Continuous short in '88 VW Jetta

[MaxTheKnife]

This was actually an intermittent problem to start with. But this time it looks like it's here to stay.

A little background on the problem. When I first got this car I noticed something funny with the seatbelt light. There's a bad ground connection on the shoulder harness and the seatbelt light comes and goes as you're driving. That's not a big deal until you turn the turn signal on. Then the seat belt light dims with each flash of the turn signal. Either direction. The heater fan and headlights also cause the seatbelt light to dim. The higher speed on the fan, the dimmer the seatbelt light. Same with the headlights.

The big problem is that if I let the car sit for more than one day the battery will drain down below 10 volts and the solenoid won't even click. And the little fuel pump light on the dash won't go out either. There's a time delay for starting that car. It gives the fuel pump time to pressurize the line I guess. It has a funny type of fuel injection system I'm not familiar with. Anyway, my short term solution was to buy a cheap battery isolator that disconnects the negative terminal by turning a knob. That's a pain because I have to pop the hood every time I park it and know I won't drive it for at least a day. But it was a cheap band-aid at $1.50. I can live with it like it is but I sure would like to find that ground/short.

My problem is I don't know where to start to isolate the grounding/short condition. Everything works in the electrical department besides the rear window defrost grid and the fuse is good. All the lights work, the horn honks etc... So where would you start looking and how would you go about it. I know that finding shorts is a real pain and don't have any practical experience with it besides plain old luck. I'd appreciate any suggestions or helpful hints.

 

[richw]

Max The Knife

Finding automotive short/drain offs is always fun.

The simpilest way I've found is.

1. Go to your local parts store and get a circuit tester (it looks like a pointed screw driver with a light bulb in the handle and 1 wire coming from the back

2. disconnect the positive battery terminal and clamp the aligator clip on the tester to the terminal and then push the pointed end of the tester into the posative battery post. so that it appears the tester is completing the circuit ( you will need an extra set of hands)

3. Make sure that everything that draws power in the car is turned off ( ie: dome light, radio and such)

4. If there is any draw on the battery (ie: battery drain off) the light on the tester will stay lit.

5. Now all you have to due is have someone hold the tester and watch the light. While you pull the fuses one at a time. When you find the offending circuit thats causing your battery drain) the light will go out.

6. Then the fun starts

 

[MaxTheKnife]

Thanks richw, that's a great idea. It sounds like way more fun than I want to have with it right now though. It'll make a real good spring time project.

 

[WFK]

6. Then the fun starts

For my own cars I always buy the repair manuals. They contain the schematics.
Without them I would be lost.
If you have one, a DC Amp meter would be better than a circuit tester. The drain on your battery seems to be significant.

In any case the method given by richw is correct, and in your case you can just put the tester (or meter) across the cutoff switch that you have already installed. (In and Out of the battery is the same current.)