Blowing Fuses

[Guest DaveB]

Hi Joel

 

Sounds like you are going around in circuits here I support fully the suggestions made by Daveg it sounds to me that you have a wire shorting to the chassis somewhere, following the following steps should localise the fault for you.

 

1/ Disconnect the battery completely.

2/ Reconnect all circuits and make certain everything is in the off position.

3/ Remove the offending fuse hopefully for the last time.

4/ Connect a multimeter ( set to resistance) between the fuse load side and chassis ( black lead to battery)

5/ Check reading should be infinity.

6/ Switch on each circuit in turn and check the reading (current draw is calculated by

( Current = 12 Volts / Resistance Reading i.e. 12/.8 = 15 Amps or bang)

any reading below 1 ohm is likely to blow your fuse.

7/

[Guest DaveB]

Whoops I slipped on the keyboard try agian

Hi Joel

 

Sounds like you are going around in circuits here I support fully the suggestions made by Daveg it sounds to me that you have a wire shorting to the chassis somewhere, following the following steps should localise the fault for you.

 

1/ Disconnect the battery completely.

2/ Reconnect all circuits and make certain everything is in the off position.

3/ Remove the offending fuse hopefully for the last time.

4/ Connect a multimeter ( set to resistance) between the fuse load side and chassis ( black lead to battery)

5/ Check reading should be infinity.

6/ Switch on each circuit in turn and check the reading (current draw is calculated by

( Current = 12 Volts / Resistance Reading i.e. 12/.8 = 15 Amps or bang)

any reading below 1 ohm is likely to blow your fuse.

7/ Once you have found the offending circuit you need to disconnect wire by wire to narrow it down to one wire and fault found.

 

I would check areas where wires pass through the chassis wiggle them about and get someone to watch the meter at the same time.

 

Good Luck

 

DaveB

 

P.S. Don't be fooled by the suggestion that a dimmer will reduce the current all these guys do is add resistance to the circuit current drain stays the same or more due to losses.

[Joel]

At last! some progress The sidelights are now working without blowing the fuse.

 

If I'd disamntled much more of the car I would have been back to a bare chassis.

 

Ok, so don't laugh but it was the heater blower switch. I just had 2 wires touching that clearly shouldn't have been.

 

This probably seems obvious to all you brainy electrical types, but it was the very last thing I could think of checking:

 

A: because the heater was working fine, and

 

B: because what the hell has the heater got to do with the lights!?

 

The bad news is that only the sidelights are working and I now have no dim/dip etc.

 

Could I have fried a relay and if so, how do you test them?

 

I really appreciate all the help on this one. Most things you can generally work out with enough time and patience, but I've really been banging my head against the wall with this one.

[Longboarder]

The link between the blower switch and fuse 7 is probably the illumination bulb in the switch and it must have been shorting to earth. The blower motor gets its power feed from fuse 18. You could have dislodged the wires when you were making the changes. I still don't get why that would blow fuse 7 only when the headlights were switched on except they both earth through common earth point S1021 to G1005 as does dim/dip relay 34. Perhaps if you check and clean up all the earth points to ensure good contacts all will be well.

 

Very useful, not!. Can't help you fix it but tell you how you might have done it when you've sorted it under your own steam!!

 

Nigel

[Joel]

WooHoo - all sorted

 

Checked all the relays (thanks for the email Steve), no problems there. Scratching head time again. Thought I'd try the new column switch from the scrappy - Bingo!

 

Not sure exactly what the problem was. The replacement column switch was from a newer Sierra, possibly a CVH or DOHC, and was a slightly different design. It has two tags on top, where my original had only one. I earthed the extra tag and hey presto, everything sparked into life.

 

So possibly an earth problem in the old column switch? Either way it works and that's all I care about at the moment.

 

Thanks again to all who contributed.

[Guest Bernie]

I believe that some column switches get their earth through the bottom screw on the right hand switch, there should be an eyelet fitted which is designated as terminal 31 on the wiring diagrams. Some times it is enough just to put that screw in but better to run an earth wire to a ring terminal under the screw.