New Temp Gauge and New Temp Sending Unit Not Playing Well To

[signsup]

Put new temp sending unit and new temp gauge in truck and gauge reads down to zero when cold, then warms up and then pegs out at 260 or so and it is clear with manual thermal temp gun that I'm not that hot and hot overheating. Read the test specs for the sending unit and it reads within the OHMS range. So I'm thinking gauge, but don't know how to test it or what to purchase as a replacement to insure that it is speaking the same language as the sending unit. The sending unit was a little cloudy on what it would fit, mentions large trucks and also mentions M37 and M38A1 so I don't know if all sending units will work on all M series engines.

Here is sending unit I got:

https://www.ebay.com/itm/Temperature-Se ... 2749.l2649

and this is the actual temp gauge installed:

https://www.ebay.com/itm/N-O-S-Jeep-Wil ... SwAdhcbhPL

Any direction greatly appreciated.

[NAM VET]

perhaps an air lock at the rear of the head, where the sender is. Reading steam? That is a hot place on the head. Maybe take off top hose, and try to fill head. Keep us informed.

NV

[sturmtyger380]

I think that gauge and sender are not matched. The dash gauge is expecting a certain OHMs to be sent from the sender.

I looked up that sender and it looks like it's for the Temp Range - 120 - 320 degrees.

[signsup]

Hmmmm..I searched the part number and this is what I found...

Product Description

Temperature sending unit MS24537-1, alternate numbers MIL-I-10986F, 7389566. NSN 6685008145271. Replaces old P/N 804873. Also replaces P/N 142511, NSN 6685000424165. For water or oil. For use on military trucks such as M35A2, M54A2, M809, M939, etc also other military equipment such as generator sets, fork lifts, etc. Uses standard rubber shell electrical connector. 1/2 inch pipe thread.
Will function with both MS24543-2 and 11669355 gauges.
Use this sender for the M939 series transmission oil temp and engine water temp.

0.2 lb


Approximate sending unit resistance readings:
2.53 KOhms at 120 F
970 Ohms at 200

So, they are giving resistance readings for the lower temperature, much more in line with the M37 and the vehicles they list are the Humvee type oil and water temperature, which I would think would be in the 200 range or lower. We did clean up the grounds well and got it to stop at 220 degrees, wo we will run it like this and see if it pegs out again. Took thermal readings of engine and we are not running this hot. Just reading that we are.

[just me]

I had to calibrate and install a resistor in line between the gauge and sender with mine to get accurate readings. (Same sender from mecoparts.)Works fine now.

[NAM VET]

My older temp gage was reading a bit high, say 15-degrees or so, so ordered a new gage and sender from Charles T at M 37 Rebuild, all good now.

I wouldn't know how to add a resister to my wiring. In fact, I have never understood in a vehicle, how an electron going to and then thru some gage or switch, can find it's way back to the battery, and not get just lost somewhere. NV

[vit16]

imagine that electron is just water dropped to the floor. if you do that, water will go to the lowest place finding the most easiest way to do it.
that is the explanation. negative is the lowest point!!