Temperature and fuel gauge affecting each other

[paul mc]

Hi,

After re-wiring my 1987 3.5V8 Efi i can not get an accurate reading out of the temperature gauge as it seems to be affected by the fuel gauge, i.e. when one goes up the other goes up, at least that's what it looks like.

The fuel gauge appears to be OK as when the tank is nearly empty the reading shows low and the reserve light comes on, but occasionally it does seem to go up and down a bit.

The temperature gauge seems to start ok, reading cold and then slowly going to the mid point, it also creeps up and down a bit for no obviuos reason (i.e. I'm not going up hills or anything like that).

I know I can just fit an aftermarker water temp gauge but i would rather the dash one reads correctly.

What do you think is going on? Is there a shared earth or live somewhere?

Thanks,

Paul

[SteveRK]

Dashboard gauges should be fed via a 9V or similar regulator to allow for fluctuating battery voltages. If the supply is less than 9V then expect gauges to drop. If there is a problem with earthing its likely to be at the sender unit end of the loom although even crappy earths wont have much of an effect as the current draw is so low for gauges.

[discomikey]

with a v8, as the temp goes up the fuel will go down at a similartr pace anyway

seriously though, the regulator may have gone west

[taurion]

Mine does the same when it wants and has done for about the last 2 years, its a 1987 2.4 VM lhd. I assume it is something like the voltage regulator on the back of the instruments wanting to die slowly. So far it has always come back to read correctly ! I always zero the trip meter with a full tank and have a 2nd temp gauge for the day when it dies. In addition my instruments are temperature sensitive. If the interior is below about 5°C no fuel gauge , no temp, and no rev counter, after about 10 mins when some heat has got around the dash all comes to life. Sorry to be of no help but you are not alone with the problem!