Porsche 911 SC AC problems

[hdrockerroller]

My AC works great with the fan speed set to 1 or 2.
But if I turn it to 3, the evaporator fan and condenser fan go dead and the compressor disengauges.
I'm thinking maybe the switch itself is bad, but does anyone else know anything that can cause this symptom.

Paul

[targa80]

This is the schematic for the A/C in 82 SC, It seems that the third position is effecting the 12volts being supplied through fuse 20 (25 amps.) Fuse 20 supplies the power for the A/C clutch, front condenser cooling fan and the three position evaporator fan. If you understand how to use a multimeter I would recommend doing a continuity test without power to check for a short to ground in the A/C fan switch and evaporator fan resistor unit.

[hdrockerroller]

Yes, thank you. good info.

I've been going over the wiring diagram in the Bently book, I'll have to pull apart the console to get at the wires to get the volt meter on them. The switch is over 30 years old, so it wouldn't surprise me if its gone bad. I don't see much else in this circuit that could really cause this symptom other than the switch, since high by passes the resistor pack completely. Figure I might as well replace it if I'm going to have it all apart anyway, but then why pay for something you don't need too, so I'll test it first. I just wish pelican had free overnight shipping , I hate waiting on parts.
Paul

[wwest]

Originally Posted by hdrockerroller

Yes, thank you. good info.

I've been going over the wiring diagram in the Bently book, I'll have to pull apart the console to get at the wires to get the volt meter on them. The switch is over 30 years old, so it wouldn't surprise me if its gone bad. I don't see much else in this circuit that could really cause this symptom other than the switch, since high by passes the resistor pack completely. Figure I might as well replace it if I'm going to have it all apart anyway, but then why pay for something you don't need too, so I'll test it first. I just wish pelican had free overnight shipping , I hate waiting on parts.
Paul

Check the fuse 20 FUSE/HOLDER..

EXAMPLE: Yellow fuse holder is TU! To much heat over the long term. Replace with an inline fuse/holder.

[Algernon]

Originally Posted by wwest

Check the fuse 20 FUSE/HOLDER..

EXAMPLE: Yellow fuse holder is TU! To much heat over the long term. Replace with an inline fuse/holder.

What is "TU"?

[wwest]

Originally Posted by Algernon

What is "TU"?

Breasts UP!

[hdrockerroller]

I've checked voltage at fuse 20 and it appears good on both sides.
I'll recheck the voltage at the fuse with fan on high, but according to Bently fuse 20 is always hot.

[hdrockerroller]

Oh and of course also checked fuse 20 holder, looks ok.

[hdrockerroller]

Ok, I bought the replacement switch from our host.
Part #911-613-243-00-M100, and the shaft is too small.
The shaft has one flat side that is supposed to fit against the flat spot in the hole in the console. Is there some kindof retro filt for this part, do I need an adapter, or di they just send the wrong part. (I've never received a wrong part from pelican ever before).

The old nut won't fit, the shaft just turns in the hole. Also the wiring looks slightly different and switch did not come with any info.

Anyone else replaced their blower switch with the one from pelican before?

[targa80]

Originally Posted by hdrockerroller

Ok, I bought the replacement switch from our host.
Part #911-613-243-00-M100, and the shaft is too small.
The shaft has one flat side that is supposed to fit against the flat spot in the hole in the console. Is there some kindof retro filt for this part, do I need an adapter, or di they just send the wrong part. (I've never received a wrong part from pelican ever before).

The old nut won't fit, the shaft just turns in the hole. Also the wiring looks slightly different and switch did not come with any info.

Anyone else replaced their blower switch with the one from pelican before?

I don't have an answer to your question on the short shaft of the switch, but I am curious did it cure the electrical problem of killing the A/C in position 3 ???

[hdrockerroller]

The shaft isn't too short, its the wrong diameter. Too small around.
I haven't tried it yet in case I need to return it.
I'm trying to find out if this is the new part update, or just the wrong part.

[hdrockerroller]

So the problem did turn out to be the switch.
The new switch has a slight fitment issue and you need to order the nut for it and just tighten it down real good. You also have to get out the bentley and an ohm meter and figure out which pins of the new switch get what wires (it is different from original switch). But when all was said and done that was the issue, have good working fan in all positions now.