coolant light intermittently on: why?

[GentleGiant]

Hello good folks,

My 1984 CUCV pickup has the orange "low coolant" light coming on intermittently. It fades on and off and sometimes comes fully on. But then it will go off again, most of the time.

The coolant is not low.

Anybody know why?
Or whether there is something serious I should be worried about?
Or what to check first?

I have taken off the wire which goes to the radiator near the batteries - I assume this connects to a coolant level sensor. When its off, the light doesn't come on. The connection seems secure. I put it back on.

Other thoughts include that the coolant WAS low last year , but not seriously so. - loss was from a dripping freeze plug, which has been replaced. Also someone in the past has put plain water in the coolant system, so there is a little crud built up on the radiator fins (when I look down the filler hole I see a little buildup).

Any experience?

Thank you.
GentleGiant

 

[CenterMass762]

If I recall correctly, the light should turn on with the wire pulled off of the sensor and then turn off when the wire is grounded. If it does, the sensor is bad. If it doesn't, either the low coolant module under the dash is bad or you have a bad wire/corroded connection.

You might want to check the TM to verify that. It's been a long time since I've dealt with that.

 

[Barrman]

Follow the steps in the -20 as suggested above. The last few times any of mine did this just twisting the plug at the radiator cleared it up.

 

[dougco1]

Follow the steps in the -20 as suggested above. The last few times any of mine did this just twisting the plug at the radiator cleared it up.

Same with me, just messing with the plug fixed mine

 

[GentleGiant]

Thanks so much folks... I wiggled and twisted the wire at the radiator, and it has 99% fixed the "problem".

I appreciate your help - you gave me confidence to drive 3 hours yesterday and pick up a good used hay baler.

Eric

 

[87cr250r]

I have had issues with the copper/brass aftermarket radiators. The tube the sensor mounts in is too long and traps air. The plastic/aluminum radiators seem to work fine.