No power at temp gauge

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

7

76burb

Junior Member
Joined
Aug 10, 2024
Posts
14
Reaction score
3
Location
texas
First Name
matt
Truck Year
1976
Truck Model
suburban k20
Engine Size
400
76 3/4 ton suburban. All gauges work except the temp gauge. Replaced the sending unit, gauge still won't move. When I ground the sensor wire the gauge pegs past full.

I pulled the gauge and used a multimeter to test the receptacles where the gauge plugs into the cluster. Driver side plug should be 12v key power and top should be ground. I get -.02 on my multimeter when I test those. When I test passenger post(sending unit) and ground I get 11.6v.

What do I need to do to get power to the gauge. The key was on when testing.
 
D

dd1990

Member
Joined
Nov 3, 2023
Posts
36
Reaction score
67
Location
Ventura CA
First Name
David
Truck Year
1990
Truck Model
Suburban 1500
Engine Size
350
Sounds like wire going to senidng unit is cut or gauge cluster printed circuit is messed up. I would look up the temp wire on the 18 pin and see if you get any continuity
 
7

76burb

Junior Member
Joined
Aug 10, 2024
Posts
14
Reaction score
3
Location
texas
First Name
matt
Truck Year
1976
Truck Model
suburban k20
Engine Size
400
Sending unit wire seems to be good. What is the 18pin?
When I ground the sending unit wire to battery gauge pegs full. If I manually move the needle to the right and then turn the key on the needle goes back to cold.
 
R

Ricko1966

Full Access Member
Joined
Apr 11, 2017
Posts
5,385
Reaction score
8,589
Location
kansas
First Name
Rick
Truck Year
1975
Truck Model
c20
Engine Size
350
If you ground it and it pegs,then your getting power,you are not getting a controlled ground. Check continuity on wires from sender to gauge and sender to head.
 
Last edited:
R

Ricko1966

Full Access Member
Joined
Apr 11, 2017
Posts
5,385
Reaction score
8,589
Location
kansas
First Name
Rick
Truck Year
1975
Truck Model
c20
Engine Size
350
Check continuity from the sender terminal to head on the sender with wire disconnected. Check hot and cold see what readings if any you get.
 
75gmck25

75gmck25

Full Access Member
Joined
Oct 13, 2016
Posts
2,252
Reaction score
2,190
Location
Northern Virginia
First Name
Bruce
Truck Year
1975
Truck Model
K25 Camper Special TH350 NP203
Engine Size
5.7
Did you use Teflon tape on the sending unit threads? That can prevent getting a good ground to the head. Check resistance between the sending unit body and the engine and it should be zero.
 
7

76burb

Junior Member
Joined
Aug 10, 2024
Posts
14
Reaction score
3
Location
texas
First Name
matt
Truck Year
1976
Truck Model
suburban k20
Engine Size
400
Update-- I did find a small cut in the green wire. I replaced that section of wire and still have the same issue. Temp gauge stuck on cold. If I remove the gauge and move the needle to hot then replug the gauge back in it flips back to cold immediately. I have tried another gauge and that one does the same thing.

I also put my testers on both ends of my old sending unit while it was out of the block and got infinite resistance or the 1 on the far left of screen.

when I put the tester on the installed sending unit and then the other to the engine I got the same 1 on the far left side of the multimeter which I think means infinite resistance
 
G

gmbellew

Full Access Member
Joined
May 27, 2018
Posts
1,211
Reaction score
1,278
Location
Kansas city
First Name
glen
Truck Year
1990
Truck Model
suburban 1500
Engine Size
350
infinite resistance means it is open and has no continuity, right? sounds like a bad sending unit?
 
R

Ricko1966

Full Access Member
Joined
Apr 11, 2017
Posts
5,385
Reaction score
8,589
Location
kansas
First Name
Rick
Truck Year
1975
Truck Model
c20
Engine Size
350
76burb said:
Update-- I did find a small cut in the green wire. I replaced that section of wire and still have the same issue. Temp gauge stuck on cold. If I remove the gauge and move the needle to hot then replug the gauge back in it flips back to cold immediately. I have tried another gauge and that one does the same thing.

I also put my testers on both ends of my old sending unit while it was out of the block and got infinite resistance or the 1 on the far left of screen.

when I put the tester on the installed sending unit and then the other to the engine I got the same 1 on the far left side of the multimeter which I think means infinite resistance
Click to expand...
Did you check either of them hot? Did you check continuity sender to head?
 
7

76burb

Junior Member
Joined
Aug 10, 2024
Posts
14
Reaction score
3
Location
texas
First Name
matt
Truck Year
1976
Truck Model
suburban k20
Engine Size
400
cold and out of the truck the sending unit tests about 600 ohms. I installed the sending unit and let the engine run for a bit to get hot and then tested the sending unit and grounded to a bolt on the ac bracket and got like 200ohms

Gauge still reads just above cold. tried a different used gauge and it reads the same. teflon tape removed from the new sender

I have also tested the resistors on the back of both gauges and they read roughly 85 and 95 ohms
 
Last edited:
R

Ricko1966

Full Access Member
Joined
Apr 11, 2017
Posts
5,385
Reaction score
8,589
Location
kansas
First Name
Rick
Truck Year
1975
Truck Model
c20
Engine Size
350
76burb said:
cold and out of the truck the sending unit tests about 600 ohms. I installed the sending unit and let the engine run for a bit to get hot and then tested the sending unit and grounded to a bolt on the ac bracket and got like 200ohms

Gauge still reads just above cold. tried a different used gauge and it reads the same. teflon tape removed from the new sender

I have also tested the resistors on the back of both gauges and they read roughly 85 and 95 ohms
Click to expand...
Double check me but I think 74-78 cold reading should be 350 ohms. I'm thinking you have the wrong sender to the best of my knowledge there are 3 and all 3 are different resistance.
 
7

76burb

Junior Member
Joined
Aug 10, 2024
Posts
14
Reaction score
3
Location
texas
First Name
matt
Truck Year
1976
Truck Model
suburban k20
Engine Size
400
Ive got the sender with the round terminal that fits the Packard connector on the sender wire. I thought the later senders had a spade connector.
 
R

Ricko1966

Full Access Member
Joined
Apr 11, 2017
Posts
5,385
Reaction score
8,589
Location
kansas
First Name
Rick
Truck Year
1975
Truck Model
c20
Engine Size
350
Resistance
 

Attachments

  • Screenshot_2024-09-12_175354.jpg
    Screenshot_2024-09-12_175354.jpg
    73 KB · Views: 31
You must log in or register to reply here.

Similar threads

K
Temp gauge not working
Replies
1
Views
504
76burb
7
Jtobe81
Fuel Gauge past full
Replies
11
Views
651
Jtobe81
Jtobe81
80C20Jon
Temp gauge says overheating but the truck is 195°
Replies
7
Views
683
80C20Jon
80C20Jon
Hamgrease
Oil pressure gauge problem
Replies
12
Views
1K
duece1951
duece1951
brooksman9
No power at Temperature sensor
Replies
10
Views
1K
brooksman9
brooksman9

Latest posts

Forum statistics

Threads
44,082
Posts
949,024
Members
36,160
Latest member
iandrake
Top