Temp Gauge Sending Unit

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bbook

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I purchased a NOS temp gauge with sending unit and line (#68-10883) for my 36 1.5 ton. When I pulled the old sending unit from the water pump, it didn't have the 1 1/2 inch "probe" the new one has, but did have what could be the base of a probe. The probe for the new gauge won't fit through the opening with reasonable pressure applied.

In the attached picture, the old sending unit is on the left and the new is on the right. It does not appear as though an old probe was left behind in the pump, as I can see in and can put a screwdriver into the opening all the way to the other side of the pump.

Are there different types of sending units, perhaps for cars versus trucks? I thought it worth checking before I try to expand the opening in the pump and push harder on the new sending unit probe. Any thoughts would be appreciated.
 

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Old is just a plug and there to plug the hole and make it look like original. The RH one is original sending unit. The hole in the pump is most likely partially plugged from rust. since there has not been a proper sending unit in the hole for a long time.
 
I carefully scraped the hole into the water pump housing and the sending unit slid right in. Pictured is the gauge at operating temperature. The bright red is great. It seems to hang in the upper two thirds of the NORMAL range at operating temperature. As long as I have a basis point, I'm good with it, but I'm curious as to whether there is any method of calibration of these gauges.
 

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In '37 Ford had the degrees printed as part of the graphics.Looks like its at about 160.The top line would be about 180.IMO
 
Not sure on the '36, but the 37-39 has an etched calibration mark on the back side of the glass to indicate 212º. The glass is adjustable up or down to align with the printed temp value.

A pain now that you have it installed, but you could have put the sender in a pot of boiling water to verify the 212º calibration. Used units could have a dented sender which could throw off the calibration.
 
I did check the unit in hot water after I purchased it, just to be sure it worked, but I didn't think to note the height at boiling. Good tip.

I'll watch the gauge readings for a while. I'm just starting to drive the truck after finally getting far enough along with restoration. I'll probably have the gauge out of the dash again and will check to see if there is an etched mark on the sight glass.

Thanks to all for the help.
 
Terry said:
Old is just a plug and there to plug the hole and make it look like original. The RH one is original sending unit. The hole in the pump is most likely partially plugged from rust. since there has not been a proper sending unit in the hole for a long time.
Click to expand...

Good troubleshooting there Terry,OH. Credit where credit is due.

Lonnie
 
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