2001 Pontiac Grand Am Temp guage not reading/fan stays on

KNATCAL

MEMBER
2001 PONTIAC GRAND AM
6 CYL
FWD
AUTOMATIC
170,000 MILES

I have tested the Coolant temp sensor(which is about a year old) along with a new sensor, they both show similar readings as far as resistance both cold and sitting in hot water, readings were 5.4 ohms cold (not sure if thats the right spot for the decimal, it was set on 20 Ohms on the multimeter), and about 1.8 in hot water. Tested the plug for voltage, one side read ~4.8v. The fan stays on constantly, the temp guage is always at the bottom, which is 100 degrees. I'm at a loss here. It runs a bit rough sometimes, and takes forever to warm up with the fan on.

5 Replies

RASMATAZ

MECHANIC
75,992 POSTS

Hi knatcal, Welcome to 2carpros and TY for the donation

Below is a typical CTS values:

Fan constantly On -could be a fan relay sticking or the computer

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Wednesday, February 17th, 2010 AT 4:10 AM

KNATCAL

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4 POSTS

Okay, well it seems the values from the CTS are correct, I guess it was 5400 ohms to 1800, had the decimal in the wrong spot. I dont imagine its the fan relay unless by some chance it went out exactly when the guage stopped showing the temp. The fan should be controlled by the CTS via the computer correct? I'm guessing its not getting the reading from the CTS is not getting where its suppose to so its getting a false reading at the bottom of its range, assuming that it has an infinite resistance and it thinks its extremely cold? Or assumes that the sensor is malfunctioning and has no idea of the temp so it just plays it safe by constantly having the fan on? Any way I could test to see if there is a signal/voltage making it to the computer?

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Wednesday, February 17th, 2010 AT 8:18 AM

KNATCAL

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4 POSTS

Also I should mention, it is the cooling fan as well as the A/C fan that run constantly.

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Wednesday, February 17th, 2010 AT 8:20 AM

KNATCAL

MEMBER
4 POSTS

Well, after much digging on the internet, I have found others with grand am's that had the same issue, not resolved by the CTS, with multiple people reporting that it was their thermostat acting up and after replacement the problem no longer persisted. Will be giving that a try this evening.

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Wednesday, February 17th, 2010 AT 9:47 AM

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