coolant switch?

[dependable]

The green wire on the IP is cold start timing advance, the other green wire connected to it is cold start idle boost solenoid. The one on the radiator is the low coolant lamp. Pretty sure they are un related. Sounds like you may have had air in fuel from sitting, just a guess.

 

[19CUCV85]

you may be correct. after a fluid change in 40 degree weather started like a champ. No issues with test drive. maybe just cleaning the contacts afforded the "fix" I was thinking more along the lines of a failsafe where as if the coolant is low the vehicle will not start or be problematic. Just thinking out loud. Not that I could find anything that would substantiate that.

 

[Barrman]

No, the green cold idle advance solenoid and the fast idle solenoid wire at the IP is not in any way connected to the radiator low coolant sensor/light.

 

[spectre6000]

Here's the geek answer:

The low coolant module card consists of essentially a harmonic oscillator circuit (the big 14 pin chip) and a circuit to check the return signal (the high tolerance 100K resistor). The harmonic oscillator sends a signal to the capacitive sensor at the radiator at a high frequency (~10K Hertz). The sensor tests the capacitance of the medium in which it is immersed (water/coolant or air) and sends the signal back to the LCM card. The signal then returns and is run through the checker circuit, and if it reads out of bounds it throws the light to ground.

To put this reply into context, I have the schematic for the LCM board on my coffee table with a LCM sitting on top of it after having been relieved of its diodes for testing (hopefully we get the rig built this weekend and get them fully identified). I intend to reproduce these in the very near future, and will be entering the prototyping phase in the next week or so. It's been slow going of late because getting my truck running and suitable for use as a DD, but once I get the cooling system purged of air, that's all but done and electrical becomes top priority.

 

[AECS]

Correct, that is one way to get a possible answer, but there are many ways that this circuit
could be implemented, and I was curious about the one in the CUCV, not the modern day vehicle.

In particular, is the device an actual switch, or is it just enabling a circuit path to the water
and back to the grounded block. Note, the radiator itself is not grounded and there is only one lead to the device.

I was just curious as to the specific methodology of this device.
Bruce

I am pretty sure the radiator is grounded. Not directly, but in my effort to stop the electrolysis issue I was having I tried everything I could to make sure it was not grounded, chased my tail around and around.

Then it dawned on me, impossible to isolate the radiator, there are 2 metal transmission cooler lines attached between it and the transmission case which is grounded. The cooler lines ground the radiator even with the rubber feet top and bottom.

 

[dependable]

Then it dawned on me, impossible to isolate the radiator, there are 2 metal transmission cooler lines attached between it and the transmission case which is grounded. The cooler lines ground the radiator even with the rubber feet top and bottom.

If you wanted to, you could break the ground path of coolant lines with a section of fuel or hydraulic line. Double up the clamps for security. Not sure how this would pertain to topic on this thread, but have used fuel line as a repair piece for broken lines in past with no problems.