11-04-2009, 09:02 PM
Join Date: May 2006
Location: Vancouver Canada
Total Cats: 0
Troubleshooting Blown Meter Fuse
I had my meter fuse blow on me the other day, and then when I replaced it, it just blew again in a few seconds. Ultimately I am looking to find out what the resistance across the meter circuit should be without the car on, but here's the full details for those with too much time on their hands:
94M 5speed, link, WBO2 that draws power from a circuit other than the meter one, no other devices added to the circuit I can think of, but the car was purchased from someone who did VERY sketchy work and there may be things I haven't found and fixed yet.
I am away from home for a week doing Ansys training for work, and staying at a hotel in Everett with the car parked outside in the cold. It normally lives in my underground parking, so although it get's wet all the time, it doesn't normally spend the night outside. The second morning I was here when I started the car the meter fuse blew. It was cold over night and there was some frost and a lot of moisture throughout the car.
The head was replaced about a month ago, along with the Mtuned coolant reroute, still using stock coils and CAS on back of exhaust cam.
As I'm at a hotel, I don't have access to the proper schematics or decent electrical tools. I'm going on info from other threads and a garbage $10 analog multimeter from Walmart so consider values I give very approximate.
Things normally on the circuit:
1) instrument cluster - Stock, works fine, no indications of internal shorts
2) Turn signal & back-up lamp circuits - Car has Canadian DRL module, all lights work fine and look dry, turn signals work properly when there is power to the modules
3) Power antenna - Mine killed itself inside and has been grinding gears when commanded to move, but is otherwise silent and stationary, is it actually powered from the meter circuit? There is a fuse and wiring to the batter back by it so I always thought the stereo just worked a relay on the antenna.
4) Power supply to heated O2 sensors - I have a WBO2 powered from a different circuit, and I don't believe there is even a NBO2 still on the car.
5) Air bag system - The bags, controller, and some of the sensors are in my parents basement somewhere.... I did a fairly complete airbagectomy.
6) Cruise control - The mechanical parts are gone. Not sure on the control module.
7) Warning system (seat belt indicator) - works as far as I know
8) Auto trans control module, if equipped - N/A
I measured the resistance to ground from the two terminals for the meter fuse, one was about 10 ohms and the other was about 30. Does this make any sense? There is no voltage at the terminals so I would have expected one of them to be essentially infinite?
I disconnected the power antenna, but didn't see any change in resistance. I also dug around looking for shorts behind the coils and CAS and generally all over the wiring but couldn't find anything.
I replaced the fuse, started the car, and everything seems to be fine. All lights, signals, gauges, etc. behave like normal, and the fuse didn't blow, at least for the couple minutes I was running it.
With 10 ohms to ground the circuit should only be drawing 1.5 amps or so, but I assume the drl module and various other things draw more when the car is actually running. Does anyone know roughly how much resistance this circuit should have, or know what the deal is with both terminals having a decent path to ground?
If it doesn't blow again I guess I'll chalk it up to water in somewhere it shouldn't have been, but I'd like to figure out if I have a bigger problem.
Thanks for any help!