temp gauge not working??????? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

coldgin · 05-25-2013, 08:25 PM

I have a 69 gmc 3/4 ton that I have retrofitted tbi injection on the stock 350...out of the blue temp gauge stops working and is pegged to the cold side....I grounded the wire going to the temp sending unit and the gauge pegged to the hot so I thought install new sending unit would fix my problem but the gauge is still pegged to the cold side...only thing I am wandering is the heater hose return hose goes to the pump instead of the radiator like on the late model I got my tbi from...I also changed thermostat thinking it might be stuck open and not letting the engine warm up...any ideas and I very open to suggestions...

Shyguy · 05-25-2013, 08:33 PM

What year is the sending unit you are using in the engine?

coldgin · 05-25-2013, 08:42 PM

stock 69 sending unit

Square_78 · 05-25-2013, 11:44 PM

Replace the wire from the sending unit to the gauge. Might be broken. Also check the connection at the sending unit and make sure it's really clean. That was the problem on mine.
Posted via Mobile Device

**VetteVet** · 05-26-2013, 10:31 AM

[QUOTE=coldgin;6090220]I have a 69 gmc 3/4 ton that I have retrofitted tbi injection on the stock 350...out of the blue temp gauge stops working and is pegged to the cold side....I grounded the wire going to the temp sending unit and the gauge pegged to the hot so I thought install new sending unit would fix my problem but the gauge is still pegged to the cold side...only thing I am wandering is the heater hose return hose goes to the pump instead of the radiator like on the late model I got my tbi from...I also changed thermostat thinking it might be stuck open and not letting the engine warm up...any ideas and I very open to suggestions...[/QUOTE

Has the gauge worked since you changed to TBI?

Grounding the sending unit wire shows two things A. the gauge is responding as it should and B. the wire is not open to the gauge.
This leaves the sending unit as the problem. Especially since the gauge was working before.

When you changed to TBI did you mount the gauge anywhere besides the left cylinder head and did you uses any sealer on the sender threads?

The heater hose does not have anything to do with the temperature gauge. You could have the heater hose disconnected and plugged and the gauge would still work.

coldgin · 05-27-2013, 12:09 AM

I did use sealer on the threads...do you think it is causing a bad ground?

coldgin · 05-27-2013, 12:11 AM

vette the sending unit is still in the left head...never moved it and was the original sending unit...

**VetteVet** · 05-27-2013, 02:32 AM

Quote:

Originally Posted by coldgin

I did use sealer on the threads...do you think it is causing a bad ground?

check for continuity between the sender body and the cylinder head, if you get infinity ohms then you're not getting a ground. There is a sealant that is electrically conductive, but I don't know the brand name offhand. If you don't have an ohm meter then just take the wire off the sender and touch the sender body and watch for the gauge to go hot. Key on of course.

coldgin · 05-29-2013, 09:42 PM

I was driving the truck the other day and I noticed when I turned the key on the needle would fall all the way past the "c"....when I turn the key off the needle would come right up to the edge of the "c"....I am thinking it was doing this with the old sending unit...beginning to think it is the gauge...anything else I need to check?

05-25-2013, 08:25 PM	#1
coldgin Registered User Join Date: Mar 2012 Location: maryville tn Posts: 33	temp gauge not working??????? I have a 69 gmc 3/4 ton that I have retrofitted tbi injection on the stock 350...out of the blue temp gauge stops working and is pegged to the cold side....I grounded the wire going to the temp sending unit and the gauge pegged to the hot so I thought install new sending unit would fix my problem but the gauge is still pegged to the cold side...only thing I am wandering is the heater hose return hose goes to the pump instead of the radiator like on the late model I got my tbi from...I also changed thermostat thinking it might be stuck open and not letting the engine warm up...any ideas and I very open to suggestions...

05-25-2013, 08:33 PM	#2
Shyguy Junior Member Join Date: Dec 2006 Location: Southeast Missouri Posts: 2,436	Re: temp gauge not working??????? What year is the sending unit you are using in the engine? __________________ '67 Chevy C-20 short stepper - build complete, 454/SM-465. '75 C-30 Single Cab DRW-350 small block/NP-435. '77 GMC-6500 Dump Truck, 427 Tall Deck. '92 GMC K-3500 Duallie, 454/4L80E.

05-25-2013, 08:42 PM	#3
coldgin Registered User Join Date: Mar 2012 Location: maryville tn Posts: 33	Re: temp gauge not working??????? stock 69 sending unit

05-25-2013, 11:44 PM	#4
Square_78 Registered User Join Date: Mar 2012 Location: Okanagan Valley, BC, Canada Posts: 1,237	Re: temp gauge not working??????? Replace the wire from the sending unit to the gauge. Might be broken. Also check the connection at the sending unit and make sure it's really clean. That was the problem on mine. Posted via Mobile Device __________________ #teamlongbed "I refuse to go disc brakes. I actually love drum brakes. It makes for an adventure." - 50bomb 1978 Chevy shop truck - static 6/8" 1970 GMC 1500 - Accuair eLevel Resto-mod http://67-72chevytrucks.com/vboard/s...d.php?t=537497

05-26-2013, 10:31 AM	#5
VetteVet Msgt USAF Ret Join Date: Jan 2005 Location: Kalamazoo, Michigan Posts: 8,709	Re: temp gauge not working??????? [QUOTE=coldgin;6090220]I have a 69 gmc 3/4 ton that I have retrofitted tbi injection on the stock 350...out of the blue temp gauge stops working and is pegged to the cold side....I grounded the wire going to the temp sending unit and the gauge pegged to the hot so I thought install new sending unit would fix my problem but the gauge is still pegged to the cold side...only thing I am wandering is the heater hose return hose goes to the pump instead of the radiator like on the late model I got my tbi from...I also changed thermostat thinking it might be stuck open and not letting the engine warm up...any ideas and I very open to suggestions...[/QUOTE Has the gauge worked since you changed to TBI? Grounding the sending unit wire shows two things A. the gauge is responding as it should and B. the wire is not open to the gauge. This leaves the sending unit as the problem. Especially since the gauge was working before. When you changed to TBI did you mount the gauge anywhere besides the left cylinder head and did you uses any sealer on the sender threads? The heater hose does not have anything to do with the temperature gauge. You could have the heater hose disconnected and plugged and the gauge would still work. __________________ VetteVet metallic green 67 stepside 74 corvette convertible 1965 Harley sportster 1995 Harley wide glide Growing old is hell, but it beats the alternative.

05-27-2013, 12:09 AM	#6
coldgin Registered User Join Date: Mar 2012 Location: maryville tn Posts: 33	Re: temp gauge not working??????? I did use sealer on the threads...do you think it is causing a bad ground?

05-27-2013, 12:11 AM	#7
coldgin Registered User Join Date: Mar 2012 Location: maryville tn Posts: 33	Re: temp gauge not working??????? vette the sending unit is still in the left head...never moved it and was the original sending unit...

05-29-2013, 09:42 PM	#9
coldgin Registered User Join Date: Mar 2012 Location: maryville tn Posts: 33	Re: temp gauge not working??????? I was driving the truck the other day and I noticed when I turned the key on the needle would fall all the way past the "c"....when I turn the key off the needle would come right up to the edge of the "c"....I am thinking it was doing this with the old sending unit...beginning to think it is the gauge...anything else I need to check?



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