1987 GMC Truck Temperature Gauge Question

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Ghettoboom767

Ghettoboom767

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Hi everyone,I have a GMC High Sierra 2500 and my only gauge that doesn't work is the temp gauge.
Is there a way to test the sensor? I'm hoping the gauge isn't bad,it reads 100 all the time which is where it sits when it's normally off.
I'd like to get this going,wondering if there is anyone that has had this problem with the older GM truck.
It has the 5.7 liter F.I. Engine.
I'd appreciate any input on this.😀
 
LJV

LJV

Member (SA)
Sensor can be tested by dipping in hot water.
This can happen for various reasons, the corrosion is main.
It could also be the burned or oxidated fuse, or demaged cable. Its really easy to check what is wrong. If fuse and cable that connect sensor and gauge are ok, than get new sensor. They are cheap and easy to replace.

Gauges usually never break, unless they are physically demaged.


Hope it helps.
 
-GZ-

-GZ-

Member (SA)
I had a similar problem with my old merc cougar. It started to read below 210...maybe not always 100.
The "floodgate" for your coolant could be stuck in the open position causing the actual temp of the motor to never get up to actual operating temperature. That's what the Bama boy told me that I bought it from. Don't know if there's any validity to it. I'm not that much of a car guy. Just food for thought.
 
LJV

LJV

Member (SA)
The temp would rise even if thermostat is stuck open. People used to take thermostats out during long distance travels in the summer heat to improve coolant flow and prevent overheating. If the radiator fan turns on, than temp gauge must indicate significant increase, close to red.
 
Cpl-Chronic

Cpl-Chronic

Member (SA)
Sounds like a fuse, broken wire or most likely a bad sending unit. Replace the sending unit first if the fuse is good which sounds like it since the rest of the instruments work. Most likely the sending unit failed for some reason so replacing it will eliminate the problem or eliminate the unit as the cause & you can work back from there to sort it out more quickly....

Cpl
 
trippy1313

trippy1313

Member (SA)
Usually with a temp sensor you can test it with a multimeter by reading the resistance/impedance within the (usually) 2 points in the plug. As the temp rises/falls the reading should change too.

But what it should read I don't know for your vehicle. But as long as it's changing, it must work to some extent.


With that being said, as CPL mentioned. Check fuses first. With ANY elictrical issue, check fuses first.
 
Ghettoboom767

Ghettoboom767

Member (SA)
jimmyjimmy19702010 said:
1987 model? Just replace the sender - cheap and easy to replace. I've had plenty of old senders fail but never a dash board gauge.
Click to expand...
Hi everyone for your advice,yes fan is new,thermostat is good,I'll just replace the sending unit,that's what I thought at first.
Gauge should be ok,it just doesn't rise at all from the bottom which is just below the 100 mark.
Ill look into getting one within the next 2-3 weeks as I'm not really driving it yet.
Still need front shocks,I love this truck but I have had to do quite a bit of work on it.
I just replaced the drivers side motor mount and that really sucked!! A temperature sending unit is nothing compared to that!!😮
 
floyd

floyd

Boomus Fidelis
don't feel bad jeff my truck started spewing brake fluid just as i was leaving for work , turns out my back brakes were just a dust collection being held together by rust . man i had to sweat my ass off under this basterd and still have more to do . i had to replace both rear wheel cylinders , the brake shoes and the hardware and bleed the brakes by myself. note to self at least pull your ****ing wheels off every 3 to 4 years just to see wtf is up lol.
 
Ghettoboom767

Ghettoboom767

Member (SA)
I have some leaking rear wheel cylinders and am getting them replaced along with the shoes.
I gave good brakes and there is decent thickness to the shoes but right after the front shocks I'm having this done but it's going to be $350-400.
Discs up front are good!
I know it has to be done,mine is a super heavy duty 3/4T 4 wheel drive so the axles have to be pulled,I won't be doing that job myself!
Floyd,I'm impressed that you did all that yourself!!
Good job.😀😎
 
floyd

floyd

Boomus Fidelis
thanks man it all cost under $100.00 bucks for parts , i basically won't let anyone work on my vehicles . i do it myself or the motherfarker sits lol. would have been easier if the rotten parts had not just fell on the ground when i pulled the rear drums off. and the farked up part is the drums were perfect everything else was dust. i been rebuilding my truck a little at a time , pretty soon the whole damn thing will be new . every time i work on it , it looses 10 pounds in rust crumbs from me pounding on something.
 
floyd

floyd

Boomus Fidelis
oh trust me i work on some trucks like f-350's and chevy 3500's , not one easy thing about it.
 
Ghettoboom767

Ghettoboom767

Member (SA)
Sounds like me and you are doing the same thing!
I always do as much as I can but I'm somewhat limited on tools and when it comes to drum brakes I let someone do it.
I'm slowly restoring this thing, it's a High Sierra and it's loaded!!
Somewhat rare, has a super HD susoension,5th.wheel hitch in the bed, ball no shackle though.
The really cool thing about my truck is that it's like 110% original-all manuals papers nothing been replaced, and NO RUST.
At least the body that is, very minimal on underneath for being 28 years old.
What are you working on?☺😎
 
Ghettoboom767

Ghettoboom767

Member (SA)
No aftermarket anything, all stickers and jack, original stereo, even original tailpipes!☺ still in good shape different mufflers though.
 
floyd

floyd

Boomus Fidelis
Ghettoboom767 said:
Sounds like me and you are doing the same thing!
I always do as much as I can but I'm somewhat limited on tools and when it comes to drum brakes I let someone do it.
I'm slowly restoring this thing, it's a High Sierra and it's loaded!!
Somewhat rare, has a super HD susoension,5th.wheel hitch in the bed, ball no shackle though.
The really cool thing about my truck is that it's like 110% original-all manuals papers nothing been replaced, and NO RUST.
At least the body that is, very minimal on underneath for being 28 years old.
What are you working on?☺
Click to expand...
a 1990 chevy silverado step side 4x4.
 
Cpl-Chronic

Cpl-Chronic

Member (SA)
floyd

floyd

Boomus Fidelis
i like my vehicles to sit high up because its easier to crawl under them and work lol. i bashed my ****ing hand when the spring i was trying to install slipped and i basically smacked into the wheel studs with the top of my hand that **** still hurts.
 
Ghettoboom767

Ghettoboom767

Member (SA)
I do to Floyd,I have huge P295-16's Goodyear Duratracks and now I need to get almost the best shocks I can get on here,starting with the fronts.
I want some coil over types that will give it a bit of some lift. I heard Efelbrock makes some good ones.
I don't have a lift kit so I just want some really good off road 4 wheel drive type shocks.

What I like about mine is its a manual 4 speed with the granny gear and I have posi-traction rear and limited slip from axle.
I have tuned it completely with a K&N air filter but now I have to turn the idol down as it's now idling a little high so it's somewhat hard to get it into reverse as it's just idling to high.
It really made a difference after I did a full complete tune up and that K&N air filter!😀😎
 
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