islaTurbine

I’ve been reading various threads about this issue but it seems like the majority pertain to later 928 models.

My A/C condenser fan never seems to operate. Ever. I’ve seen it try to spin once but it didn’t make more than one or two slow rotations before it stopped again.

The A/C blows cold on the car unless the car is hot, the outside air is hot, and I’m driving at low speeds. In this single circumstance it seems that the refrigerant charge is loosing cooling capacity because the electric fan isn’t engaging.

Please give me some one guidance on what I can do besides the following:

1. Check the fuses in the CE panel
2. Clean the terminal contacts on the switch on the receiver drier
3. Clean the contacts on the radiator temp switch
4. Jumper the wires from the pressure switch together to see if the fan will operate

Anything else? Also, if I jumper the receiver drier switch and the fan doesn’t work, couldn’t it mean that the radiator temp switch is actually faulty and not the receiver drier switch?

Thanks all.

j.kenzie@sbcglobal.net

Apply power directly to the fan, and see how well it performs. If it runs well, try jumpering each of the switches in line to activate the fan by its normal route. You could always add a relay to turn the fan on whenever the a/c is turned on. If the fan does not run well, there are very good aftermarket units available.
Good luck,
Dave

linderpat

I recall a similar issue with my fan many years ago. It turns out someone had the plugs reversed at the connection. Try unplugging the wires and reattaching in the opposite manner, then test. It's the two shown in the photo.

The Forgotten On

There are 2 switches. One is located on the bottom right of the radiator (when facing the car) This one activates that fan when the coolant reaches a certain temp set by the selected switch.

They're about $20 ( part # 823959481F) and used in all kinds of cars so you can get all kinds of temperature settings. This one almost always has failed. Just replace it to be sure it is working.

The other is the one that has 2 female spade connectors coming out of it screwed into the top of the elbow on the receiver drier. This one doesn't go bad nearly as often as the other.

This one is triggered by the ac refrigerant temp getting hot.

islaTurbine

Probably a dumb question, but how do I get power straight to the fan?

I will definitely try this. Sometimes the best fix also happens to be the easiest.

Thank you. Any thoughts on how much coolant loss is sustained when replacing the radiator switch? I guess it depends on how quickly I can pop the old one out and the new one in?

Christopher Zach

Whoops wrong answer

j.kenzie@sbcglobal.net

Hi isla,
If you look at the condenser fan, you will see an electrical connector coming off of it. Disconnect it, and apply 12 volts to the two pins or sockets on the fan connector. See if the fan spins, or just barely moves. If it spins real fast, then it's OK and you need to trace the chain of connectivity.
Good luck,
Dave

islaTurbine

Follow up question: Does replacing the thermostatic temp switch on the receiver drier open up the A/C system? Basically, will I have to recharge the system if I replace that switch?

giddyupp

Im also following along on this one. My ac fan only comes on once the radiator temp starts getting too high, so im assuming that switch is working ok. I jumped the switch on the a/c drier and the fan came on right away. Though im not sure if this means it is bad. Is this a low pressure switch or a temp switch ?

Christopher Zach

That was the one I was going to answer. No, removing the dryer switch does not open the system; the end of the switch is against the metal of the dryer, not the actual AC fluid.

islaTurbine

islaTurbine

Update:
Pasha sits on top of my 4 post lift above my 911, which just so happens to have the battery in the front trunk making for easy access of 12V power. So I disconnected the 911’s battery and hooked long 14 gauge wires to each post. I removed the lower center grill and disconnected the condenser fan connector. I had a buddy hold the wires in place on the 911 and I touched the positive to the red lead and negative to the brown lead on the fan connector. The condenser fan immediately started turning.

So now I’ve narrowed it down to either the coolant temp switch or the receiver drier temp switch.

Question for the group: if I jumper the two wires on the receiver drier temp switch, will the fan engage even though the cold radiator coolant isn’t triggering the coolant temp switch? I assume the answer is yes but I figured I’d ask first.

j.kenzie@sbcglobal.net

Good. the temp and pressure switches are binary. They are either open or closed, on or off. I believe that each closes when they get hot/high pressure, and sends a ground signal to the fan relay. You should now be able to jumper one or both to get the fan running. I believe the condenser fan will always run with ignition on when both sensors are jumpered. That is not terrible, if your alternator can handle it, it's actually kind of good. If jumpering does not work, look at the fan relay and fuse. I don't remember numbers for your model.
Good luck,
Dave

islaTurbine

The upper switch that’s accessible from the engine bay is a temp switch. The pressure switch on the receiver dryer is lower down and only accessible from the center grill area.

Id think the radiator temp switch is likely your culprit.

islaTurbine

One more inquiry for those here smarter than I (i.e. everyone).

I have the "Porsche 928 78/79/80 Models, Dimensions, Tolerances" booklet that contains a diagram of the CE panel for the 78/79 (and one for the 80 as well). It states that Fuse 16 is for the "Condenser Blower for A/C". It also states that Relay XVIII is the "Extra Fan for A/C". Adding to my confusion is the page at 928Intl for early 928's (http://www.928intl.com/repair/Relay/earlyrelay.htm). It also uses different terminology between the fuse and relay: "A/C Condenser Fan" versus "A/C Fan Relay".

Do both the fuse and relay control the electric cooling fan on the condenser? Or are these two distinct items?