Constant Power Circuits

[davery]

I have a power leak somewhere in my 85 that I am trying to trace. It looks like there are 3 always on circuits; M, N and B. Here is what I have been able to determine.
Circuit M – Fuel Injection
Stop Light Switch
Turn Signal Switch
Hazard Switch
Seatbelt Timer
Trunk Opener Switch
Circuit N - Ignition Switch
Clock
Heater Fan Switch
Windshield Wiper/Washer Switch
Lambda Sensor Switch
Radio
Circuit B – Ignition Switch
Cigarette Lighter
Trunk Opener Relay

Does this sound right? It looks like the leak in one of these circuits.

[Hootch]

Looks like we're having similar afternoons. My turn signals/brake lights/back-up lights are wonky, and I'm trying to chase that down.

Mine's a 78, but it looks like circuit 'L' is the one that's always on. Far left, 25 amp, controlling the lighter, clock, courtesy light, hazard warning flasher and indicator, inspection lamp receptacle, remove key, fasten belt, and radio aerial motor.

Good luck!

[davery]

Looks like we're having similar afternoons. My turn signals/brake lights/back-up lights are wonky, and I'm trying to chase that down.

Mine's a 78, but it looks like circuit 'L' is the one that's always on. Far left, 25 amp, controlling the lighter, clock, courtesy light, hazard warning flasher and indicator, inspection lamp receptacle, remove key, fasten belt, and radio aerial motor.

Good luck!

I think my leak is one of these circuits. There appears to be no draw from any of the other circuits with the power off. I'm a little confused about fuse N. It appears from my wiring diagrams the heater fan and windshield wipers are on this always on circuit, but of course they do not work without the ignition turned on. My plan is to remove a fuse and let the car sit a couple of days. If it starts then the leak is not on that circuit.

As far as your rear lights, don't forget the grounds. I was having similar issues and it was the ground on a tail light circuit board. I rewired the grounds on the board and everything works.

[kmoses]

Check the power draw at the electric radio antenna if it retracts when the ignition switch is turned off. Some units will not "shut off" properly when it retracts and continue to draw power.

[davery]

Check the power draw at the electric radio antenna if it retracts when the ignition switch is turned off. Some units will not "shut off" properly when it retracts and continue to draw power.

I don't have an electric antenna, as i don't have an antenna because I don't have a radio. Which may be the issue. I removed the aftermarket radio last year, when I removed the dash, and did not install another. There was a mess of wires for the aftermarket radio and I did not remove them. t is possible there is a short in this mess of wires.

[baltobernie]

Maybe Jimmy Hoffa has the reading lamp on?

The easy way to determine which circuit is drawing power unnecessarily is to use a VOM ($10 H/F one is OK). Pull each of the fuses sequentially, and place the leads of the meter across the two fuse pins. You should see a few milliamps for the circuit running the clock, but none elsewhere. Once you have isolated the offending circuit, it's a matter of finding the specific fault.

[davery]

Maybe Jimmy Hoffa has the reading lamp on?

The easy way to determine which circuit is drawing power unnecessarily is to use a VOM ($10 H/F one is OK). Pull each of the fuses sequentially, and place the leads of the meter across the two fuse pins. You should see a few milliamps for the circuit running the clock, but none elsewhere. Once you have isolated the offending circuit, it's a matter of finding the specific fault.

That is how I determined it was one of those three fuses. They were all drawing current. I think I have it isolated to Fuse N. I removed it for a few days and the car fired right up. This would not have happened before. Now I just need to find the short in these items.

[ekstrandt]

I would suspect that o2 sensor switch. It gave my car blown fuse randomly. Disconnected mine.

[davery]

I would suspect that o2 sensor switch. It gave my car blown fuse randomly. Disconnected mine.

It is possible, it is on fuse N. I will try that first. I also suspect the radio wiring. It had an aftermarket radio when I bought it. When I removed the dash the wiring looked like a rat's nest. I could not seem to determine what all these thin, little wires were for and was afraid to remove them. I bundled them all together and stuck them back under the dash. I should have spent the time and just removed the wires.