Temp gauge

[Jasonking]

Hi all, would anyone know if the temperature gauge not functioning, has anything to do with the dynamo/ignition light flickering on at tickover? Also would anyone have a spare gauge just in case?

[Peter Laidler]

I was just going to say that the two wouldn't be connected. But they COULD be connected if yur car was a pre bimetal voltage instrument stabilised car/gauge.

So the next question is, is it an early car/gauge with instant reading gauge or a later car with a slow reading gauge?

[gs.davies]

Just trace the circuit back. It’ll start with a live feed somewhere, go through the gauge and earth out through the sender.

[Polarsilver]

My method with any electrical issues such as this .. get the wireing drawing as seen in a OE Workshop Manual or applicable Haynes Manual ,.. "photocopy" that wireing drawing and then i have a copy that with a Colour Pen or Crayon then trace each wire in with the various cable colour of that gauge panel & you will then see what is going on ( or not) with the Gauge / Stabilizer "earths & power supply.etc ".. then apply the knowledge to your issue, a test light is all that is needed or even use a multimeter if your wealthy .. this method has worked for me for many past decades on various vehicles & equipment ..that was until the Can Bus arrived

[Jasonking]

Not sure if I know what you mean by slow or fast reading gauges? It’s an April 64 mk1 850 super deluxe.

[timmy201]

Not sure if I know what you mean by slow or fast reading gauges? It’s an April 64 mk1 850 super deluxe.

Fast means it jumps straight to the temp when you turn the key

Slow (voltage stabilised) gauges slowly creep to the temp reading

There’s lots of different combinations of gauges, senders, thermostats, voltage inputs

[olddave]

Earth out the wire going to the temperature transmitter. If the gauge goes right up then that's working and probably the transmitter is at fault. Be aware of the different types available as previous comments.

[Jasonking]

Cheers for all your input guys, have earthed transmitter wire but gauge just moves slightly from zero to Cold but no more even when motor is hot?

[roger mcnab]

hi
maybe the gauge and sender are not compatable or just get a capilery gauge you know the one with a long metal tail and temp sensor on the end it would need to be installed in a bracket as it will not fit the speedo housing
cheers roger

[MrNoo]

hi
maybe the gauge and sender are not compatable or just get a capilery gauge you know the one with a long metal tail and temp sensor on the end it would need to be installed in a bracket as it will not fit the speedo housing
cheers roger

Capillary one will fit in the speedo housing, put one on my 8 port and you actually know what temp the engine is (certainly if you buy a decent gauge) far more accurate than an elec in my mind.

[Jasonking]

I’m tending to think the problem may well be the voltage stabiliser unit? If it’s faulty will it also affect the oil pressure gauge?

[Peter Laidler]

If the BMVIS (the bi-metal voltage instrument stabiliser ) is faulty it won;'t affect the oil pressure gauge. That it a direct feed from the block. There is a far better electronic type now but the electronic versions are polarity sensitive. So make sure that you specify + or -ve earth.

If you do get an electronic version, here's what I did using the KISS principle. I disconnected the original one attached to and earthed at the back of the speedo casing. Wired the new BMVIS and pushed it into a 1" length of that grey foam pipe small diameter insulating material. Now out of harms way and vibration proof, it just fits snugly behind the speedo

[BAD942B]

I’m tending to think the problem may well be the voltage stabiliser unit? If it’s faulty will it also affect the oil pressure gauge?

no, the oil pressure gauge is mechanical

[Peter Laidler]

A few years ago I made a very simple, small and inexpensive jig, screwed to a piece of wood, to test all the parts of the BMVIS, fuel and temp sender and gauges. If there's any call for it, I will put a picture up on The Knack.

[Jasonking]

If the voltage stabiliser is kaput, won’t it affect both temp and fuel gauges together? Or are they on separate circuits?

[timmy201]

The sender also needs to have a good earth back to the head/block. Did you use much sealant or thread tape?

Are both gauges stabilised?

[Jasonking]

Only the temp gauge is not working, fuel gauge seems fine, didn’t use sealant on transmitter just cpl of threads of ptfe tape.thanks

[gs.davies]

Remove the ptfe and then see if it’s working. The sender completes the circuit to ground, the resistance being variable based on the temperature. Try shorting the wire to the sender straight to ground and then have a look at your gauge. If the gauge is working it’ll go all way to high (providing you’ve priced out the voltage stabiliser if fitted).

[Jasonking]

Took speedo binnacle off to check gauges, now have lost clock illumination lights! Aaaaaarrrrrgggghhhh!!

[AndyPen]

April 64 should be pre stabiliser type, and the speedo should have a blanked off light position top middle with a 'jewel' in the middle at the top as you look at the speedo face. If you have that correct speedo??? Here's my Feb 64 S one which has the darkened jewel at the top. On the later speedo the stabiliser sits here and there is no jewel / light fitting.

speedo jewel position.jpeg