Temp and fuel gauge annoyance

[80s-new-man]

I’ve a new fuel gauge in 2020 that never seemed right on the gauge, reading far too high.
On a recent long journey to beaulieu I noticed the fuel needle went up then down then up again in constant straight traffic. Weird.

I’ve changed the temp sensor a few times now. I’m sick of it always reading so low it hardly gets off the bottom.
I measured voltage at loom and at sensor to block when hot. 4.6 volts at all locations.
I’ve swapped temp sensor again and yes I’ve tried white ringed and a new one from car parts in motion, which they say is a 2.8 version . I’m tired of keep changing them.

I’m just wondering - are these symptoms of fuel and temp behaviours the result of a possible faulty voltage regulator?
If so, can they still be bought?

Help most appreciated!
Cheers

[Mc Tool]

I would be lookin at the reg . I think they are supposed to regulate instrument voltage to a bit over 5v. Dunno if you can still get them new but a 5v dc reg is not that hard to come by .

[nemo]

You need to check the voltage on the lead when it`s disconnected from the sender (temp), If that`s showing about 5v the regulator`s probably OK, it may well be that the connections to the regulator on the PCB need cleaning? Making & breaking due to vibrations while moving?

[80s-new-man]

Ok thanks.. I have just dismantled the dash, soldered on a Capri club replacement voltage regulator and same. Took spade connectors off and on sender, seemed ok, but sometimes no reading at all. Put back in seems ok but just reads full but off the scale. It’s always done that.
I don’t think much of the clubs sender units, having had my mechanic repair the last one as it leaked at the connection points. But I think the readings got worse over the last 3 years. Especially the erratic ones.
The temp annoys me. I will buy yet another white collared version then and see what happens.
Gutted to have taken the dash apart and put it back together only to shear off one of the trims.
If anyone has a spare 2.8 lower dash trim right hand side that goes over the ignition and bonnet latch I would be grateful.
I really appreciate any other causes it could be!

Cheers!

[nemo]

Sorry that hasn`t solved your problem...

Put back in seems ok but just reads full but off the scale. It’s always done that.

That does sound to be almost certainly the sender unit shorting internally, maybe intermittently?
I wouldn`t buy another temp sender, it`s unlikely they`re all faulty. If you have a multimeter, check the resistance at room temperature, then put it in a pan of boiling water and check the resistance dropping as it heats up. (I got ≈32Ω at 84`c for a known working example)
Just to re-check, if you take the lead off the temp sender, what V do you get between the lead and the block? If that`s 5v, ± 5%, and the resistance of the sender with the engine hot is round 30Ω, then it really looks like the gauge itself?

[D366Y]

You mentioned your sheared off the dash trim - which bit do you mean? Just wondering if you had loosened the steering column slightly to let it drop when you are removing/refitting the dash? Gives some extra wiggle room

[Caprigear]

Ok thanks.. I have just dismantled the dash, soldered on a Capri club replacement voltage regulator and same. Took spade connectors off and on sender, seemed ok, but sometimes no reading at all. Put back in seems ok but just reads full but off the scale. It’s always done that.
I don’t think much of the clubs sender units, having had my mechanic repair the last one as it leaked at the connection points. But I think the readings got worse over the last 3 years. Especially the erratic ones.
The temp annoys me. I will buy yet another white collared version then and see what happens.
Gutted to have taken the dash apart and put it back together only to shear off one of the trims.
If anyone has a spare 2.8 lower dash trim right hand side that goes over the ignition and bonnet latch I would be grateful.
I really appreciate any other causes it could be!

Cheers!

I have a later 2.8i dash trim piece, the one with the extra hole for the speaker fader unit.. As for the fuel sender, try replacing the wiring and connectors to the unit itself, making sure that you connect it up properly, if not then the gauge will go right off the scale. I tend to trim off the last 2-3 feet of the wiring to the gauge and replace with new. The white ring temp sender is correct.