Morris Minor Owners Club

Hello, I am fitting a temperature gauge to my car. I have connected it as the wiring diagram shows in the technical tips. This is the second gauge I have tried and doesn't seem to be reading any thing on the gauge. I put multi metre on and that shows 10 volts at the sender in the engine and 10 volts at both connections on the gauge. Could this be a problem with the sender. As I said this is the second gauge and both go up if connected to a battery charger and work fine. The problem lies when I connect it up any help will be grateful. many thanks

One side of the gauge should be at 0V , you have probably got a bad earth .

Andrew

should I put on earth of the gauge?

I put on earth of the gauge and still nothing?

There are different designs of gauge, so the wiring can vary. Generally speaking there will be a +ve supply to the gauge, and the earth return is accomplished through the sender (-ve earth car, situation reversed for +ve earth). When it is cold, the resistance is high and little (if any) current flows. As the sender gets warmer, resistance drops, more current flows, and the gauge goes up. Most gauges start reading only at 40 degrees C, and so won't read anything when first turned on with the engine cold. There usually also be a wire for illuminating the gauge, connected to the dash lights.

Electronic or digital gauges tend to have a +ve and -ve connection to the gauge, with a comparison of earth return made through the sender.

With the gauge fully installed, take the wire off the sender and connect it directly to earth. Do you get any reading now?

For info, over the years, I have found that the analogue gauges are far mpre accurate and reliable than the digital ones. That surprised me, but it is backed up by readings with a thermometer.

when I put the connection from the sender to earth the gauge goes to hot and then when disconnected goes back down hope this helps

The gauge is an electronic smith temp gauge

Check you have resistance to earth on the temp sender and it is not a very high resistance don't forget to disconnect the sender first

If the gauge reads hot when you place the sender wire to earth, and back to cold when you take it off then the gauge is working correctly. If it fails to show a reading when the engine is hot then the sender is u/s.

If you need to confirm that, and you have a multimeter, check the resistance between the sender terminal and earth when the engine is cold, and again when it is hot (obviously disconnect the wire that leads back to the gauge for both the tests).

If the two readings are the same or very similar that's confirmation of a kaput sender.

As above - the sender is not doing the job, the gauge is working perfectly - where have you installed the sender??? Further above - a 'digital' gauge - really?? I've never seen one for a Minor, but I dare say they are available. Digital instruments are generally ultra accurate - that's the point - the reading doesn't need any 'interpretation' by the user.

It turns out it is the sender. This was a brand new sender as well. many thanks