S3 temp sender problems

Hi all,havnt been on here for a while since I got rid of my freelander but last Sunday I took delivery of a 1973 s3 station wagon in need of some tlc and an mot which it is booked in for tomorrow .so this past week I've been going through a list as long as my arm of jobs that needed doing for the mot. But I do have a small problem that's bugging me and that's the temp sender,with the ignition on the gauge would go straight into the red so I disconnected the wire and the needle would come back to the bottom of the gauge,if I earthed the wire it would shoot back to the red as it should do right ?, so I replaced the sender with a new one and now it barely reads at all,any ideas guys?.the
Landy is also fitted with an abro ex milatary petrol lump and I don't know how this differs to the standard but it's bugging me asi need to know what the temperature is doing any info would be great

Did you use ptfe tape when putting the new one in?

No I didn't is that all it could be?

You shouldn't use tape - it will read low.

Are you driving the thing or just letting it idle - it might not be getting very hot, mine doesn't until you actually drive it. one way of testing is to jump lead the sender to chassis and drop it in a cup of boiling water.

Well it's a brand new sender switch and it is only idling although I did take it for a drive today just around the block but I wasn't really concentrating on the gauges to much I was just trying to make it back in one piece , that was some scary ****.ive only gone and bought myself a tractor .but It will have a good run tomorrow to the mot station. Could it be the voltage regulator ?

Voltage regulator does the fuel gauge as well so you would expect issues with both, I would test the sender with the boiling water check as above. Could be a faulty new sender

Well as it happens I think there might be a a problem with the fuel gauge too,when I bought the car it didn't have a drop of fuel in it so I put one green can in and it hardly registered but I thought that was fine,then yesterday it ran out of fuel after working on it all week so i put two green cans in at £15 and I thought that would have made a difference but the needle remained under the red . What's the reserve capacity ? Will another £10 Get the needle up ? Is the sender stuck where it's had no fuel in it for a year?

Sounds like voltage regulator then but first check fuses are not dirty (under steering column)

I just replaced my temp sender. The old one was like yours, it would move up to the bottom mark on the gauge and stay there. I think it was from a different engine or something because the new one I put in looked very slightly different. You'll probably have to go for a quick drive to check it, that's what i had to do to make sure it worked.

Well the landy has past it's test with very little wrong and I've been driving it for the last 2 days and the list of jobs to do is getting longer and I know for sure that the temp & fuel gauge are definitely not working,but there is some movement on both gauges. So I think I need to check all wiring behind the dash and see if the wiring has been altered at all as I have a later petrol engine with an alternator and the landy was originally a diesel I believe, but the last owner assures me that when he parked it up a year ago both gauges we're working so out with the test light again..