No gauges, fuse #18 blow due to a short circuit to ground.
10-20-2017, 10:08 PM
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No gauges, fuse #18 blow due to a short circuit to ground.
Hello all,
I'm a newbie to this forum and looking for some helps with my 1989 Porsche C4 that has the problem with all the gauges not functioning. The problem started when one day I drove the car on first gear at high RPM. I did a lot of troubleshooting myself and also bring the car to the repair shop but still could not resolve the problem. Here are the troubleshooting that has been done to the car: Replaced battery and alternator, checked and verified that the fuse would blow with the alternator disconnect. Following circuit diagrams, found that all gauges, central informer control unit, diagnosis plug and the fuel level sensor all share the same wiring. Disconnected one at a time and found that even with all these systems unplugged, fuse 18 still blow. I noticed that when turn on the key, and check the fuse 18 with meter, one side of the fuse has 12 volts and the other side always short to ground. I could not find where the short and it is very frustrating. I would really appreciate if someone could help me resolve this problem. Thank you in advance!
I'm a newbie to this forum and looking for some helps with my 1989 Porsche C4 that has the problem with all the gauges not functioning. The problem started when one day I drove the car on first gear at high RPM. I did a lot of troubleshooting myself and also bring the car to the repair shop but still could not resolve the problem. Here are the troubleshooting that has been done to the car: Replaced battery and alternator, checked and verified that the fuse would blow with the alternator disconnect. Following circuit diagrams, found that all gauges, central informer control unit, diagnosis plug and the fuel level sensor all share the same wiring. Disconnected one at a time and found that even with all these systems unplugged, fuse 18 still blow. I noticed that when turn on the key, and check the fuse 18 with meter, one side of the fuse has 12 volts and the other side always short to ground. I could not find where the short and it is very frustrating. I would really appreciate if someone could help me resolve this problem. Thank you in advance!
10-21-2017, 03:11 PM
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Fuse#18
If nothing else. Did you replace this part? Note from previous member.
"In previous threads, (see this thread , and this thread) I was having trouble with my '91 C4 blowing the #18 instrument fuse. Eventually, the battery died, and the car would not start or keep running without jumper cables connected.
Today, the car came out of the shop, and the verdict was "bad pressure sender." Part number 964 606 904 00, located on a hydraulic pump housing:
The service guy told me it was probably tied into the circuit for the instruments, and took quite some time for the technician to isolate; four hours, in fact. At $84 per hour. <sigh>. Add that to the new sender and o-ring cost ($214.69), plus towing, taxes, etc., and it added up to a final bill of $663
"In previous threads, (see this thread , and this thread) I was having trouble with my '91 C4 blowing the #18 instrument fuse. Eventually, the battery died, and the car would not start or keep running without jumper cables connected.
Today, the car came out of the shop, and the verdict was "bad pressure sender." Part number 964 606 904 00, located on a hydraulic pump housing:
The service guy told me it was probably tied into the circuit for the instruments, and took quite some time for the technician to isolate; four hours, in fact. At $84 per hour. <sigh>. Add that to the new sender and o-ring cost ($214.69), plus towing, taxes, etc., and it added up to a final bill of $663
10-22-2017, 02:03 AM
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I haven't replace the pressure sender yet but I disconnected the two connectors connect to the pressure sender unit and the fuse still blow out. Therefore, I think the pressure sender is ok but I might replace it when I ran out of idea. Thanks!
10-24-2017, 03:23 PM
#4
Hi,
i had an issue with repeated blowing of that fuse. I had changed out a coil. The metal clip for the ignition coil harness was misplaced and was touching the heat sink behind. Ignition on, gauge would turn on, then immediately blow the fuse. I replaced the fuse a couple times and then the hydraulic pressure switch on the C4 pump got fried, before i went back to ignition coil harness and discovered the problem.
worth a look at the coils to harness connections.
Cheers
FS
i had an issue with repeated blowing of that fuse. I had changed out a coil. The metal clip for the ignition coil harness was misplaced and was touching the heat sink behind. Ignition on, gauge would turn on, then immediately blow the fuse. I replaced the fuse a couple times and then the hydraulic pressure switch on the C4 pump got fried, before i went back to ignition coil harness and discovered the problem.
worth a look at the coils to harness connections.
Cheers
FS
10-25-2017, 01:54 AM
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Thank your for your response! The repair shop found the problem. It was the wiring harness to the belt tension monitor. When the motor mount was installed at the factory, the harness was pinched between the mount and the body. That was a very good find. Thank you very much to Chris and his team!