Instrument cluster problem

Hi all , I have a problem with the instrument cluster on my 1989 4 litre XJ40 , due to a power draw i am using a battery isolator , connecting it back this morning it has done something to my instruments ,has done this before , changed the fuse for cluster before and has fixed the problem . this time no such luck , speedo , tach and all other gauges ( all needles pinged to the right )do not work , and the warning lights , battery , water temp and oil lights are all on . Have have changed all the fuses in both footwells and the ones in the centre console , no difference . Has anyone had this problem ? if so how do i fix this ? Are there any relays under the dash that can cause this ? I’m at a loss as what to do . Please help me .

mark does the car start? Have you removed the isolator and tested it ?

Hi , Car starts and runs fine , just the instruments and other things mention don’t work . The isolator is just a negative terminal isolator .

This is just a wild guess but maybe the ign on relay has stuck, don’t ask me where it is on an 88 no idea.
You could also try disconnecting the battery for a bit and seeing if that reboots things when you hook it up again.

larry , have tried disconnecting , doesn’t fix it . Will look for the relay and see if that does it . Thanks

Is the ECU in the red area or the green ? underneath all this wiring ? Confused .

Your 89 XJ6 Inst Cluster Problem? All needles pinned to right?
I have an 89 and it has the fluorescent digital display only tach and spedo have needles-pointers
You have all analog gauges and all are pinned??
How long have you had the pinned gauge problem??
If so sounds like a cluster failure… there is nothing in the car that would make all gauges PIN FULL…

When I got mine many display problems and all were cleared after opening the cluster and finding many a cracked and cold solder joints from years of heat cold cycles and weight of some parts stressing solder joints. After re-soldering all was well.
A little more info on your car and what seems odd to have analog gauges in 1989 XJ6 would help
Good luck
B

2tonejag , hi , the car is an 1989 , it is an early version of the 1990 , fitted with all the '90 equipment , hence the different dash . The problem with pinned to the right has only happened at the same time it blew the cluster fuse , changed fuse and everything else works except what i stated in the first post . So , yeah , off to the wreckers on the weekend , i know one that has the analog dash still in it .

Wrecker replacement if the wreckers know it to be good it may well work and not blow fuses. Would still be good idea to carefully open it up and while I have not seen the inside of analog dash I would assume there is a power board section somewhere with larger components and larger resistors. These are the parts that from their size and weigh and from their much higher power usage-more heat than other parts, develop stresses and cracked solder joints. May need a magnifier to see them. Yes just reflow the solder may need a touch of flux and or a bit of new flux core electrical solder. And one could examine the inside of the pinned gauge cluster and see if solder joints are bad.
Good luck.

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2tone , I’m not every electrically minded , what do i need to look out for to see a cracked or damaged solder ?

Any magnifier will do more power the better

Look for wires connected to circuit board as these are large and stress the board allot… large capacitors, large resistors… large transistors anything part bolted to (sometimes higher power transistors or TO220 cased, google it, voltage regulators) circuit board it it also has soldered connections. All IC integrated circuit leads… and if you find the cracks on a solder pad… they look like a minor to major crack ring encircling the solder pad where the parts lead pokes through the circuit board. And where you find these bad or questionable solder joints… look around the same area as there may be others. smaller parts rarely get stressed by mechanical jostling and or heat as smaller parts are designed not to experience large voltages or currents so minimal thermal stressing. Large parts can loose their solder connection from physical jostling and and more thermal stressing they may have to endure. Connection wires are high stress points and could be an issue with solder pads.
In summary, larger parts PC board wire connections kinda sums it up.
Good luck and happy hunting
B

Look at the circuit boards under a bright light preferably using a jewellers eye loop.

Look closely at everything that uses solder on the board. Sometimes the cracked area will be slightly discoloured giving you a clue but most are not. The solder break’s will show up as fine hairline cracks but if in doubt it’s best to re-flow them all and doesn’t take too long with a decent soldering iron. The most recent board I re-flowed was inside the ‘H’ box, the symptoms were the side and rear lights not coming on with the switch in sidelight position. I found 5 definite solder cracks on that board alone so besides curing the sidelight problem I also cured a long running problem I had with the interior lights ‘strobing’ whenever the door was left open.