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Rear Fog Light And Speedo Issues


Guest infernii

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Guest infernii

Hi all,

 

My first post!

 

I recently bought my 2B knowing there were some issues to correct before the next MOT, but before I dove under the bonnet, I thought I would ask your advice.

 

1) When I turn on the lights to main beam, everything is perfect but when I turn the rear fog light on at the same time, it blows the LHS main beam fuse. I could just hard line the rear fog to the battery and switch but I would rather sort the problem in the loom if it's a simple fix.

 

2) My speedo is dead. It may just be the cable. Its using the old sierra gauge cluster. Is there any common faults or usual places to check first?

 

Thanks!

 

Dan

 

Jobs still to do:

 

1) fit wet weather gear

2) fit windscreen wipers and motor

3) install demistor

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What size is the fuse that blows? It could be simply an inadequate fuse or it could be that the wire to the rear fog light has worn through someplace and is shorting to ground. You can check for shorts by useing a test light ( old working bulb say indicator 21W with leads to crock clips soldered on ) between the battery +ve and both connections of the rear gog light in turn with everything switched off, if the test bulb lights up for both connections then you have a short in the fog light cable.

As for the speedo then most if not all sierra guages were mechanical and the cable easiest to install cable route involves a sharp bend just out of the gearbox where the inner breaks.

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Guest jelleyhead

Hi i have the same cluster in my super spec i all so had this problem mine was a simple fix as the cable had not been pushed all the way in to the back of the cluster so the cable was just spinning the cable has a square end that goes in to the back of the speedo as you push it in and the outer sleeve you should hear it clip on to the back of the cluster if thats ok it mite not be in at the gear box end or could be snagged some were along the way hope this helps in some way

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Guest infernii

thanks for the speedy replies!

the fuse is a 10 amp which to me seems a little small considering the other headlights run on a 10 amp without the additional draw of a fog light. If it is a short somewhere, i suppose i could test it by putting in a 20 amp fuse. If the wire has shorted then it should still blow, if not then 10 amp is too small of a fuse. I will have a go and post back.

 

i will have a look at the rear of the cluster and hopefully it is just a slipped cable. fingers crossed.

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Guest 2b cruising

If you hard wire the fog you will probably fail next mot.

Supposed to be wired through headlight so cannot be turned on without them.

Latest rules for IVA, it must turn off when headlights turn off, then stay off when lights turned back on, even though you have not turned them off by their own switch.

This is to stop them being left on for the next journey if the fog has gone.

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Headlights at 60 watts only need to draw 5 amps each and a 21 watt fog needs an extra 2 amps making 12 amps, so a 15 amp fuse should do.

 

If your headlights are less wattage, you might get away with a 10 amp one.

 

Watts = Volts x Amps.

 

Don't overdo the rating on the fuse as the next fuse will be the wiring itself which you DON'T want. :)

 

Simon.

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Guest infernii

Just checked. It is a short somewhere in the wiring system. I will hardline it for the MOT and just to be safe I checked the requirements for fog lights on an MOT:

 

This inspection applies to the one rear fog lamp which is required to be fitted to the centre or offside of vehicles first used on or after 1 April 1980.
Note: A rear fog lamp is permitted to operate independently of headlamp, position lamp or ignition systems.

 

So I think I will be ok. The speedo cable was a touch loose so I removed it and refitted it. Fingers crossed that worked. As soon as it decides to stop raining long enough I will take it for a run down the drive and report back.

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Guest infernii

quick update:

 

fog light wired and working!

 

Fiddled with the speedo cable with no luck. I then disconnected the cable and went for a slow drive and I could see the cable spinning so that ruled out the cable or anything at the gearbox end. The car came with a gauge cluster from a 92 sierra so I took the gauge out of that, plugged it in and went for another drive. Hey presto, it works! I havent tested it since i have refitted the new gauge into the old cluster but im sure its solved.

 

thanks for the advice, i am sure i will be in need of more soon.

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