Help, I overcharged the A/C and blew the fuse

[rick-l]

Originally Posted by tshih

Well, I've ordered a new relay for the smuggler's box and been bleeding off the freon (or condensing it back into the can by chilling the can down to dry ice temperature (-78 deg C). Next weekend I'll give it another go at tracing the fault that keeps the fan from coming on. The evaporator fan may just be blown during the time the fuse got tripped and the cabin vents gave off the acrid odor and smoke like freon/lubricant
discharge. The current theory for my problem is still overpressure in the system tripping some protective measure that prevents the compressor clutch to engage and the fans to circulate.

There is no way the freon charge influences the electrical current drawn by the compressor clutch or fans to the extent it would blow a fuse.

[tshih]

Another piece of the puzzle: I tried swapping the red round A/C relay in the fuse box with the relay at the other end of the box (position G) and when I went for a drive the circuit (G) which is the fan for aux air booster behind the instrument cluster was powered on all the time even after I shut off the engine. pulling the relay was the way to stop the fan from spinnning. Hence that relay which was the original A/C relay in the fuse box was shorted on when the fuse got blown.

[rick-l]

Originally Posted by tshih

Hence that relay which was the original A/C relay in the fuse box was shorted on when the fuse got blown.

Or the current from the short in the blower or clutch arc welded the contacts together.

[rick-l]

Originally Posted by rick-l

There is no way the freon charge influences the electrical current drawn by the compressor clutch or fans to the extent it would blow a fuse.

Of course I could be wrong answer from a pro (last answer from NickD)

perhaps you should check the coil resistance. What it should be I don't know.

[ruf-porsche]

If you have a front condensor with the fan check to see if the fan turns freely. Over time they become seized and because they are not on a fuse circuit (not unless a PO did the mod and install a fuse, wink, wink) the motor start drawing current until it starts melting the harness. Google or do a search for condensor fan fire Porsche.

Advice from JW on another post about the same subject

Originally Posted by john walker's workshop

jw, it's the front AC fan, down by the battery, that normally burns up. hard to say how to tell when it's going to go. maybe that old burnt plastic smell will give you enough warning.

[tshih]

Well, the new relay came and after installing in the smuggler's box the fuse blew again! I try putting 12V across the two wires of the condenser fan near the battery and did not hear any whirring noise. Checking connectivity resistance across the two wires (brown and yellow/black) showed infinity. Next I looked at the evaporator fan under the smuggler box lid. Removing the square plastic cap (with the wire on top of the box), I felt the fan and it was warm to the touch.

Question: if the evaporator fan is toasted what is involved in replacing the fan portion only and not the evaporator coil underneath the fan?

[tshih]

Well since the evaporator fan isn't necessarily burned and costs over $250 to replace, I took out the motor for the front condenser fan. Sure enough as John Walker said, that motor was burnt (hence the acrid smell coming out the vent) where the brushes made contact with the shaft. The fan cage was hard to turn by hand and only freed up after lubrication. Ordered the replacement motor and should install after june 1st.

[Tigerrat]

So with that fan disconnected will the evap fan run w/o blowing the fuse? Many folks add an in-line fuse to that front cond. fan.

[ruf-porsche]

Originally Posted by tshih

Well since the evaporator fan isn't necessarily burned and costs over $250 to replace, I took out the motor for the front condenser fan. Sure enough as John Walker said, that motor was burnt (hence the acrid smell coming out the vent) where the brushes made contact with the shaft. The fan cage was hard to turn by hand and only freed up after lubrication. Ordered the replacement motor and should install after june 1st.

If you review all the previous posts, J.W. never posted on this thread. J.W. was quoted on this thread.

[tshih]

Tigerrat, I haven't tried running the evaporator fan with the front condenser fan disconnected. I'm not sure if the evap fan will run if the fuse is replaced (ran out of fuses).

I suppose my problem is not related to the overfilling of the freon as some have objected to. Just a coincidental timing for the fuse to blow and the motor to burn.

[T77911S]

i hate to tell you this. you cant tell if the system is full unless it is running, and you have air flow over both condensors.
get a box fan and place it on the rear glass blowing on the rear condensor. make sure the front fan is working. you may even want to put a fan up front, but not too close, just a little extra air flow.
with the AC on hi, doors closed, motor at aound 1500-2k, check pressures.

r134 or r12?

if you let freon out based on 45 psi static, that sounds low, i think it is usually around 60 with it off, but that still does not mean it is full.

you have a site glass on the dryer, check it with the system running, that is actually better than pressures.

porsche does not use a low pressure switch, unless they did on the newer ones.

i have seen the clutch make a car cut off and back on quickly. my volvo is doing it now, i had a jeep that did it and my moms volvo also did it, dont ask me why, but it does. i got so frustrated with mine on a trip, i bypassed the low cut switch, best thing i ever did, the ac blows colder and yes i know why it is there but i dont care.
i hate the ac system in that car and i am tired trying to get it to blow cold.
new compressor, cleaned the evap and condensor, flushed, vacuumed and it still blows in the 60's at best, now it blows 40 with the low cut bypassed.

[tshih]

T77911S, I agree with you, was only trying to diagnose why my fan and A/c system is blowing the fuse and doesn't come on anymore.