1983 SDV Electrical Drain

[George Woodford clc21025]

I have an electrical drain on my battery from an unknown source.  After three to four days without starting the car, the battery is dead and I have to jump it.  I have checked for lamps remaining lite such as engine compartment, truck, doors, map lamps, glove compartment, etc.  All are off.  Any ideas what may be causing this electrical drain?

[Rusty Shepherd CLC 6397]

George, I had the same problem with a later model SDV and it turned out to be the climate control fan running on low even when the ignition was off.  Its been so long ago that I dont remember which component was replaced to fix the problem. Check your floor and dash vents for air movement with your ignition turned off. If you dont feel air movement, listen carefully for the fan motor sound in case the vents are closed even though the motor is running.

[Rusty Shepherd CLC 6397]

On second thought, if your battery ONLY runs down after the car has sat two or three days, its probably not the blower motor as it most likely wouldnt take that long for it to discharge the battery.  When my car was doing that, it would run completely down overnight and be slow to crank after several hours.

[TJ H 20664]

I have a 78 CDV that had a battery drain.  Turned out to be the horn relay.  The horns didnt work when I bought the car so I tried a new relay.  When I first replaced the relay I could hear the relay click but the horns still didnt work so I moved on to other more pressing issues and forgot about it.  To find what the load was coming from I used my multimeter on the 10amp setting connected in series with the - side of the battery.  Not all meters have this option.  You can also use a test light or any other light like a tail light or dome light or something like that.  WHen there is a load the light will glow or light.  You then start removing fuses and or relays till the light goes out then you know which things to look at.  On mine something must have broken in the horn contact in the steering wheel.  Since the horns didnt work anyway I just left the relay out.  I know the 83 had an electronic climate control vs the dial and lever on the 78 so I would hope they upgraded the rest of the design but on earlier cads including the 78 there was a relay that turned on the heater/ac fan.  On my 78 and 3 other 78s I looked at the relay socket and the relay had melted.  It looked to me that it was a margnial design in the relay that caused the contacts to overheat and distort the plastic base of the relay and eventually the socket.  I could imagine as part of this process the relay deforming to the point it was stuck on therefore keeping the fan running all the time.  Eventually it deforms to the point of not working at all.  For some reason 78 seems to be the high point for this problem, maybe they put in a larger heater fan??  I replaced the relay with a modern standard Bosch style HD one and the system has worked great since then.  In a 78 the relay board with the horn and blower relay is next to the fuse block under the drivers side dash between the brake pedal and the kick pannel.  I sold my 83 15 years ago and dont remember having to deal with any electrical problems so I cant tell you where to start looking.

Let me know if you need more info on the test light thing, I can try and explain it better.

Good Luck!

TJ H
20664
StPaul/Mpls MN USA