Paul, just sent you a PM

Was the fan running and the clutch pulled in?

2 watts isn't going to get that copper block too hot.

Mark: When you pulled the power for the fan assembly you're running on the rear condenser, where did you tap the power from?

I'm pulling power for the condenser mounted fans from the engine fuse block #3 which is for the rear window defroster that I don't use because it no work.

Like this.....ignore comments below diagram as it has been rewired (properly) per recommendation from mystertrain.

Anyway, I'm off to the dealership this AM to see what they can find.

Thanks all for your ideas and suggestions ( and to you electrical experts - thanks for your patience with me)

Will follow-up with what they find.


http://forums.pelicanparts.com/uploa...1180350400.jpg

Problem Resolved: System had been overcharged causing the compressor to run at higher pressure & draw more amperage.

All electricals checked out OK. Dealer tech evacuated the system and then recharged with the proper amount of R-12.

He states that it is normal for the fuse block to get "warm" when the A/C is running full tilt, but it should not get "hot". Static pressure in system before he started was 80psi.

Thanks again for all your help!

"Problem Resolved: System had been overcharged causing the compressor to run at higher pressure & draw more amperage."

??

The compressor clutch is an on/off device, it's current draw isn't modulated by compressor load or pressure. There is nothing electrical in the mechanical part of the compressor beyond the clutch. If there is too much load the clutch may merely slip which will make frictional heat which can heat up the clutch coil but this will increase resistance and cause current to decrease. Clutch slipping can also be caused by an incorrectly set magnetic gap.

Compressor was running continuously or too long (with clutch slipping insufficient compression was occuring) and thereby heating the circuit too long or all the time. Correcting the refrigerant charge level likely solved the slipping problem but perhaps other problems remain:

Running voltage is too high (car's voltage regulator failing?) and this causes excess current draw for fixed resistance items like the compressor clutch coil.

Clutch coil has a internal damage (shorting) and resistance is too low causing it to draw excessive current.

Clutch magnetic gap is excessive (or amp-turns in coil reduced due to shorting causing less magnetic field to be produced) thereby preventing sufficient clamping to occur causing the clutch to slip under high load.

Jim, .....my layman's interpretation.......thanks for the clarification!

:confused: :confused:

Someone better explain this to me

How can this statement from page3 be true?

"1) Disconnected power to A/C clutch and ran evap blower motor only -still heats up"

In my case it turned out to be a bad voltage regulator. I had the same melting fuse problem, but after a replacing the regulator and having the alternator rebuilt I have been running the AC constantly for over 2 weeks. Temps are up to 105http://www.pelicanparts.com/support/smileys/vuur.gif . No more melting fuses.

No more problems here after getting the system evacuated and recharged with the correct amount of R-12 at the dealership! Good thing.....humid 95 degrees yesterday!:)

"system recharged with R12 at the dealership" ?????

Mark...
Do you mean R134? The only place to get R12 is on the black market. Its as rare as King Tuts treasure!!!!! Since it was a dealership (Ellis, Hennessey) it had to be R134.

My 1973.5T has factory AC and years ago and I recall the AC fuse being as hot as hell, but never to a point of melting. Rather then putting in a new fuse block I installed an inline fuse and it has been working great since. I also replaced the older relay in the smugglers box with an updated unit. New barrier hoses, R134 and a fan switch and it runs cold in this Atlanta heat.

Glad to hear your worries are over, BUT if by chance you did find a way to get R12, please let us know your source!!

Bob
73.5T Sepia of course :cool:

Bob, definitely R-12. Shouldn't be too hard to find - just pricey. Wendt's shop did the overcharge (1 can R-12) and Jim Ellis did the evac and recharge with R-12....since I had too much in the system, I guess they came out ahead on product. Han's over at ******** has also got it.....he worked on my system last year and we went through two full charges before getting me back on the road "leak free".

BTW, Wendt charged $45.00 for 1 12 oz can. My father-in-law just gave me a couple of cans that he bought years ago at Kmart for $0.98 each! My how times have changed!

.....well shiver me timbers.......!!!!

I had Bob Sanderson a few years ago (before Peter took the shop) charge me up with R12 at great expense only to see the stuff run out the bottom low pressure hose that night. After replacing all the hoses with new barrier hose (Auto Cool in Smryna) and a new drier, I decided that R134 will have to suffice based on the R12 prices. So far it has been adequate for these hot temperatures, but Porsche AC systems have never been known to be really cold; just enough to keep the sweat to a minimum on sweltering days!

Glad to hear Mark that all is well on your AC now. Very informative thread.

Bob
73.5T Sepia :cool:

Is that what happened here ?

http://forums.pelicanparts.com/porsche-cars-sale/815756-fs-1982-911sc-5000-a.html
quote: It ran fine before the air conditioner condenser fan shorted out and caught fire.