I appreciate yours and Dave’s help. It did not occur to me that I should have indicated that I was using a separate light I installed on the dash. The ones I use were from Radio Shack. They are 3/8” diameter and a very bright red. There was no missing that light. When the coolant got low the float would blink the light due to the sloshing of the coolant in the reservoir. When I fitted my son’s 240 with one twenty years ago I threatened to have the float switch control the radio power, because I knew that he would deem a nonfunctioning radio as a true emergency.

Those circuits have saved my bacon three times during our almost forty year history with old Volvos. A ruptured heater hose, a radiator hose and a failed water pump seal were brought to the driver’s attention before overheating occurred.

I can see having the float switch on the ground side (85) makes the most sense and that’s what I will do.

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Any twenty minute job is just a broken bolt away from a three day ordeal