David Crooky

Hi all looking for some help in readings with ohms.

i have been having problems with my 15amp engine fuse blowing completely ramdomly. I have looked for shorts and can't find anything. I tested from each **** with the fuse out with ohms set on 20k and am getting a reading of 0.05. I want to know if this is to much resistance and causing the fuse to blow. Thanks

David Crooky

Its a 1986 rx7 fc

scotty305

iTrader: (2)

A working fuse should have a resistance of less than 1 ohm... the exact value may be different for different fuses, and when measuring such a low resistance the wires of your multimeter also start to influence the measurement. If you measure more than 1 or 2 ohms resistance across the fuse I would swap it for a new one. If you have blown multiple fuses, that indicates there is a problem somewhere on the car, unless you're using a fuse that is the wrong rating for that circuit.

Don't switch to a higher-amps fuse, that could result in burnt wires and electrical fire. It's not uncommon to have intermittent wiring problems in older cars, especially if they have been modified or if the wiring harness has been moved around during other maintenance work. Try to find a pattern in when the fuses have blown in the past... was it at high RPM? Was it while driving on a bumpy road? Was it when certain devices turned on? Find the wiring diagram in the factory service manual, and track down which things get powered by that engine fuse. Look extra closely at those parts of the harness, maybe unwrap the loom and check for broken or chafed wires before you re-wrap it. Electrical problems can be tricky to find, good luck.

David Crooky

Thanks for your response. It tends to blow at high rpm or when i hit a bump. I think im going to unwrap the harnness and replace all the wiring running off the fuse

peejay

The easiest way to check for what is blowing a fuse from a probably chafed wire is to replace the fuse with a light bulb and start manipulating the wiring harness. When the light glows bright, it's shorting out and you know where to dig deeper.

A couple male spade terminals, 8-10 feet of wire, and an old turn signal bulb/socket wil make you your own non-fuse short finder tester rig.