My temp gauge hasn’t been hooked up since I got my ’83 Jimmy and I just put a new sending unit in and as soon as I turn the key on the gauge spikes all the way to high (completely out of the temp range). I’m not real good with electrical and gauges, wondering if someone can point me in the right direction here? What am I missing?
CK5
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Temp Gauge help
- Thread starter XRO
- Start date
The sending unit is basically a variable ground--the hotter the coolant gets,the less resistance to ground the sending unit has,and it makes the gauge read higher ...if you unplugged the sender wire and grounded it,(with the ignition "on") ,the gauge will peg the needle all the way to "hot" ...so I'd assume the wire is pinched somewhere and grounded out..especially if it pegs the needle with the wire not plugged onto the sending unit..
There are different sending units for vehicles with an idiot light VS a gauge--so make sure you have the correct one...if you used a sending unit for an idiot light with a gauge it could cause your symptoms..
There are different sending units for vehicles with an idiot light VS a gauge--so make sure you have the correct one...if you used a sending unit for an idiot light with a gauge it could cause your symptoms..
digitalepiphany
1/2 ton status
Any idea what could cause it not to work at all? There was just a plug put in the side of the block when I got my Blazer, so I put in a new sending unit and hooked it up. The gauge does absolutely nothing.
Diesel4me, my gauge is doing something similar I can crank it up gauge is fine then all sudden the gauges goes all way to 20 after like on a clock but coolant is fine with infra red gun. I did unplugged the sender wire and grounded it,(with the ignition "on") ,the gauge will peg the needle all the way to "hot". But what would cause it to go crazy whenever it wants to while driving? I have tried 2 sensors in block now. Any help would be nice cause gauge going crazy get's old!!!!
XRO,I would say its probably the wrong sending unit for your application...reading up on google I found that different year GM's used sensors for temp gauges that have different resistances at certain temps..so not only can one for an idiot light not work a gauge right,so can the "wrong" one for a different year truck..
Brans87,if your gauge works fine,then decides to "peg out" past full,I'd guess the wire going to the sending unit is touching ground somewhere,most likely against the exhaust manifold or headers seeing it runs right by it..
Digitalepiphany--not working at all--first try turning the key "on" and grounding the wire to the sending unit--if the gauge doesn't read all the way to "hot" it could be the gauge is not getting 12V to it from the ignition switch,or the gauge has smoked and is no longer working..
I'll attempt to post this link to 73-87 Chevy trucks website,where I read the info on gauge troubleshooting..has a good text on how to test them and how to make use of resistors and a multi-meter to test the gauges and sending units,and the specs for the right resistance for certain years..
Brans87,if your gauge works fine,then decides to "peg out" past full,I'd guess the wire going to the sending unit is touching ground somewhere,most likely against the exhaust manifold or headers seeing it runs right by it..
Digitalepiphany--not working at all--first try turning the key "on" and grounding the wire to the sending unit--if the gauge doesn't read all the way to "hot" it could be the gauge is not getting 12V to it from the ignition switch,or the gauge has smoked and is no longer working..
I'll attempt to post this link to 73-87 Chevy trucks website,where I read the info on gauge troubleshooting..has a good text on how to test them and how to make use of resistors and a multi-meter to test the gauges and sending units,and the specs for the right resistance for certain years..
digitalepiphany
1/2 ton status
Thanks man.
Let me know how you make out...
Dummy light will be open/close, no resistance ratings to speak of. The temp *sender* (a sensor is for a computer controlled app only, as in CTS) for this vintage is all the same, so if you do need to replace it, or make sure you get the right one, it would need to be from the '79 up trucks.
FWIW the temp sender specs are the same long after 1990, as the integral wire senders from the later trucks (way better than the nail head one used on our trucks) work wiht out guages as well.
FWIW the temp sender specs are the same long after 1990, as the integral wire senders from the later trucks (way better than the nail head one used on our trucks) work wiht out guages as well.
digitalepiphany
1/2 ton status
diesel4me - I read through the article you posted, but am still unsure how to ground the wire to the sending unit. The temp sending unit screws into the side of the block, and the wires from the gauge plug into it. Which wire is the ground, and how do I ground it?
"Wires"? There is only one wire for a gauge sending unit. If there is more than one, it's not the right piece.
Regardless of year, if yours doesn't look like this, it's wrong, or you are dealing with some other piece unrelated to the gauge: http://www.ebay.com/itm/1960-1972-B...Parts_Accessories&hash=item27df7470f1&vxp=mtr note the "nail head" for the connector.
Regardless of year, if yours doesn't look like this, it's wrong, or you are dealing with some other piece unrelated to the gauge: http://www.ebay.com/itm/1960-1972-B...Parts_Accessories&hash=item27df7470f1&vxp=mtr note the "nail head" for the connector.
digitalepiphany
1/2 ton status
Here's mine. I guess it does only have one wire, but I'm still unsure how to ground it.
What I do is on the sending units with the "button" type connector,is use a tack or nail with a head the right size to fit on the wire connector ,then use a wire with two alligator clamps to hook the nail to a good ground--any clean metal part or the negative battery post works..then get in the truck,turn the ignition on,and see if the gauge needle buries all the way to "H"...if it does,the gauge works and the wiring is OK..
digitalepiphany
1/2 ton status
Thanks. I'll give that a shot some time in the next couple days.
digitalepiphany
1/2 ton status
Changed the fuse and grounded the wire. Didn't work. Does that mean the gauge needs to be replaced? Or could it also be something else?
The gauge could be junk,or the gauge may not be getting 12V from the ignition feed wire--or the wire you grounded might be broken somewhere ,so its not really grounding.....
It could be poor connections at the printed circuit foil on the back of the dash that feeds current to the gauges too...you'll have to pull the dash cluster out to check for voltage at the terminal that gets "fed" 12V from the ignition to the gauge..and look at the printed curcuit and see if its all intact,with no burnt spots or breaks in the copper strips on it..
I like to go with aftermarket gauges when the originals fail--for temparature and oil pressure mechanical ones are more accurate and less likely to fail than electrical ones..
It could be poor connections at the printed circuit foil on the back of the dash that feeds current to the gauges too...you'll have to pull the dash cluster out to check for voltage at the terminal that gets "fed" 12V from the ignition to the gauge..and look at the printed curcuit and see if its all intact,with no burnt spots or breaks in the copper strips on it..
I like to go with aftermarket gauges when the originals fail--for temparature and oil pressure mechanical ones are more accurate and less likely to fail than electrical ones..
digitalepiphany
1/2 ton status
Thanks. I'm installing some after-market temp and oil pressure gauges under the dash this weekend. I'll get to the dash eventually.
Other than being hard to read, there is nothing wrong with the factory gauges, other than how GM connected them to the truck. The printed circuit "board" (really a flexy plastic laminated film thingy) attached to a plastic connector, and the bulb/gauge terminals connected similarly, and they tend to fail.
Only real solution IMO is to hard wire all the guages, but that is a lot of work.
Only real solution IMO is to hard wire all the guages, but that is a lot of work.
digitalepiphany
1/2 ton status
I know LMC sells those circuit boards. I may be able to take a look at mine tomorrow if I have time to pull the dash bezel to get to the radio, and assuming it's not too much of a PITA to get to the circuit board.
