Temperature gauge random dig, false positive

THESULLYMAN

MEMBER
1997 OLDSMOBILE 88
3.8L
V6
2WD
AUTOMATIC
50,000 MILES

Okay, so I have had lots of issues since a multi-state trip (years ago) which caused a major meltdown if you will. A few issues have been solved here so thank you!

The engine temperature gauge (I assume the name) on the cluster constantly digs. This happens regardless if the car has just started.

The car will go ten minutes and it randomly starts digging in a very staccato fashion. Sometimes it is not immediate and will go twenty to thirty minutes and sometimes not at all.

I have replaced the coolant temperature sensor with no resolution of the issue.

I am wondering if it is a false positive or if it is an actual issue resulting from the previous major issues. (Below they are described)

Latest: The head gasket had a coolant leak which cause the engine to lock up, had a friend (mechanic) help out and we replaced properly and cleared all out coolant found as well.

Earlier:
• Oil sender replaced due to a heater caused hole in sender causing leak.
• Radiator (leaks) and fan replacement (stopped working).

1 Reply

ASEMASTER6371

MECHANIC
52,797 POSTS

Good morning.

You need to check the gauge itself to be sure it was working properly. Once that is determined, then you need to move on to the system itself.

To verify the gauge, I attached the description and checks for you.

Roy

The coolant temperature gauge is also operated by two coils. Battery voltage is applied to both coils. One is grounded directly and the other is grounded through the Engine Coolant Temperature (ECT) sensor. This has 55 ohms resistance at 127°C (260°F) and its resistance becomes greater at low temperatures. It is approximately 1400 ohms at 38°C (100°F). This causes the current through the sensor and one coil to increase as the coolant temperature increases. This moves the pointer.