Low coolant light goes on and off and on and off

Howdy! My 1984 C20 Suburban 6.2 (used to be military vehicle)...low coolant light goes on and off and on and off with cold engine and even warm engine running. Radiator is full with 50/50 antifreeze. It does not have reservoir tank. I just bought it a few months ago. Own many trucks and suburban for 40 years but this one is my FIRST diesel. So what should I go and see if I can have it fixed? Thank you for your help.

Check and clean electrical connections first. They can become loose-fitting or corroded over time. If the sensor spade connector doesn't fit tight, slightly crimping the spade often cures it. If all the connections are good, the sensor is probably fouled with crud (common). Drain enough coolant to below the sensor, remove, clean and reinstall it.

Do yourself a favor and install an overflow/expansion reservoir. Use a universal tank mounted to the passenger side fender tub. Get one from Summit or Jegs. Without it, one trip to hot may be a game ender, or a loose, weak, or failed pressure cap will allow the coolant to remove itself, never to return.

Hi again...where can I find the low coolant sensor? Is it on radiator or overflow tank?

Probably not on the overflow tank, since you said it didn't have one. (It isn't)

It's in the radiator tank, passenger side, rear.

Like I said before...I'm new to diesel. However, I found that my Suburban has an overflow tank. It's way down in front of engine, that's why I did not notice it. Glad it has overflow tank. So the low coolant sensor is not on the overflow tank, right?

The sensor location is usually simple. It will be in the tank with the pressure cap. If the surge tank/reservoir has a pressure cap (later models), it will have the sensor. If the pressure cap is in the radiator tank, that's where you'll find the sensor. However, some models don't follow the rule, but I don't think the C/K's have ever had that issue. Look for a "regular" looking sensor with an electrical connector, or spades where a connector was. If on the radiator or surge tank, the low coolant sensor will be the only sensor there. This is not Diesel engine specific.

Here is where most 6.2L diesel low-coolant sensors are typically located; passenger side, below heater core return line and oil cooler return line:

https://farm8.staticflickr.com/7895/...26e5759c_b.jpg

Casey