My '87 XJ6 coolant temp gauge doesn't register. I jumped direct from sending unit to ground and nothing. When I turn the key there is a small movement in the gauge needle. All other gauges work. When I jump from the green wire at the sending unit to green wire in back of gauge it indicates open. When I check for voltage in the back of the gauge with the key on I get zero on both green wires and the blue/green wire. It seems to me there should be 12 volts at the back of the gauge with the key on. From the wiring diagram the green wire comes from the ignition switch through a fuse (I don't know which fuse but all fuses in the box under the dash check good) to the gauge and then from the gauge through the sending unit to ground. What is the blue/green wire? Is there an in line fuse I'm missing. Thanks for any help.

 

No inline fuse for the gauges.

The fuse you're looking for is #4 in the main (left) fuse box. But one fuse powers all the gauges so, since other gauges work, the fuse is OK

The green wire for "+" voltage to the gauges branches off and there are two sub-harnesses to the gauges. One of the might be a little loose? You'll have to remove the tach and/or speedo to to your hands in there. The tach and speedo are removed by pressing them inward firmly and turning. I can't remember which direction to turn them. Somehow I always forget

The green/blue wire goes from the gauge to the sending unit

While the tach and speedo are out check the two dashboard ground wires, one next to the tach and the other next to the speedo. You'll see 'em. The go to slide-on terminals on the dashboard metal backing plate



Cheers
DD

 

Thanks Doug. I've had the gauges out already. Will check the speedo and tach grounds, I didn't know about them. I'll also rejiggle the harnesses behind the dash to check for loose connection. Shouldn't there be 12v at the green wire with the key in the on position? Thanks again..........Jack.

 

Yes, 12v "+" with the key on, solid green wire. The green wire circuit is fundamentally operational; hopefully you'll find a loose connection that will explain why just temp gauge is getting the voltage

Cheers
DD

 

Well, success, sort of. I did pull a bonehead move when checking voltage and the green wire to the temp gauge is hot. When I check continuity between the sending unit and the blue/green wire behind the gauge I show open circuit, according to the wiring diagram it should be a straight connection and be low to no resistance. But when I had the speedo and tach out I could see the steering column was not secured correctly. There is a strap with two capture nuts holding it up and only one nut had a bolt through it and the strap was bent out of the way. So I got sidetracked fixing that. After that, I idled the engine awhile and the temp gauge showed some signs of life so I buttoned it back up and will call it fixed for now. My sending unit show 620 ohms resistance between the terminal and the securing nut, when I hit it with a heat gun it goes down pretty rapidly but the center part with the terminal is loose. It looks like a Beck/Arnley 201-1110 sending unit is a good replacement but I've (wow, there's a B25 parked at a small airport close to me and it just came in flying directly over my house at probably 250 feet, sounds incredible) read quite a few reviews about replacement sending units not being compatible, do you have any experience with this? Again Doug, thanks for your input and advice.

 

No experience with the 201-1110 so can't comment. The Jaguar number is DAC2583. Try Googling that and see what comes up.

I think the compatibility problems are related more to the older cars. Some vendors are selling a "modern" version of the sender as a replacement for darn near every Jag ever built....which is OK on the new-ish cars but not on the 50-60-70s Jags.

The B25s were louder than many other warbirds. The reason for this was explained to me but I can't remember. Anyhow, yes, magnificent noise

Cheers
DD