Water temp gauge

[mamoose124]

Hi guys, it has been a while since I posted here. After restoring my 1962 Alpine I have spent most of my time enjoying it. It now has over 6,000 miles on the new engine and is running fine. A joy to drive. However, recently the water temp gauge has begun to register at the 190 F mark but the engine is not running hot. The sending unit is new so I’m thinking that the gauge might be the problem. Any suggestions will be appreciated.

 

[hartmandm]

Are you using an infrared thermometer to check the engine temp?
Do you have a series 2 temperature gauge?
I don't think the replacement senders available now provide the same resistance values at the various temperatures as the original senders. Which sender unit did you purchase?

Mike

 

[GlennB]

I'm not sure you can buy the old spec sender's now. My SII engine builder put in a later guage to match the new sender when my original failed. Wrong needle colour of course so might not satisfy the purists.

 

[mamoose124]

Are you using an infrared thermometer to check the engine temp?
Do you have a series 2 temperature gauge?
I don't think the replacement senders available now provide the same resistance values at the various temperatures as the original senders. Which sender unit did you purchase?

Mike

First, the sender and gauge have worked properly through over 5,000 miles since I restored the car and installed the new engine. Normally, the gauge registers just over the 170F mark. If the outside temp is over 70F, the gauge reaches the 180F mark. However recently the gauge started registering just under the 190F mark even on a moderate temperature day. As to the actual temp when the gauge is at the 190F mark, I used a meat thermometer (all I had available) and it registered 150F.I think this temp is probably close to the actual temp as there is no steam coming out of the car and it feels about normal under the hood. I still think it is a gauge problem but am unsure.

 

[alpine_64]

190 is not at boiling point.. so there shouldmt be steam coming from the car.

You should do a process of elimination:

Check the temp sender with an infrared thermometer aimed at it.

verify the ohm of the sender.

make sure the gauge hasn't got a bad ground or slightly loose ground.

 

[mamoose124]

I’m thinking of installing a capillary tube type gauge under the dash as an alternative.

 

[hartmandm]

If it is the gauge, it is easy to swap it out. But I don't think you have determined what is really going on yet. It could also be the sender or something else.

You haven't clarified if you are using a series 2 temperature gauge.

What sender did you purchase? I'd expect you to see some inaccuracy on the gauge even if the sender was working properly, as I'm not aware of any replacement senders matching the OEM series 1&2 sender. But if the sender reliably sends the same resistance at a given temperature, then you can figure out that when the gauge is reading "X", the temperature is really "Y". Then you just keep an eye out for whenever the gauge is reading lower or higher than the expected "X".

If possible, start by testing the sender and recording the resistance you are seeing at various temperatures. That can be compared against the data Tom H gathered when he tested the series 2 temperature gauge. You'll want to use an infrared thermometer to know the temperature, or remove the sender and use a pot of water to test it.

The temperature gauge can be tested, but you would need to use a variable resistor (potentiometer) rated to handle the necessary current.

A test rig I made to test multiple senders for DanR a while ago for his 2.8 V6 efforts:


Mike