Coolant Gauge Malfunction

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.

Rawg

Newbie
Joined
Mar 23, 2022
Messages
3
Reaction score
1
Location
43081
1995 GMC C1500 5.7 TBI
I replaced the head coolant temperature sensor. Now the coolant gauge is reading over 260. It was operating normally before I replaced the sensor - it would typically read around 170-190. I made sure to use the proper sensor that has only one terminal and a one terminal connector.
 
Last edited:

Rawg

Newbie
Joined
Mar 23, 2022
Messages
3
Reaction score
1
Location
43081
I tried unplugging the head sensor pigtail (1 terminal) from the head sensor, leaving the intake sensor pigtail connected to the intake sensor. The gauge goes back to normal.
 
Last edited:

tpass

I'm Awesome
Joined
Apr 8, 2021
Messages
279
Reaction score
467
Location
Mass
These aftermarket sensors are hit or miss on quality if you don't buy AC delco, what brand is it? Why did you swap if it was working previously? Does the gauge read the correct cold temp?

you can easily test them with a multimeter and some hot water in a cup... put your meter on ohms and dip the sensor in hot water. Red lead on the terminal and black lead on the metal body. The hotter the temperature, the lower the ohm reading, compare the two sensors against each other.

I don't know what the correct ohm readings should be on a sensor for your truck, but that would be key to know to verify if you have the correct sensor.

ETA: the intake sensor is for the ECM, The sensor in the head is for the gauge and they are separate systems.
 

Rawg

Newbie
Joined
Mar 23, 2022
Messages
3
Reaction score
1
Location
43081
These aftermarket sensors are hit or miss on quality if you don't buy AC delco, what brand is it? Why did you swap if it was working previously? Does the gauge read the correct cold temp?

you can easily test them with a multimeter and some hot water in a cup... put your meter on ohms and dip the sensor in hot water. Red lead on the terminal and black lead on the metal body. The hotter the temperature, the lower the ohm reading, compare the two sensors against each other.

I don't know what the correct ohm readings should be on a sensor for your truck, but that would be key to know to verify if you have the correct sensor.

ETA: the intake sensor is for the ECM, The sensor in the head is for the gauge and they are separate systems.
Thanks for the reply. I ended up exchanging the after market for an AC Delco and it fixed the issue. I have been trying to resolve a rich fuel mixture problem. It is a not so well maintained truck that I inherited.
 

tpass

I'm Awesome
Joined
Apr 8, 2021
Messages
279
Reaction score
467
Location
Mass
so the rich fuel issue could possibly be the intake sensor, if it isn't sensing a warm motor. you could test that the same way, or just swap it with a new acdelco.
 
Top