firemn131

Hey all. Car is running great!!! except.....
After removing some of the extra wiring and bypass switch that the PO added..i have a fan issue.. When the thermo fan switch comes on at 92 degrees the fans start and immediately blow the 16A fuse #3 . The PO had this fuse bypassed and used a rocker switch in its place.
I tested the fans individually...Both work as advertised individually. When i have them connected individually they come on and cycle as they should. When both are connected they blow the fuse. I was looking at a later wiring diagram and they have a 25 amp fuse..

Any suggestions. I did a resistance check on both of them and they are the same. which suggests that the on first glance they are ok.
My next test i think is gonna be to try and find out what the initial start up amperage is per each one. The fuse box and all grounds and terminals have been meticulously cleaned in the last 2 months.

Has anyone experienced this before? Also, has anyone upped the fuse rating?

thnx

John

klm2500hd

My fuses were blowing last summer, everything checked out good, even amp draw. Was pulling 7 amps and still blowing fuses. Replaced fuses with different brand and haven't had one blow since.

firemn131

K. I will try that..
How did you test for the amp draw?

thnx

cruise98

Check the wiring at the resistors for a short.

firemn131

Ok...So.i couldn't find the resistors....i ran the fans in all modes..individually, together, and with the harnesses swapped...
All results are at high speed...(AC on)
both fans read from 6.4 to 8.0 amps individually...
Together the ran at 11.amps..
I believe these are within normal limits.
the fuse is 16..
But when they are first turned on they spike..Now most electric motor circuits are rated at 120% of load to account for the huge draw from starting from a standstill.

But here are my start loads.

Individually 11 to 12 amps.

Together...it was spiking to a momentary 25 Amps..

It was getting to the point that it was melting the fuse...

So, any suggestions..Do i just need to take the motors apart and clean the rotors and bearings up?
Or, can i safety run with 1.

On this circuit there is also the headlight pop up motors, and the blower fan for the heat..It has a draw of 9-12 amps..i don't member what the surge rate was.

I didnt get the chance to run the fans from the 92 degree switch and the heater blower...

So give me your feedback..haha

thnx

StoogeMoe

I looked in the wiring diagrams and for the 83 they have fuse 3 as 16 amps. But in the wiring diagrams for USA with Air conditioner they have fuse 3 as 25 amps.

I checked my car, and there is a 25 amp fuse in there.

The later cars have 25 amp fuses for each fan.

The headlight motor and heater blower motor are not on this circuit. They have their own fuses. Only the cooling fan is on fuse 3.

Yarf

Is your car a 1987 924?
Looking at the prints it appears that each fan should have a separate fuse, if I am reading the print correctly
fuse 5 and fuse 3.
Fuse 5 Coolant Fan Motor
Fuse 3 Condenser Blower

firemn131

well, it looks like i need to dig a bit deeper..I thought that i seemed odd to have so many motor accessories on one circuit.
I will take the fuse panel..and seats out again. And see if the fans have separate feed at the fuse panel. if not then i will pull that circuit of and see if i can assign a separate one to it..Thanks for all the help. I have heard that the wrong diagrams for this MY are hosed up,

Yarf

Porsche info can be found here.
http://www.texasblake.com/porsche/docs.html

Good luck
Keith

firemn131

So, Fuse 3 is 16 amp and fuse 5 is 25 amp.
Oh and it is an 87 924S

I took fan readings again..
fan 1 draws 8.5 amps,
fan 2 draws 7.5..

Fuse 3..if it goes it takes both fans and heater blower and pop up headlight motor...
Fuse 5..when it goes it is because of fan 2...

So, without good diagrams i am assuming that 3 also controls the relay that runs the motors,
I am wondering if the PO put the other accessories back on the wrong fuse...or if all of the relays for them come from the #3 fuse.

Could the wiring actually be correct but the fan relay going bad?..

at this point i think the fans are fine...
but i have got to find why this #3 keeps blowing...If i let them run and a 25 amp in the #3 slot it actually melts the fuse before it blows...

Yarf

Good diagrams can be found here:
http://www.texasblake.com/porsche/docs.html

Nicebento

Hey firemn131, Where you able to figure the issue out? I am having the exact same issue with my 83 944. I've been trying everything but I have had no luck...