Water Temp Gauge screwy behavior - The 1947 - Present Chevrolet & GMC Truck Message Board Network

elektrik · 03-13-2008, 08:02 AM

Need some help on where to start troubleshooting my factory temp gauge. It was working fine just a few weeks ago, when I started to notice some extremely odd behavior:

- First, it occasionally jumped all the way to hot extremely quickly (Ex. from cold to hot within .5 seconds) and back down to cold. It would do this back and forth randomly with no pattern. It was as iff someone were making the gauge go short to ground and then back...

- Then, as time went on, the behavior kept getting more consistent. More cold to hot bouncing, and finally the gauge stopped working all together (it's stuck on cold even when the truck's running).

Anyone have any suggestions where to start first? I want to get this thing fixed before the HOT HOT summer in San Antonio starts (which is soon, sadly

)

Thanks in advance

Andy4639 · 03-13-2008, 08:55 AM

Check the wiring it maybe shorting out. Also check where it goes into the fuse block on the driver's side firewall. Then again it maybe the sendor itself going bad.

jorgensensc · 03-13-2008, 09:04 AM

Make sure the wire is not shorting out against the exhaust manifold. I can't tell you the number of time I've had to replace that wire because it leaned against the manifold and burned through and shorted out.
Shawn

berencam · 03-13-2008, 12:46 PM

im going to go out on a limb here and say its your voltage regulator. see your temp gauge works off resistance, the hotter the engine is the less(or more cant remember what one) resistance you have going through your sensor. So when your voltage regulator goes out you have way more volts on everything so it throws the resistances all off. I would first start with the wire on the temp gauge itself, then trace it to the gauge cluster, then check all wire going to the voltage regulator. Also check to make sure the regulator has a good ground.

Wreckless_71 · 03-13-2008, 08:34 PM

I tend to agree with Jorgenson on this one 'cause my wire comes off the sending unit every once in a while and get burned on the headers...start there.

cruiserman · 03-13-2008, 09:32 PM

If the wiring checks out, burp air out of the cooling system.

Brad · 03-14-2008, 11:48 AM

I'm having similar problems after changing my water pump, but I'm pretty sure that it's just air in the system as I've encountered the same thing after opening up the cooling system. It usually takes a few weeks to work it's way out and I end up having to add H2O/coolant until it passes.

elektrik · 03-17-2008, 07:56 PM

Quote:

Originally Posted by jorgensensc

Make sure the wire is not shorting out against the exhaust manifold. I can't tell you the number of time I've had to replace that wire because it leaned against the manifold and burned through and shorted out.
Shawn

Ok, I'm going to attack it from this angle first, since I have a new voltage regulator (and I'm going off the assumption that it works perfectly)

So, with that said, this non-mechanic doesn't have the slightest clue of *which* wire to look for, or where for that matter.

Anyone wanna clue me int?

71 super · 03-17-2008, 08:10 PM

Check the sending unit for the guage. I had a 250 that would do the same thing and it usually occured when idling in a drive thru???, anyway the sending unit was grounding out on it's self, after it was changed (cheap) enerything was fine.

elektrik · 03-19-2008, 06:18 AM

Quote:

Originally Posted by 71 super

Check the sending unit for the guage. I had a 250 that would do the same thing and it usually occured when idling in a drive thru???, anyway the sending unit was grounding out on it's self, after it was changed (cheap) enerything was fine.

Yes, but *where* is it? I'm not even sure what to look for, let alone where. I can figure out electronics/electrical, but it'd be a whole lot easier if I didn't have to figure which wire starting from the fuse block...

72BLUZ · 03-19-2008, 07:13 AM

i say you need a resistor at the back of the gauge or you have lost the ground for that gauge. mine did the same thing. i connected a ground to the gauge and it started working.

Rollie396 · 03-19-2008, 10:22 AM

I could be a bit off on this,but if it's a 350,chances are good that the temp sender will be found on the driver side of the engine on the block between 1 and 3 cylinders.there will be a brass fitting sticking out,with a wire coming out of it.

elektrik · 03-19-2008, 04:12 PM

Quote:

Originally Posted by Rollie396

I could be a bit off on this,but if it's a 350,chances are good that the temp sender will be found on the driver side of the engine on the block between 1 and 3 cylinders.there will be a brass fitting sticking out,with a wire coming out of it.

Thanks..I'll start there

elektrik · 03-25-2008, 10:37 PM

Ok, so I've started my troubleshooting, and I decided to start with the KISS principle. Everything's connected, so I went to the next step. I pulled out my multimeter and read the voltage on each side of the gauge terminal to see what it was. On one side, I was reading 11V and the other terminal was 13. (I tested the battery gauge to see if I were going to read similar voltages, which I do).

So....

I need some consensus-do you guys think I should start with replacing the gauge, since it has proper voltage but doesn't read *anything* or am I missing something?

**DANTIP** · 03-25-2008, 10:47 PM

I had the same problem and it was the voltage regulator. One other symptom was the alternator seemed to be more noisy (probably because it was charging when it should not have been). Replaced the regulator and everything is "playing nice".

Good Luck!

elektrik · 03-25-2008, 10:51 PM

I'm hoping it's not the regulator, since it's *new* (ok, 2 months old now)

berencam · 03-25-2008, 11:39 PM

im still going with the regulator. I bought a new one, installed it, and before i got home(30 minute drive) it blew out again. So dont bet on that regulator being good even though you just replaced it.

**DANTIP** · 03-25-2008, 11:52 PM

If the gauge is not damaged, I believe you could rule out the regulator by removing your alternator belt and running the engine (it will start and run fine for the test). If the gauge works, the regulator is probably the problem. If it doesn't work there may be another problem or the excessive voltage could have damaged the guage or resistor.

Longhorn Man · 03-26-2008, 12:20 AM

to test the regulator, check the battery voltage while running at variouse RPMs. Once you see it is fine, move on.
Very unlikely to be the regulator. He'd be talking about headlights getting drighter at times, and flashers that speed up and slow down, and a funny (battery) smell.

elektrik · 03-26-2008, 02:01 AM

I fixed it-you're gonna love this:

I don't think the temperature gauge was connected correctly for a *very* long time!

The sensor didn't have ANY wire anywhere near the sensor, which was throwing me off because it was WORKING 1 month ago and I know for a fact that there was no wire anywhere near that area...

I think someone connected the temp gauge incorrectly (we lovingly refer to it as "mickey rigging"), which means it probably wasn't even reading the temperature!

After hunting down the wire and reconnecting it to the sensor, my gauge started working again-however, I don't have the "fitting" for it-just kinda wrapped the wire around the sensor....

Anyone know where I can get the correct wire fitting? Any parts store?

Brad · 03-26-2008, 08:15 PM

Napa sells the connector.

elektrik · 03-27-2008, 02:05 AM

nice...thanks for the info

Cracksrubi · 04-04-2013, 10:15 PM

What color is the wire someone cut it out of a long time ago and I'm trying to reuse stock gauges or postion on fuse block
Posted via Mobile Device

**VetteVet** · 04-04-2013, 10:59 PM

Here is a diagram to show how the wire runs and the color. the temp sensor is just left of the engine block in the diagram and the color is medium green unless someone has changed it.

Attachment 1087240

elektrik · 04-05-2013, 01:11 PM

Wow...old thread. I remember the problem like yesterday though

Seriously though-someone just cut the wire and connected it to (some other one, don't remember now). I had to put a connector back on it and hook it up to the ACTUAL temperature sensor....

...Now if I could JUST find an easy way to fix the wing window frame.... lol.

03-13-2008, 08:02 AM	#1
elektrik Foolish Mortal Join Date: Mar 2007 Location: Livermore, CA Posts: 243	Water Temp Gauge screwy behavior Need some help on where to start troubleshooting my factory temp gauge. It was working fine just a few weeks ago, when I started to notice some extremely odd behavior: - First, it occasionally jumped all the way to hot extremely quickly (Ex. from cold to hot within .5 seconds) and back down to cold. It would do this back and forth randomly with no pattern. It was as iff someone were making the gauge go short to ground and then back... - Then, as time went on, the behavior kept getting more consistent. More cold to hot bouncing, and finally the gauge stopped working all together (it's stuck on cold even when the truck's running). Anyone have any suggestions where to start first? I want to get this thing fixed before the HOT HOT summer in San Antonio starts (which is soon, sadly ) Thanks in advance

03-13-2008, 08:55 AM	#2
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,936	Re: Water Temp Gauge screwy behavior Check the wiring it maybe shorting out. Also check where it goes into the fuse block on the driver's side firewall. Then again it maybe the sendor itself going bad. __________________ 1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.

03-13-2008, 09:04 AM	#3
jorgensensc Registered User Join Date: Jul 2003 Location: Cypress, Tx Posts: 4,005	Re: Water Temp Gauge screwy behavior Make sure the wire is not shorting out against the exhaust manifold. I can't tell you the number of time I've had to replace that wire because it leaned against the manifold and burned through and shorted out. Shawn __________________ 1972 C20 Suburban- Big Blue Betty '56 Chevy Bel Air Sedan- Frame up Restoration -What would you attempt to achieve if you knew you could not fail?- -I Refuse To Tiptoe Through Life, Only To Arrive Safely At Death's Door- R.I.P. EAST SIDE LOW LIFE

03-13-2008, 12:46 PM	#4
berencam Registered User Join Date: Aug 2007 Location: branson mo Posts: 933	Re: Water Temp Gauge screwy behavior im going to go out on a limb here and say its your voltage regulator. see your temp gauge works off resistance, the hotter the engine is the less(or more cant remember what one) resistance you have going through your sensor. So when your voltage regulator goes out you have way more volts on everything so it throws the resistances all off. I would first start with the wire on the temp gauge itself, then trace it to the gauge cluster, then check all wire going to the voltage regulator. Also check to make sure the regulator has a good ground. __________________ 69 chevy c10 350 3 speed manual wood bed build thread here r.i.p. 70 c10 auto 350 build here

03-13-2008, 08:34 PM	#5
Wreckless_71 Registered User Join Date: Apr 2007 Location: Kelso, WA Posts: 363	Re: Water Temp Gauge screwy behavior I tend to agree with Jorgenson on this one 'cause my wire comes off the sending unit every once in a while and get burned on the headers...start there. __________________ 1972 K10 4" lift, 35’s, 383 stroker, 700r4, current project. 1971 C10 3"/5" static drop, 355/350. "La Bamba.” The current daily driver.

03-13-2008, 09:32 PM	#6
cruiserman Registered User Join Date: Dec 2006 Location: Idaho Posts: 210	Re: Water Temp Gauge screwy behavior If the wiring checks out, burp air out of the cooling system. __________________ 72 C2500 LWB 402 Sierra Grande 05 Odyssey 08 Tundra

03-14-2008, 11:48 AM	#7
Brad Out of the carpool lane. Join Date: Jan 2000 Location: Clark Co, WA Posts: 5,673	Re: Water Temp Gauge screwy behavior I'm having similar problems after changing my water pump, but I'm pretty sure that it's just air in the system as I've encountered the same thing after opening up the cooling system. It usually takes a few weeks to work it's way out and I end up having to add H2O/coolant until it passes. __________________ 1968 C-10 SWB, 5.7 Vortec/700R4/3.73 posi, Torch Red 1968 Camaro, 250/Powerglide, all original (No, I'm not gonna drop a 350 in it!...Jeez!) 2000 Honda VFR in the faster yellow! 2008 Husqvarna TE-610 1967 C-10 SWB 'Six Appeal'-Gone but not forgotten...

03-17-2008, 08:10 PM	#9
71 super Registered User Join Date: Sep 2005 Location: Canton North carolina Posts: 3,079	Re: Water Temp Gauge screwy behavior Check the sending unit for the guage. I had a 250 that would do the same thing and it usually occured when idling in a drive thru???, anyway the sending unit was grounding out on it's self, after it was changed (cheap) enerything was fine.

03-19-2008, 07:13 AM	#11
72BLUZ Registered User Join Date: Nov 2006 Location: lafayette, ga. Posts: 832	Re: Water Temp Gauge screwy behavior i say you need a resistor at the back of the gauge or you have lost the ground for that gauge. mine did the same thing. i connected a ground to the gauge and it started working. __________________ Freedom is never more than one generation away from extinction. We didn't pass it to our children in the bloodstream. It must be fought for, protected, and handed on for them to do the same.... Ronald Reagan

03-19-2008, 10:22 AM	#12
Rollie396 someday it will be done! Join Date: Sep 2004 Location: Lloydminster,AB. Canada Posts: 1,620	Re: Water Temp Gauge screwy behavior I could be a bit off on this,but if it's a 350,chances are good that the temp sender will be found on the driver side of the engine on the block between 1 and 3 cylinders.there will be a brass fitting sticking out,with a wire coming out of it. __________________ '72 C-10 Proud owner of a million new and used pieces that used to be and will once again be(god willing) a testament to the term "they don't build em like that anymore. '80 LWB 2wd beater '67 GMC long fleet (cab donor) '66 long step (parked till it's turn comes around) '65 short step (parts truck that will donate it's bed and possibly frame to the '66) '06 Grand Prix wife's car (she hardly lets me touch it) my pics

03-25-2008, 10:37 PM	#14
elektrik Foolish Mortal Join Date: Mar 2007 Location: Livermore, CA Posts: 243	Re: Water Temp Gauge screwy behavior Ok, so I've started my troubleshooting, and I decided to start with the KISS principle. Everything's connected, so I went to the next step. I pulled out my multimeter and read the voltage on each side of the gauge terminal to see what it was. On one side, I was reading 11V and the other terminal was 13. (I tested the battery gauge to see if I were going to read similar voltages, which I do). So.... I need some consensus-do you guys think I should start with replacing the gauge, since it has proper voltage but doesn't read anything or am I missing something?

03-25-2008, 10:47 PM	#15
DANTIP Registered User Join Date: Sep 2001 Location: Fort Wayne, Indiana, USA Posts: 1,882	Re: Water Temp Gauge screwy behavior I had the same problem and it was the voltage regulator. One other symptom was the alternator seemed to be more noisy (probably because it was charging when it should not have been). Replaced the regulator and everything is "playing nice". Good Luck!

03-25-2008, 10:51 PM	#16
elektrik Foolish Mortal Join Date: Mar 2007 Location: Livermore, CA Posts: 243	Re: Water Temp Gauge screwy behavior I'm hoping it's not the regulator, since it's new (ok, 2 months old now)

03-25-2008, 11:39 PM	#17
berencam Registered User Join Date: Aug 2007 Location: branson mo Posts: 933	Re: Water Temp Gauge screwy behavior im still going with the regulator. I bought a new one, installed it, and before i got home(30 minute drive) it blew out again. So dont bet on that regulator being good even though you just replaced it. __________________ 69 chevy c10 350 3 speed manual wood bed build thread here r.i.p. 70 c10 auto 350 build here

03-25-2008, 11:52 PM	#18
DANTIP Registered User Join Date: Sep 2001 Location: Fort Wayne, Indiana, USA Posts: 1,882	Re: Water Temp Gauge screwy behavior If the gauge is not damaged, I believe you could rule out the regulator by removing your alternator belt and running the engine (it will start and run fine for the test). If the gauge works, the regulator is probably the problem. If it doesn't work there may be another problem or the excessive voltage could have damaged the guage or resistor.



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03-26-2008, 12:20 AM	#19
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: Water Temp Gauge screwy behavior to test the regulator, check the battery voltage while running at variouse RPMs. Once you see it is fine, move on. Very unlikely to be the regulator. He'd be talking about headlights getting drighter at times, and flashers that speed up and slow down, and a funny (battery) smell.

03-26-2008, 02:01 AM	#20
elektrik Foolish Mortal Join Date: Mar 2007 Location: Livermore, CA Posts: 243	Re: Water Temp Gauge screwy behavior I fixed it-you're gonna love this: I don't think the temperature gauge was connected correctly for a very long time! The sensor didn't have ANY wire anywhere near the sensor, which was throwing me off because it was WORKING 1 month ago and I know for a fact that there was no wire anywhere near that area... I think someone connected the temp gauge incorrectly (we lovingly refer to it as "mickey rigging"), which means it probably wasn't even reading the temperature! After hunting down the wire and reconnecting it to the sensor, my gauge started working again-however, I don't have the "fitting" for it-just kinda wrapped the wire around the sensor.... Anyone know where I can get the correct wire fitting? Any parts store?

03-26-2008, 08:15 PM	#21
Brad Out of the carpool lane. Join Date: Jan 2000 Location: Clark Co, WA Posts: 5,673	Re: Water Temp Gauge screwy behavior Napa sells the connector. __________________ 1968 C-10 SWB, 5.7 Vortec/700R4/3.73 posi, Torch Red 1968 Camaro, 250/Powerglide, all original (No, I'm not gonna drop a 350 in it!...Jeez!) 2000 Honda VFR in the faster yellow! 2008 Husqvarna TE-610 1967 C-10 SWB 'Six Appeal'-Gone but not forgotten...

03-27-2008, 02:05 AM	#22
elektrik Foolish Mortal Join Date: Mar 2007 Location: Livermore, CA Posts: 243	Re: Water Temp Gauge screwy behavior nice...thanks for the info

04-04-2013, 10:15 PM	#23
Cracksrubi Registered User Join Date: Oct 2012 Location: Hazel Green Al Posts: 54	Re: Water Temp Gauge screwy behavior What color is the wire someone cut it out of a long time ago and I'm trying to reuse stock gauges or postion on fuse block Posted via Mobile Device __________________ 68 c-10 lwb

04-04-2013, 10:59 PM	#24
VetteVet Msgt USAF Ret Join Date: Jan 2005 Location: Kalamazoo, Michigan Posts: 8,709	Re: Water Temp Gauge screwy behavior Here is a diagram to show how the wire runs and the color. the temp sensor is just left of the engine block in the diagram and the color is medium green unless someone has changed it. Attachment 1087240 Attached Images __________________ VetteVet metallic green 67 stepside 74 corvette convertible 1965 Harley sportster 1995 Harley wide glide Growing old is hell, but it beats the alternative.

04-05-2013, 01:11 PM	#25
elektrik Foolish Mortal Join Date: Mar 2007 Location: Livermore, CA Posts: 243	Re: Water Temp Gauge screwy behavior Wow...old thread. I remember the problem like yesterday though Seriously though-someone just cut the wire and connected it to (some other one, don't remember now). I had to put a connector back on it and hook it up to the ACTUAL temperature sensor.... ...Now if I could JUST find an easy way to fix the wing window frame.... lol.

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