Heya,

I really can’t make sense of a few electrical gremlins and would appreciate hearing from anyone who may have had experience with the following.

82 Xj6 Daimler s3 4.2

speedo did bounce around but the ODO seemed to turn over … now the entire thing seems to have stopped working halfway through a wee drive today. The needle went completely dead … UNTIL, I decided to cycle the headlights… the needle for the speedo started to work again. Turn the lights off - it all goes dead again. The indicators all work and flash externally, however - on the dash… they show intermittently … and guess what, when I apply an indicator , the bloody speedo climbs into life again until the turn is complete and everything goes dead again.

oil gauge reading hard right, heater / blower also doesn’t want to climb into life (aside from a small groan when you first turn it on - picking a stuck blower?)

anyway - the above just simply doesn’t make sense to me… there’s is no logic? All fuses operational.. and the weird thing is sometimes the aforementioned work fine for a moment , then become the hot mess as described above.

any ideas welcome!!

 

just guessing but troubleshooting requires guesses:

1) speedo transducer at transmission is responsible for speedo gauge. Checking the wiring to it is a good idea and an intermittent transducer is reason to replace it.

2) there are two electrical Posts at the firewall, one driver side, one at passenger side. Wires are bolted to them, they have a rubber boot covering the wiring bundle and nut. Disconnect the Battery, remove nut and clean the wiring ring terminals with a wire brush. Also clean the post shiny. Do this on both Posts.

3) the issue with the Turn Signals flashing then not at the speedo and tachometer is a mystery to me, my 1984 does it too, when the Headlights switch is in any ON position, can't help with that. I know there is a Diode. in the wiring harness to each gauge, I have replaced the Diodes and it keeps doing it. So it cannot be the Diodes.

 

sounds like an earth problem on the dash, also possible bulb failure unit, blower motors separate item, i can send you an extract schematic of the motors. you don't need a bulb to be blown for the failure units to be faulty.......

 

Nothing to add that's Jaguar-specific, but compromised grounding points on anything, especially motor vehicles, can cause all kinds of weird stuff, including the intermittent part.

Clean ALL grounds - that means the body panel, chassis, or whatever the wire(s) is connected to, as well as any and all fasteners involved - bolts, washers and nuts. With the wires, same deal - all ring terminals, bullet (Lucar) and spade connectors that might be on that wire. Make sure the bullet and spade terminals are tight. Basically, make sure EVERYTHING is clean, dry and tight. I assume as a later car it will have block connectors, with these contact cleaner and connect/disconnect a few times should clean them up.

Obviously you should check the + (hot) side as well, but start with grounds. Small brass wire brushes and some contact cleaner will work well. Spade and bullet connections can be carefully crimped if loose.

...hey, if there's no change, at least some preventative maintenance has been done.

Wiring gremlins are the worst ime, hope you find 'em...Good luck!