NoSub Dan

So it's finally getting cold even here in Florida. I jump into my trusty 964 and fire up the heater and...nothing. Defrost...nothing. The A/C runs just fine until I try to turn the temperature dial up and the fan stops blowing. I've checked the fuses and they're all okay so what's up with that? One more thing, if the defrost or heat is in the "on" position with the car off, as soon as you turn the key the fan blows hard for about 2 seconds and shuts off. Any ideas?

Rocket Rob

Check the electric heater blower motor in the engine compartment. My car did that same thing and it was traced down to a worn heater blower motor. Replaced it and everything was good as new.

Vandit

If the rear blower isn't functioning properly, the car's HVAC system will only work at max cold and max heat. Anything in between will be shutdown.

boxsey911

Just to be sure, when you say you have checked all the fuses, did you check the 30 amp fuse in the engine bay fuse panel?

NoSub Dan

I don't know about that one. I didn't even know there were fuses there. I'll check that if I can. I must admit I'm not the most mechanical person but I've done things on this car that I wouldn't have attempted with my previous cars. Any help with how to test that fuse (or how to find it) would be much appreciated!!

boxsey911

It's the in the triangular plastic box on the left side of the engine bay. Three 10 mm screw heads to undo to remove the cover - they should only be finger tight but you might need a spanner to loosen them. Then look for the 30 amp fuse in a row of three. You might even find that it still has the original 25 amp fuse which Porsche later decided to uprate to 30 amps. It's common for it to blow - especially if still using a 25 amp one.

NoSub Dan

Thanks for the info. So I got back there and checked all 3 fuses and they're okay. While I'm back there I just check all the connections and bang on the blower a bit and when I checked, I had fan!...but still no heat. I got the fan to operate but there's still no heat. Limited success.

Vandit

Does your car have an aftermarket headers/exhaust manifolds that deleted the heat exchangers? Are there orange hoses connecting the heat exchangers to the flapper boxes in the rear wheelwells?

If all that stuff is in-line back there and the fan runs, then the problem may be the servos controlling the mixing flaps at the HVAC unit that's behind the dash.

Read through here.
http://www.porschehvac.bergvill.com/

NoSub Dan

Flapper Box? Sounds like the roaring '20's female anatomy. Seriously zoomed past my abilities with your analysis but I can say everything looks stock. I'll do more reading on your suggestions though. You had me at Flapper Box.

Vandit

Look through the spokes of the rear wheels, right below the unibody, in-line w/ the rear axle. There should be ducts there. Those are the flapper boxes. They should be connected to the heat exchangers below via orange flexible hoses. These boxes dump out hot air into the wheel well when the heat is off and they route hot air to the cabin when the heat is on.

NoSub Dan

Blower motor. 1000.00 bucks. Thanks for all the input. I learned a lot.

ThomasC2

If any error codes has kicked in due to a bad fuse, relay or something else the CCU will act like this. If so you need a diagnos tool to clear the codes from the CCU's memory. A porsche specialist/center can help hou with this at the codes will also tell you what the problem is. Mich easier than trying to figure it out yoursellf.

And CCU = climat control unit

Kuchar

Maybe, rear blower is just disconected ...
So, disconect temp sensor, and blower should start running.
If wont start, check blower plug connection, then use multimeter to check if there is voltage.

Kuchar

In my car, rear blower realey was faild.
For checking i use same relay from a/c and it helps.

crg53

You are looking at the a/c fans, they are out of this world expensive. What you may need is the blower motor that lives in the engine compartment, Pelican parts have them for under $200.00
Click HERE