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Temp sending unit

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fishinhard

Member
HI all,
1979 GM 250 IL 6. I replaced the Temp sensor due to the old one was not working. Now when I turn on the key, engine is stone cold it reads 120 deg. Do I have the wrong sending unit or is my gauge just not compatible with the sending unit?
At normal temp the gauge is almost pegged out at idle. Inferred thermometer says temp is good right around 110-130
 
The Merc. manual says your engine uses PN 59078, a 140 F. t'stat. The temp. sensor is Merc. PN 806490T. Try a new Merc. t'stat.
 
the t stat is all new. It did this before I had the engine rebuilt. Now that it is all back together and running, I want it all right. I think I might just have the wrong sending unit. Will order one and see if it changes anything. Wrong OHMS is what I think.
 
why don't you take a variable resistor, hook it up to the gauge, and adjust the thing to get full deflection. Disconnect it and measure its resistance. Most will go full scale ~ 33 ohms and show the min value at 240 ohms. This is the common US standard. Some gauge makers use a different standard and I know one of them uses the reverse sense (less ohms provides full deflection). Once you know what you need, you can order the correct part and be done. Only other variabble is the single-dual station 'option' with the US standard.
 
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