temperature gauge trobles

[Mat Norris]

Can anyone help?...... I have a problem with my smiths water temp gauge fitted to my xflow. If I switch the headlights on, the temp needle starts to rise from a normal reading of 90-100 degrees to an alarming 125 degs. When the lights are swit ched off, the needle falls again. This seams very strange to me because I would think the gauges would under read when the alternator was loaded more??? Also the gauge tends to creep up very slowly on motorway journeys to the 125 degs but if I switch the lights on and off again the temp needle will fall back to a normal reading. I'm pretty sure the engine is not overheating as the thermoststically controlled radiator fan seems to come on at normal times and is not on when the gauge has crept up to 125 degs.

Could a dodgy connection or something cause this?? Or is there a link between the headlights and the temp gauge electrical supply connections. The gauge only creeps up and down with the lights, other elecrical bits like the heater have no effect.

Thanks for any help you may be able to give.

 

Mat

[Simos]

Just a thought. Check your alternator belt (and alternator), if it is tight enough that it generates enough power to run everything except when the lights are on you'd see something similar. Reason being the fan is a big drain, might come on when the lights are off but doesn't run if they're on. I had a similar experience when my alternator died. The faster i went the hotter it got. It'd have to be a hot day though as cool weather driving shouldn't need the fan.

 

Cheers, Simon.

[Roger King]

This is outside my area of expertise, but I have seen similar problems before and they have usually been caused by a faulty earth under the dashboard.

 

I believe that there is a point where the loom earths to the chassis under the scuttle on the passenger side. Sometimes this becomes unreliable due to loose connection or even the chassis powder coat getting in the way.

 

Worth checking anyway.

[Mat Norris]

Thanks, I shall check both things out and cross my fingers!

[CHRIS CLARK]

I too would think that this is an 'earth' problem.Certainly this would my first line of attack.

[JampJ]

If your using smiths gauges for your fuel and temp,the live(batt)feed to the gauges must be via a voltage regulator,this supplies a fixed steady voltage,stopping any fluctuation in needle movement due to any changes in voltage.I would also check the earth connection between the engine and the chassis as this can cause countless strange electical problems.1 REGULATOR will supply both gauges, available off most minis using SMITHS gauges.Also available from GOWER OAKS

mail order.0800 731 2456(very helpful).

good luck.C7 POW

[JampJ]

Just thought i'd mention,the only earth connections to the gauges are via the temp sender unit on the cylinder head,and via the petrol sender unit in the tank.The actual gauges dont use any earth connections,apart

from the intrnal light.Both gauges should be wired to one regulator.If it's only the temp gauge that's fluctuating maybe it's not wired to a regulator,then you will get strange readings.I'm on 0161 681 8015 or 0860233252 daytime,if your stuck give me a call.NO WORRIES

C7 POW

[JampJ]

Just remembered,the voltage regulator must be earthed,usually by it's body being screwed to the body.

CHEERS

C7 POW

[John E]

I had this problem at Le Mans except that in addition to the lights having an effect on the temp reading there was also a problem with the wipers. It was the earth that Roger refers to. Mr Rat Race pointed me in its direction and I was surprised that it had ever worked because the bracket is powder coated. Some rubbing with an emery board, didnt have any emery paper, sorted the problem big style. Before you ask I borrowed the emery board from a fellow camper!!!

[Roger King]

John E.

 

When you obtained your emery board at Le mans, who was the camper, - you or him?

 

Best Wishes,

 

Roger