Temperature gauge at max when lights or blower turned on.

Hi All,
Very new to Landrover as only owned a 1995 Defender for about a month & in that time I seem to have fixed more things than I did on a boring Peugeot I owned for the previos 4 years, but hey its more interesting.

So my problem is the temperature gauge goes to max whenever side lights, main beam or the heater blower is switched on.(this fault was inherited when I bought it so know it is nothing I have broken during other work) Under normal running gauge reads correctly & engine is at normal temperature.
Do I start checking for a poor earth somewhere, if so where is most likely?
Any guidance appreciated, thanks

I'm not that clued up on electrical stuff but I get by. If it is an earth issue there is an easy one to check, it comes out engine side of the bulkhead near the clutch master, check its present and correct. Not so easy to check is others behind the binnacle, you'll have to pull the clocks to check them.

Flossie said:

I'm not that clued up on electrical stuff but I get by. If it is an earth issue there is an easy one to check, it comes out engine side of the bulkhead near the clutch master, check its present and correct. Not so easy to check is others behind the binnacle, you'll have to pull the clocks to check them.

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Thanks Flossie, I will check these soon, but been thinking that because the system works properly under normal daytime running there cannot be much wrong with the actual circuit.
Maybe I have bare wires somewhere that interfere with the gauge circuit when the lights & /or blower are switched on... would you agree?

If you post your problems in the Defender section you should get responses from more knowledgeable peeps. This is the introduce yourself section.
Bad earths can cause all kinds of weird things to happen so best to check them out first, the temp and fuel gauges work by a variable earth resistance so bad/missing earths might be upsetting the earth circuit to those gauges. If the earth is bad to the blower or lights they will cause issues with other components. We've all seen people's indicators going dim and tail lights flashing at the same time haven't we? That's an earth fault.

Hi Flossie,
Just wanted to say thank you for pointing me in the right direction the other day.
Earth at bulkhead was poor with some rust & paint overspray, sorted that & things improved but not entirely right. Went to Battery earth on gearbox housing to find a rusty buckled oversize washer under the bolt that could never really be called seated & tight, cleaned & changed all of that & problem solved completely. Then remembered previous owner just had a new battery before I bought it, fitted by Halfords. In the battery box was an odd wire that they had cut, traced this back to the bulkhead earth, so somebody had had this trouble before & fitted a seperate earth lead. Reinstated that too just for belt & braces.