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First Post! Dodgy Temperature Gauge?


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Hi All, i'm new to the site. I'm running a Defender 90 200tdi with bout 213,000 on the clock. After a major overhaul of lots of new stuff, steering box, alternator, starter motor, pwr steering pump, wheel bearings, head gasket to mention just some of the stuff! It's nearly right now though apart from a few niggly things that need doing (I HOPE).

The problem I have is with the temperature gauge which when I do long distance at about 65 - 75 mph it bounces about mainly in the red hot area of the gauge, sometimes literally bending the needle off the end.

It has only done this once or twice locally when the engine is just warm not hot. But every time I drive for over an hour it happens and mainly at high ish speed. Then all of a sudden it will go back to normal.

If when this happens and its in the red I pull over and turn the engine off then back on again it goes back to normal and sits just a needles width above half way.

I have replaced the sender which fixes into the top of the engine and it hasnt made a difference.

Any advice would be greatly appreciated as it gets a bit scary at times and generally ruins my outing.

Thanks Terra Dog

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you need a cross head [philips] screwdriver,

scroll to page 771, remove screws item 11 & 14 from each end of the instrument pack panel, ease it forward, enough to get your hand in to squeeze the clip on the speedo cable to release it from speedo head, then you should be able to see the small circular nuts securing the black earth wires to the back of each gauge, just ensure these are as tight as you can do with finger pressure, reconnect the speedo cable & relocate the instrument panel & it's 4 screws.

if that doesn't work, your probably needing a new gauge.

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before condemning the guage it could be a wiring fault...

If the sender wire were to short to ground, it would read maximum, and the jitteryness might be for instance a chafed thru wire vibrating against a piece of bodywork.

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OK i'll have a look at the weekend at both the opinions given. I must get it sorted though because it's doin my head in.

I would just like to add, what an awsome site, i can't believe it's got answered so quickly and in so much detail.

Cheers Guys

Also, will I be able to pull the sensor wire through the bulk head grommet in order to check for any breaks in the wires plastic coating? Or is it part of a loom?

I will check that the earth connections are tight first though cause it sounds easier.

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OK i'll have a look at the weekend at both the opinions given. I must get it sorted though because it's doin my head in.

I would just like to add, what an awsome site, i can't believe it's got answered so quickly and in so much detail.

Cheers Guys

Also, will I be able to pull the sensor wire through the bulk head grommet in order to check for any breaks in the wires plastic coating? Or is it part of a loom?

I will check that the earth connections are tight first though cause it sounds easier.

you can sse part of the temp sender wiring at the engine end & at the bulkhead mutlipin plug, then it goes into the main dash area loom & reappers at the gauge wiring.

the wire may be brittle at the engine due to heat & age, it can be replaced by a 'jumper' wire from the sender to the mutliplug or gauge.

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Aftermarket gauges vary in quality massively, I wouldn't trust anything I read on a Halfords one but VDO Vision are quite lovely. Then again, you already have a temperature gauge which tells you what the people who made your car thought was important.

I vote for sticking thermostat - take it out, test it (boil in a pan of water), check it's genuine and has a jiggle-pin bypass. I had a couple of non-genuine ones which would stick or airlock, the engine would boil before the thing opened, then settle down and behave itself until the next start from cold.

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I had a similar issue with my Temp gauge and it annoyed the heck out of me.

Every time I was in a hurry or towing a boat then quickly the temp gauge went into the red.

I keep my Landy in perfect mechanical condition and knew it was not overheating in reality.

Latter I noticed turning on the headlights the temp gauge would rise slightly.

Anyway, after putting in a new wire from the firewall to the gauge earth,, all was fixed.

Phil....

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I just re-built my engine loom as heat/oil/age had got the better of it, after fully removing it I found verious cracks in all the wires, where the wire insulation had totally perished, could have easily earthed itself to the block...

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I've just checked the U bracket on the back of the gauge and it was loose. So i've tightened it up now and hopefully this should cure the problem, what do you think?

If it does'nt then I will have to check somethin else.

Thanks for the replies and the help.

Terra Dog

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I've just checked the U bracket on the back of the gauge and it was loose. So i've tightened it up now and hopefully this should cure the problem, what do you think?

If it does'nt then I will have to check somethin else.

Thanks for the replies and the help.

Terra Dog

was there a balck wire with a ring terminal fitting under the nut, if yes & the nut is now tight, that should cure the problem.

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