oil pressure and water temp sending units (two part question)

texasred · July 29th, 2007, 11:41 AM

Part 1. I have nothing but my own observations on this...so please correct me if I am wrong. Mid 60s through mid 80s GM factory oil pressure sending units for "idiot lights" are "always" kinda flat as opposed to the factory oil pressure sending units for gauges which are "always" kinda bulb-shaped.

Part 2. Can you tell the difference between water temp sending units for "idiot lights" and gauges by visual inspection alone? I found some strays recently.

Thanks in advance.

C.J.

J-(Chicago) · July 29th, 2007, 01:31 PM

That reminds me... if anyone doesn't have that special oldsmobile shaped socket. A store a few miles down the road had a couple and had no idea what they were for. If anyone needs one let me know and I'll pick em up if they are still there.

smcurro · July 31st, 2007, 11:00 AM

The water temp sending unit for the idiot light has a regular prong set in bacalite plastic at the top. The sending unit for the gauge has a round connection which the plug slides onto sideways. If your still not sure you can test them out. The sending unit for the idiot light should have a very high resistance at normal temperatures because the switch is open. You can heat up the sensor on an electric stove (be very careful) and watch as the resistance suddenly drops to zero when the switch closes. The sending unit for the gauge will only change in resistance slowly as it is heated up and will never have a sudden change because it is a variable resistor rather than a switch. I hope that helps, if you have any questions let me know.

texasred · July 31st, 2007, 11:18 AM

Quote:

Originally Posted by smcurro

The water temp sending unit for the idiot light has a regular prong set in bacalite plastic at the top. The sending unit for the gauge has a round connection which the plug slides onto sideways. If your still not sure you can test them out. The sending unit for the idiot light should have a very high resistance at normal temperatures because the switch is open. You can heat up the sensor on an electric stove (be very careful) and watch as the resistance suddenly drops to zero when the switch closes. The sending unit for the gauge will only change in resistance slowly as it is heated up and will never have a sudden change because it is a variable resistor rather than a switch. I hope that helps, if you have any questions let me know.

That was my experience until I bought a 72 parts car with factory Rally Pak. The Water Temp sender has the spade termnal. Forgot about throwing it in a pan of hot water (DUH!)

C.J.

July 29th, 2007, 11:41 AM	#1 (permalink)
texasred Tom Servo's Stunt Double Join Date: Apr 2004 Location: San Antonio, Texas Posts: 824	oil pressure and water temp sending units (two part question) Part 1. I have nothing but my own observations on this...so please correct me if I am wrong. Mid 60s through mid 80s GM factory oil pressure sending units for "idiot lights" are "always" kinda flat as opposed to the factory oil pressure sending units for gauges which are "always" kinda bulb-shaped. Part 2. Can you tell the difference between water temp sending units for "idiot lights" and gauges by visual inspection alone? I found some strays recently. Thanks in advance. C.J. __________________ Dad said, "Sometimes you read Job...sometimes you ARE Job!"

July 29th, 2007, 01:31 PM	#2 (permalink)
J-(Chicago) Seasoned beater pilot. Join Date: Jan 2007 Location: Chicago Posts: 2,697	That reminds me... if anyone doesn't have that special oldsmobile shaped socket. A store a few miles down the road had a couple and had no idea what they were for. If anyone needs one let me know and I'll pick em up if they are still there. __________________ I'd rather have a numbers matching poker hand.

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July 31st, 2007, 11:00 AM	#3 (permalink)
smcurro Registered User Join Date: Jul 2007 Location: Belmont, MA Posts: 115	The water temp sending unit for the idiot light has a regular prong set in bacalite plastic at the top. The sending unit for the gauge has a round connection which the plug slides onto sideways. If your still not sure you can test them out. The sending unit for the idiot light should have a very high resistance at normal temperatures because the switch is open. You can heat up the sensor on an electric stove (be very careful) and watch as the resistance suddenly drops to zero when the switch closes. The sending unit for the gauge will only change in resistance slowly as it is heated up and will never have a sudden change because it is a variable resistor rather than a switch. I hope that helps, if you have any questions let me know.