Adding Warning Lights

#1

I am looking to add some warning lights to warn for low oil pressure, High oil temp or high water temp and I have a few questions.

  1. What are good values to use to trigger the lights?
    Oil Pressure: I understand that the stock low oil pressure light is on around 7psi. (.5 bar) This seems a little low. I was thinking around 15 psi or so. Thoughts?
    Oil Temp: 270 degrees F as it is a common value given in the warning lights.
    Water Temp: 230 degrees F standard value given on the warning lights.

I am looking at using the Longacre warning lights and those seem to be the values.

  1. Where can I mount the 3/8 or ½ NPT temp switches? The pressure is easy as it is 1/8” but the temp switches need a bigger hole.

Thanks,

Michael
#36
Great Lakes Region

#2

For reference the highest my oil has ever been is 222 and that was with non synthetic oil. With redline it doesn’t get over 210. Water temp is usually under 200 but I did notice it was at 210 when I was behind Jeremy for a long time. Hope that helps some, no idea on the pressure I think mine is set to 10psi. I wouldn’t notice the warning lights though even if they were going off.

#3

What one would like to have as an oil pressure warning light is one referenced to rpm. Tripping the light when the pressure falls below 10psi/1000rpm would be more useful than something that trips a at a specific pressure.

I’m with Elephant4 on the oil temp. M20’s don’t have oil temperature problems unless something else is really wrong. In which case there will likely be other more obvious symptoms.

The stock thermostat housing can be modified to accept an additional sensor. Or you can get a new housing from a dealer which will come with two additional tapped holes. Once of which can be used to mount an overtemp switch. Personally, I’d rather have a thermoswitch on the head itself but I don’t know of a good way to accomplish that easily. If I was going to do that, 225-230F would seem to be a good limit.