Blowing fuses

[Menno van Rij]

Things are progressing with my TR; no troubles whatsoever, until now… I put in a new battery and tried and tested the electrical circuit. First of all: the lighting works perfectly, but the part of the electrical circuit that’s controlled by the other fuse (with the four green wires so to speak) is a mess.

I put a temporary light bulb between the spades preventing that I’ll not go bankrupt on fuses. Every time the light starts to glow or lights up, I now that there’s trouble.

 

Nothing seems to work all right, I need help! Let me show you around in my little shop of horrors:

- There’s a current between the fuse and the wiper motor. As soon as I connect the green wire to the wiper motor, the bulb lights up;

- There’s a current between the fuse and the control head. As soon as I pull the switch on top of the control head  to the left or the right, the bulb lights up.

- There’s a current between the fuse and the fuel gauge. As soon as I connect the U bracket at the back of the gauge, the bulb start to glow.

- There’s a current between the fuse and the brake switch, when I floor the brake pedal, the brake lights will not come on (but that can also mean a faulty brake switch).

 

There are 4 green wires connected to the fuse box, all serving the aforementioned parts of the electrical system. Currently I’m running out of ideas and it upsets me… (understatement!)

I’m not sure it all is traceable to one thing, or that there’s a shed load of problems waiting to be solved.

Any ideas, advises or does it sounds familiar? Please respond!  

 

Menno

[jonlar]

Hi Menno, sorry I can't pinpoint a single place for you to check, but to get your symptoms, there's live-side wire or connection that's been connected incorrectly to earth.   As the lighting circuit is OK, it must be related to something off the fuse box.   If you've got a multimeter, disconnect wires one at a time from the fuse box and see which go directly to earth/chassis/body on the resistance range (probably show less than 4 ohms).   Connect one meter probe to a good earthing point and test wires individually with the other probe.    Hope you can follow this and it helps.

[marvmul]

There’s a current between the fuse and the control head. As soon as I pull the switch on top of the control head  to the left or the right, the bulb lights up.

-

Isn't this like it should be?

Did you try disconnecting the wiper motor and put a fuse in place?

Sometimes the parking switch in the wiper motor is faulty : this switch is earthing the motor till the wiper is in parking position. The dashboard switch operates the wipers also by earthing the motor, not by connecting a 'plus' to it.

[Dave Herrod]

If you are temporarily replacing the fuse with a bulb, it would be expected to light every time a circuit protected by the fuse is switched on.  

 

If fuses are continuously blowing, you need to check each circuit separately with a multi meter to find where the problem is.

 

Dave

[Nigel Lay]

Are you sure you have connected the battery polarity the same as the one that you replaced ?  If you have any later additions like radio or something they usually have a protection diode in them that will short if the polarity is wrong.  If  you have - disconnect them, if not and everything was OK before the battery was changed there must be a disturbed wire that has shorted to earth.

Nigel (with TS952)

[Menno van Rij]

A short update. After reading your replies I had another go with the electrics. And with your suggestions I narrowed it down to one culprit: the wiper motor.

 

First of all: Marvmul’s question started to make me rethink the control head left/right blinker problem. And yes off course! He’s right: turning on the left or right light automatically triggers the test lamp. I tested this by pulling off all 4 green wires, disconnecting and connecting them back one by one until I found the right wire for the left/right lamps. With the fuse in place, they work perfectly, with the fuse removed and the test lamp connected, the  test lamp comes on as soon as I move the switch. First of the green wire-problem solved.

 

Then I got on connecting and disconnecting the other green wires. The fuel gauge wire makes the test lamp glow, not shining brightly. I think that the tank sender unit is to blame. Fiddling with the wire near the sender unit makes the lamp to stop glowing. I think that the U bracket was the first 'route' for the current to take to fully close the circle. (Do you know what I mean? I can not find any other words for it in English)

 

The wiper motor is the main source of trouble, I think. As soon as I connect the green wire to the wiper motor, the test lamp lights up. Using a multimeter shows a resistance of 7.6 ohms. A guy from a local company (who specialises in car electrics) told me on the phone that the resistance should be much higher. (Well, I honestly don’t know; I’m not very good with car electrics, as you have already noticed… Any comments on the guy's words?)

 

The brake switch has returned to the hunting fields in the sky. (I should have known, there’s a new one in one of the boxes that came with the car).

 

And off course I followed the advice to check all earth connections. All these seemed to be in good health.

 

For now, thanks for all your helpful advice. By combining all advices, it seems that I’ve found the problem. I’ll keep you posted.

 

Menno