "Hammer". Thanks for the above help and info.

 

I had problems getting the fan to run a few months ago. Turned out I was futzing around in the fuse panel to install a cell phone and must have unseated a few relays. I reseated all of the relays and all is fine.

Curtis

 

Hi Tom,

The compressor relay and fuse is in the rear fuse box. However, I haven't been able to imagine a way that your relay & fuse could be bad, and yet your A/C works with the MAX button.

Now, the following is a plausible explanation, and why I asked if your interior fan works normally with the heat:

-If the rear (heater) blower motor fuse is faulty, it will cause the interior fan to cut-out when temperature is set above (I believe it is) 21C. This corresponds to when the rear-blower motor will normally start and begin supplying hot air.

-Now, assume your rear blower motor fuse is faulty. Let's also assume you have the temperature set above 21C.

-Considering what we assumed above, the interior fan will not run.

-You hit the "MAX Cool" button, which automatically sets the temperature to the coolest setting. Now your interior fan will run, and you get A/C.

That's all I can think of for now ... best of luck!

 

While we’re on the subject of A/C problems…

This is not a big deal, but I’ve noticed that I get substantially more airflow through the air ducts on the drivers’ side, as compared to the passengers’ side. Has anyone else noticed this? Is it by design? I’ve pretty much decided not to worry about this, but if there’s an easy fix…

 

Hi Tom,

I have also noticed this--in particular, with respect to the vents in the middle of the dash. With both vents fully open, the driver's side vent gets much more air than the passenger's side vent. To equalize the flow, I have to throttle down on the driver's side vent. This not only decreases the flow on the driver's side vent, it also increases the flow on the passenger's side vent.

To be honest, I don't know/remember if this is normal. The good thing is it's just a matter of adjusting the vent to get equalized flow.

 

Thanks for the confirmation, Randall, especially the part about my decision not to worry about it! I was just worried that one of the internal valves that directs the air (you know, dash versus feet versus windshield) was sticking…

Tom