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Temp gauge and headlights

Argh I hate auto electrics.

My temperature gauge slightly bumps up when i turn on my headlights and gives a slightly more violent bump if I put on high beam. Also, with the headlights on, sometimes (when you're far away from home, so as to give you the biggest fright) the temperature gauge will climb from 1/2 to 3/4 but will go back down to 1/2 if I turn off the headlights, and will sometimes go back down on it's own even if I don't turn off the headlights. I also noticed the rear windscreen heater light on the dash coming on very very dimly when it's off and the rear door is opened and the headlights are on. The headlights work perfectly (no dim, flickering thingies etc) and all other lights also work perfectly and have no effect on the temp gauge.

I'm VEEERY new to auto electrics so I don't know where to look. I haven't had time to check much yet, but I did check the main earth cables from battery to gearbox etc and they're fine. Now that the weekend is approaching I might have more time to tinker around. So is this definitely an earth problem and should I go ahead and rip out the headlights and check/clean the wiring there or is there anywhere else I should look for causes of this?

Btw, don't now if it's related, but I just fitted lamp gaurds, front and rear. However I don't know if the problem was there before or not.

Thanks for any advice

Dennis

Reply to
Dennis
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Most likely guess by remote control from the other side of the world - a dodgy earth connection for the dashboard. A quick check of the wiring diagram should let you trace back to where the dash light circuit is earthed - make sure the connection is clean.

Reply to
EMB

It would help if we knew what sort of vehicle it was, but the most likely problem is either a faulty earth to the gauge itself and the effect is through the instrument light circuit, or there is an actual temperature rise due to slipping fan belt caused by the extra load on the alternator. JD

Reply to
JD

Hi Dennis,

When you say the temp bumps up, do you mean instantly, or does it go up over a few minutes?

If it goes up suddenly, and bearing in mind what you say about the HRW, I would be inclined to check the electrical earth for the instrument panel. Is the fuel guage affected at all ? Does operating the indicators/flashers have any effects.

If it is a slower rise, and particularly whilst driving, it may be that the fan belt is slack, casing slipping of the belt under hgh electrical load. Don't know what vehicle you have, but if the fan belt drives the waterpump too, then its possible that the pump slows down when the belt slips. This scenario is a long shot, but seing as it is a few seconds job to check the tension of the belt it is worth doing first.

Sorry for generic advice, but I don't know what vehicle you have....

Good luck, Tezza

Reply to
terry

Hi all. Thanks for the advice. Sorry for completely forgetting to say what vehicle it is. It's a 1995 Defender 90 TDi300. The gauge needle "bumping" is instant when turning on the lights. Kind of like giving it an electric shock for a fraction of a second then goes back to normal. While driving sometimes it would just freak out and instantly jump to 3/4 hot. From there it would go back to normal either on it's own (instantly back down to normal) or by turning off the lights. I might add that during the day the gauge is always dead on the half way mark no matter how hard I push the engine so I sure there isn't an actual temperature rise.

Other lights don't have effect on this. Fuel gauge works perfectly (thank god). I guess it could be the gauge lighting earth too as that comes on with the headlights. I'll try giving it a go at the weekend. Thanks for all the suggestions :)

Dennis

Reply to
Dennis

Hi all. Thanks for the advice. Sorry for completely forgetting to say what vehicle it is. It's a 1995 Defender 90 TDi300. The gauge needle "bumping" is instant when turning on the lights. Kind of like giving it an electric shock for a fraction of a second then goes back to normal. While driving sometimes it would just freak out and instantly jump to 3/4 hot. From there it would go back to normal either on it's own (instantly back down to normal) or by turning off the lights. I might add that during the day the gauge is always dead on the half way mark no matter how hard I push the engine so I sure there isn't an actual temperature rise.

Other lights don't have effect on this. Fuel gauge works perfectly (thank god). I guess it could be the gauge lighting earth too as that comes on with the headlights. I'll try giving it a go at the weekend. Thanks for all the suggestions :)

Dennis

Reply to
Dennis

On or around 14 Jul 2004 06:28:20 -0700, snipped-for-privacy@di-ve.com (Dennis) enlightened us thusly:

what they said, plus there may be an instrument voltage regulator in there somewhere as well.

Reply to
Austin Shackles

Almost certainly the earth on the gauge. This is a wire joining the attachment screws on the back of the gauge, and my guess is that the nut on the temperature gauge or the one where the earth to all the gauges is, is loose, and all that is required is to tighten it. May also be dirty. There is no separate voltage regulator on this model. JD

Reply to
JD

Thanks JD, I'll rip open the dashboard at the weekend and I'll let you know how it goes :)

Dennis

Reply to
Dennis

If you've not done this before, be VERY careful pulling the instrument pod out from the dash - it's all to easy to break the instrument illumination bulb holders away from the instruments and its a swine of a job to fix them!!

If you plan on removing the steering wheel, (not really necessary but makes the job much easier) may I respectfully suggest you slacken the nut but don't remove it - when you are pulling the wheel away from the s/column it tends to come free with a bit of a bang and can easily end up craking you in the teeth ;-(

Mike

Reply to
Mike Buckley

I wish you'd posted that before... :)

Reply to
David French

Oh dear. Anyway, LOL - as it 'appens, I did!!

formatting link

(Sorry)

Mike.

Reply to
Mike Buckley

Thanks all. Turned out it was the temp gauge earth or something in there. Tightened/cleaned every connection I could find ... hasn't manifested itself again :)

Thanks

Dennis

Reply to
Dennis

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