Water temperature sensor question

[Minibobo]

Hi all,
I need your help. We have a customer car with center speedo conversion.
Temp gauge shows irritating temp.
We tried 3 different water temperature sensor with varying elektrical resistance (ohm) but whatevee we try the temp is showing quite high level(3/4), while ir-gauge says just 72degrees.
Has somebody an idea which sensor could give a better match/ show lower lecel?
Or any idea about which electrical resistance it should have?
Any help welcome.
Thx
Bobo

[dklawson]

Temperature gauge sending unit issues are a fairly common problem. You may not be able to find a combination of sender and gauge that will work.

Start with the following observation. Does the FUEL gauge also appear to be reading incorrectly?
If BOTH the fuel gauge and temp gauge are reading high, look for problems with the voltage stabilizer which supplies electricity to the fuel and temp gauges.

If the fuel gauge is working properly (not reading too high) then the temp gauge problem is likely a mismatch to the sending unit. There are two fixes I know of.
1) Re-calibrate the gauge to match the sender. That is easier said than done and there is very little documentation for the process.
See the link below for how to calibrate the fuel gauge. The temp gauge process will be VERY similar but you will have to map out the sending unit resistance change with temperature before you start.
http://www.chicagolandmgclub.com/techti ... e_cal.html

2) Since it sounds like you are asking for a service shop and time is money, suggest to your customer that they add a gauge matching device such as the Gauge Wizard by Spiyda Design. You will have to tweak the settings on the Wizard to get the gauge and sender to match but it should be quicker and more flexible than other solutions. Link to Gauge Wizard below.
https://www.spiyda.com/fuel-gauge-wizard-mk3.html

[Minibobo]

Thx Doug,
We will try....

[dklawson]

Since this car has a dash conversion there is always the possibility that some wiring mistakes were made.

The person who made the conversion may have omitted a good ground connection at the stabilizer or they may have run the wrong wires to the wrong terminals on the voltage stabilizer.
1) On the post-1964 center speedos there is typically a bracket on the top, back of the gauge to which the stabilizer is attached. That provides the ground. If the installer did not mount the stabilizer there... just run a black ground wire to the mounting tab of the stabilizer.
2) Confirm the wiring between the voltage stabilizer and gauges is correct.
Look carefully at the stabilizer's circuit board for the letters "I" and "B" ("B" for battery power in, "I" for nominal average 10V out to the instruments). The "B" terminal should have a dark green wire on it coming from the fuse box. It is a switched, fused, 12V source. Sometimes a second wire is on the "B" terminal. If present, that second wire goes to something like a fan but it does NOT go to a gauge. On the stabilizer's "I" terminal should be two (2) light green wires. One light green wire goes to the fuel gauge, the other to the temperature gauge.

Please let us know what you find.

[Minibobo]

Will check this week and let you know. Thx a lot for the info!

[Minibobo]

Hi gents, issue is solved.
A bit strange but everything is fine now.
Whatever we did, which sender we used and which gauge we tried, temp on display was 20degree higher than in real.
Cable was ok.
Gauge was ok.
Sender was ok.
Offset was there.
So we tried the power stabilizer and chamged-
Still 20 degree too high.
Then we tried without, and temp on gauge became even higher.
So it was clear there is too much voltage.
We reduced the voltage and now the gauge is set up to a 100 percent match to the real temp.
Job done.

[dklawson]

We reduced the voltage and now the gauge is set up to a 100 percent match to the real temp.
Job done.

How did you lower the voltage? The stabilizer's job is to reduce the voltage to a nominal, average 10V.

[Minibobo]

Doug, we put a resistor in the cable. Works really perfect.

[Spider]

Sorry to read of your troubles there.

It'll be the Sender. None of the sender's I've bought in the past 5 or so years have been right, they all make the gauge read high by about the amount you've seen.

I tried the resistor fix too, and while you can get it to read right at Normal Temps, it's not right elsewhere, but is a simple fix.

You can also get Gauge Matchers, but they are not cheap.

[Minibobo]

We tested it with boiling water and it showed exactly 100degree. So i would say it will work.....

[dklawson]

As Chris said, by adding the resistor the gauge will be accurate at one temperature. That may be good enough.

If your customer complains, remember the Gauge Wizard mentioned earlier.

[Minibobo]

We will see when car is in use.
Thx guys