1990 chevy 305 temp gauge funny buisness

CHEVY2003 · 08-02-2008, 04:11 AM

Hello,

Just purchased a 1990 chevy single cab 4x2 swb Thursday. Friday I have it put on a computer and the Water Temp gauge read bad and the Throttle positioner i believe was bad. I had the throttle positioner changed Thursday night and then Friday afternoon after sleeping all day got up at 4:45 p.m. went to my truck started it up and it went all the way over to hot. I went to my cousins house and he replaced the temp sending unit, but still the gauge is all the way to hot. He had it on the computer and it read 190. What is the problem here. I am or was a die hard Dodge diesel man, but wanted a older chevy. Can anyone help me on this

stumpuller454 · 08-02-2008, 09:10 AM

could be a short to ground or open, can`t remember if unhooking it goes to the hot or cold side, but if you unplug it what does the gauge read? if there is no change, consider faulty wiring...does the gauge read hot ALL the time?

hotrodpc · 08-02-2008, 10:04 AM

I am with stump on this one. And I do believe if it is grounded, it will go full hot. Sound like there is dead ground short somewhere on that temp sensor wire. And are you sure you got a sensor for a guage and not an idiot light. There is certainly a difference.

leolkfrm · 08-02-2008, 12:57 PM

It's a plug in dash, Make sure it is making contact at the main plug

CHEVY2003 · 08-02-2008, 08:37 PM

Well he did unplug the wire from the sending unit and no change in the temp reading. He had it on the computer and it read before we changed the parts was throwing a code for bad temp sending unit and throttle positioner both parts were replaced, but still yet the temp gauge in on hot all the time and the check gagues light comes on of course, but the computer is showing 190 degrees when the truck gauge is showing 260 so what's the problem folks???

hotrodpc · 08-03-2008, 01:10 AM

Being that even with the wire disconnected it still the same and no change, I am still going with the thought, somewhere that wire between the sensor and the guage is grounded somewhere. It could possibly even be grounded at the instrument cluster.

CHEVY2003 · 08-03-2008, 01:44 AM

Hmm and how do i fix that??

08-02-2008, 04:11 AM	#1
CHEVY2003 Junior Member Join Date: Aug 2008 Posts: 3	1990 chevy 305 temp gauge funny buisness Hello, Just purchased a 1990 chevy single cab 4x2 swb Thursday. Friday I have it put on a computer and the Water Temp gauge read bad and the Throttle positioner i believe was bad. I had the throttle positioner changed Thursday night and then Friday afternoon after sleeping all day got up at 4:45 p.m. went to my truck started it up and it went all the way over to hot. I went to my cousins house and he replaced the temp sending unit, but still the gauge is all the way to hot. He had it on the computer and it read 190. What is the problem here. I am or was a die hard Dodge diesel man, but wanted a older chevy. Can anyone help me on this

08-02-2008, 09:10 AM	#2
stumpuller454 Senior Member Join Date: Dec 2007 Location: Alberta Posts: 895	could be a short to ground or open, can`t remember if unhooking it goes to the hot or cold side, but if you unplug it what does the gauge read? if there is no change, consider faulty wiring...does the gauge read hot ALL the time? __________________ 1998 GMC K2500 Ext.cab short box 454ci (supercharger coming soon!) *1951 Chevrolet 1420 pickup like new!* Red seal certified Journeyman Automotive Mechanic

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08-02-2008, 10:04 AM	#3
hotrodpc Senior Member Join Date: Jul 2008 Posts: 108	I am with stump on this one. And I do believe if it is grounded, it will go full hot. Sound like there is dead ground short somewhere on that temp sensor wire. And are you sure you got a sensor for a guage and not an idiot light. There is certainly a difference.

08-02-2008, 12:57 PM	#4
leolkfrm Senior Member Join Date: Mar 2008 Location: N.Y. Posts: 1,074	It's a plug in dash, Make sure it is making contact at the main plug

08-02-2008, 08:37 PM	#5
CHEVY2003 Junior Member Join Date: Aug 2008 Posts: 3	Well he did unplug the wire from the sending unit and no change in the temp reading. He had it on the computer and it read before we changed the parts was throwing a code for bad temp sending unit and throttle positioner both parts were replaced, but still yet the temp gauge in on hot all the time and the check gagues light comes on of course, but the computer is showing 190 degrees when the truck gauge is showing 260 so what's the problem folks???

08-03-2008, 01:10 AM	#6
hotrodpc Senior Member Join Date: Jul 2008 Posts: 108	Being that even with the wire disconnected it still the same and no change, I am still going with the thought, somewhere that wire between the sensor and the guage is grounded somewhere. It could possibly even be grounded at the instrument cluster.

08-03-2008, 01:44 AM	#7
CHEVY2003 Junior Member Join Date: Aug 2008 Posts: 3	Hmm and how do i fix that??