VNL780 Coolant sensor and switch

The only way that i know is: On the surge tank you have the pressure cap on LH side you will see the air line (orange) come from the (APCS) solonoid and pressure sensor going to the surge tank on LH, install a plug on the hose to make sure your radiator never be pressurize by the APCS system and reconnect all harness and check the operation of the low coolant device.
Note: The APCS module broad cast the data link information for low coolant level with the float in the surge tank, also on that particular surge tank(VN) the low coolant level is part of the tank.
Hope this can help you.
Ben

 

Let me know if you need something else about that.
Ben

 

Suggestion, reconnect all harness at the module and make sure the air pressure getting out of the solonoid (RH)side of the radiator never can reach the surge tank.
Plug that hose.
Check with your cluster if you can read APCS system ?
If Yes, then drop 2-3 gallon of coolant and run the engine at idle for two minutes to see if your warning will work or safety shutdown (if programmed) will work.
If i remember correctly you have two level of warning:
LOW COOLANT and VERY LOW COOLANT
(only the Very Low Coolant will shut Down the engine)
If you have news about the By Pass Kit let me know the Part Number please. Thanks
Ben

 

Ben, I see your post here for years back. Are you still on this platform? I have an 07 VNL780 with D16. I have blown 3 radiators in the last three weeks. My oil cooler cover was just replaced in January 2022 (a few months ago), and that sealed up the pressure on my system. Have had numerous issues that lead to blowing the top out of 3 brand new radiators. Last month, a dealer in Clarksville IN removed the wiring harness from the APCS, and I too do not receive any low coolant warnings now, but the pressure buildup has cost me serious $$$$ with radiator replacements. Would love to hear back from you if you see this. Kevin Wilkins ([email protected])