1991 Dash Indicator Lamp - Low Level Sensor (Radiator Symbol)

On our '91 V12, the Coolant Low Level Sensor lamp has been on and off intermittently for years. Coolant is at proper levels in both tanks.

I’ve looked in the ROM for where this sensor is located to no avail. I cannot locate it in the mass of of wiring diagrams either.

There is a sensor wire at the side of the Driver Side tank(LHD), but removing that wire makes no difference at the dash lamp.

Any clues to where it’s located?


Assumingly, v12 has similar ‘advanced’ British technology on board like the rest of Jaguar range. Your dash light will go off when short to the ground. In 3.6 - coolant “sensor” is nothing different than metal pin located at specified height in the expansion tank. Try to drop the plug to the coolant tank itself and see if the light goes off. If not - you’re looking at frayed wires… Jaguar was doing plenty of savings on the sharp metal edges left in the final car

That is the sensor. It’s a simple piece of metal sticking into the tank thru a rubber grommet. It basically just detects coolant by putting a small electric current thru the coolant. No current = no coolant. There is an electronic device under the dash that takes that current, and tells the light to come on or not. That device can fail. There are rebuild instructions for that device on here somewhere.
Edit: Here’s the repair instructions.

Gents, Thank you. The link to that info is perfect. I’ll check deeper now that I have the info.


BTW, the coolant level electronic device is under the passenger dash on US model cars (LHD).

Yes I saw in the link you provided that John showed it’s there too. I’m going to get in there today to take a look.

I’m also working on a '72 E-Type and a '59 Corvette simultaneously. All 3 have been sold and I’m finishing up many issues in preparation for shipment overseas. The E-Type has been the most entertaining… er, ah, I mean frustrating. The XJS has given me some problems too but pretty much have that one ready.

When I get into the sensor issue on the XJS I’ll certainly keep this thread updated and will take some photos for future reference.

Thanks again you’ve been a great help.

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Couldn’t park my 90 XJS, same as yours, above my 61 corvette without covering vette. A few spots of oil and atf fluid would not be good.

Oh yeah, forgot about coolant level sensor. How clean is the reservoir? Had to clean mine thoroughly. Had similar problem.

David, Actually the XJS is quite dry underneath when a car is below it. The Corvette is good too, but after I cover the XJS underneath it I put a few cardboard sheets on it just in case. My 4 post has drip trays that cover the entire opening. When the E-Type is on it they’re mandatory. lol

Good idea…I’ll check the XJS reservoir too as it may have some junk in there preventing the sensor from getting a good reading.


Hope it does the job!