rrt898

I have a 1986 coupe with a BIG battery draw. I disconnected the ground and placed a test light between the cable and the battery. It lit up like Yankee Stadium. I then disconnect the aftermarket stereo system and pulled one fuse at a time from the fuse box. Even after pulling the fuses, the light is the same.

Is there any common places that cause this?? Anyone have this or similar problem??

thanks for any help.....

oldalaskaman

I may be wrong, but I dont think it works that way, you need a multimeter, and you need to measure the draw across the battery poles. then if you pull the fuse of something thats not shutting off or is grounded when it shouldnt be ,you wiil see it

AGENT 86

Your test is a fail. You need a meter set to amps with the probes in the correct sockets, to measure current draw.

http://www.youtube.com/watch?v=yFCT-YZbU5o

rrt898

I purchased a meter today but; I have no idea what I am looking for. I watched youtube videos and read many threads. Everyone is different.

navy_vette

If everything is closed and all lights are off, you should see less than 0.1 amp. In a perfect world, you'll show 0 amp draw.

Just remember, put the multimeter between the positive pole and the positive cable. If you put it on the 2 battery posts, you will blow your multimeter up. I'm serious. Smoke, possibly flames, the whole 9 yards.

rrt898

So I put the meter on 10 amp setting?? Then attach the meter between the cable and the battery post. What would be a high draw in amps???

thanks again

AGENT 86

Yes, one probe on cable, one on post.

Anything more than 1 amp, I would consider a large draw. Be sure your courtesy lights are out when measuring.

rrt898

OK....I attached the meter....It was reading 0.87 with everything off. I saw an inline fuse just below the battery. I pulled out the 30amp fuse and the reading dropped to 0.02. I guess this is my draw. I traced the wire to my main fan. Then back to the two relays near the battery. If I tapped the relay the drain would drop to normal. I went and bought two new relays. The reading is now 0.02 with the fuse back inline. I hope this is the problem. I will see tomorrow if the battery is dead.

thanks again for the help.......

jfb

You found the problem, congratulations. GM says leakage current should not exceed 50 milliamps. My 87 draws 27 ma and I have never had a problem with the battery discharging.

rrt898

jfb.....I know this sounds stupid but; how do I measure milliamps or whats the conversion of 0.02 amps to milliamps??

thanks...

ccrazor

1 amp = 1000 milliamps. .02 amps is 20 ma.. LOL

jfb

yep.

rrt898

After I replaced the two relays I still have my draw. I know its the 30amp inline fuse that gives the one relay power, that controls the man fan. Does anyone know if that relay needs constant power?? I could just power the relay from a key switch source.

thanks again.....

jfb

I own an 87 and I believe the 86 wiring is very close to mine and I do not have a 30 amp in line fuse anywhere. I believe that fuse was installed and the coolant fan uses a fusible link. Something else is on that circuit that is drawing excessive leakage current and you need to find it. Do you have any aftermarket electronics? GPS, CB, radar detector, audio amp, radio, anti theft? Disconnect them and see if the drain drops.

rrt898

I know the fuse doesn't belong. I am sure the fusable link blew and somebody installed the inline fuse instead of replacing the link. The inline fuse powers the relay to the main fan. My question is does that relay need constant power or can it be powered up with a key source?

thanks.

jfb

Yes the 30 amp fuse goes to the coolant fan relay contact and needs to be connected to 12v all the time. The fusible link did the same thing and the only circuit it supplied power to was the coolant fan. BTW, the coolant fan motor draws 24 amps. You must have something else connected to the 30 amp fuse drawing current because open relay contacts have such high insulation resistance that home milliammeters cannot measure the leakage current due to its extremely small value.

rrt898

The inline fuse only powers the relay to the main fan. I don't know why there is a 30amp fuse inline but; why would the relay need constant power?? Is the fan supposed to run when the car is off??

jfb

The fan does not run with the ignition off. The fan relay is a switch that turns on the fan and with the ign off, there is no way for 12v to get to the relay coil. The ignition switch cannot handle an additional 24 amps to the fan relay. Besides it doesn't make sense to connect two switches in series, the ign sw AND the fan relay.

rrt898

So then my main fan is the draw. Is the main fan's motor burning out?? The relays are new and tested. If that relay is only powering the main fan, what else could it be?

thanks

jfb

The fan motor is not defective in my opinion because with the ignition off the fan relay cannot close and apply 12v to the fan motor. The fan motor is not connected in any way to the battery with the ign off. There must be something going on at the relay sockets. You might try tapping on the new relays while watching the leakage current. On my 87, the insulation on the wires going to the two relays on the firewall are gone and I have bare wires on each socket. Fortunately I haven't had any problems with shorts. Look carefully at the wires on the relay sockets and see if a previous owner tapped into a wire to get 12v for some accessory.