Temp Gauge sender resistance? 190E 1985

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Dave Strieter - 18 Feb 2005 03:55 GMT

Does anyone know a couple reference points for the resistance of the
sender for the engine temperature gauge used in a 1985 190E? (For
example, x ohms at 40 degrees C and y ohms at 100 degrees C.) I'm trying
to figure out if the gauge is bad or the sender is bad. The engine is
at normal temperature as measured by a thermometer in the coolant, but
the gauge is reading way low.

Thanks in advance.

Dave

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Richard Sexton - 18 Feb 2005 06:02 GMT

>Does anyone know a couple reference points for the resistance of the
>sender for the engine temperature gauge used in a 1985 190E? (For
>example, x ohms at 40 degrees C and y ohms at 100 degrees C.) I'm trying
>to figure out if the gauge is bad or the sender is bad. The engine is
>at normal temperature as measured by a thermometer in the coolant, but
>the gauge is reading way low.

It's the sender. It's always the sender. How is the wire going to
the sender? Typically because of the vibration they work-harden,
crack get oil in there and all sorts of nastiness ensues. First
thing I'd do is strip off the last 1/2" of wire and make a good clean
soldered connection tothe connedctor then try it.

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Dave Strieter - 19 Feb 2005 17:02 GMT

Thanks Richard. I'll try the wire next. Hopefully it's not the gauge.

I was expecting it was the sender, but if I unplug the wire from the
sender, the gauge reads minimum. Then if I then ground the wire that was
pulled off the sender, the gauge only reads about 40 degrees C. That
sounds to me like it's most likely the wire or gauge. Come to think of
it, occasionally the gauge bounces around wildly, so maybe it's a break
or bad connection in the wire, hopefully near the sender where I can get
at it.

Dave

>>Does anyone know a couple reference points for the resistance of the
>>sender for the engine temperature gauge used in a 1985 190E? (For
[quoted text clipped - 8 lines]
> thing I'd do is strip off the last 1/2" of wire and make a good clean
> soldered connection tothe connedctor then try it.

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Martin Joseph - 19 Feb 2005 19:18 GMT

> Thanks Richard. I'll try the wire next. Hopefully it's not the gauge.
>
[quoted text clipped - 5 lines]
> it's a break or bad connection in the wire, hopefully near the sender
> where I can get at it.

That test certainly rules out the sender as the culprit...

If you have access to the rear of the gauge you can try running another
wire to ground from the gauge and see if that drives it all the way up
as it should...

If that works, then replacing the wire to the sender is a good solution.
Marty

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Richard Sexton - 20 Feb 2005 01:28 GMT

>sounds to me like it's most likely the wire or gauge. Come to think of
>it, occasionally the gauge bounces around wildly, so maybe it's a break
>or bad connection in the wire, hopefully near the sender where I can get
>at it.

Yup, classic sign. Both my temperature and oil pressure gauges did this
and in both casaes it was the wire's connection to the sender (really
easy to fix on a 126)

http://electric.articles.mbz.org/126connectors/

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