Hi all, I'm new to this forum and hope someone can shed some light on my troubleshooting efforts. Here is my situation:

I acquired a 1987 XJS with 68,000 miles a month ago. It had been sitting in a closed garage for the past 15 years. I had a local shop that knows Jags do the brakes and get the fuel replaced, oil, etc. and had to put in a replacement distributor. Waiting for them to finish up, but now that she's running I see that the fuel, battery and temp gauges are dead.

I pulled the cluster and cleaned all of the contacts on the back foil, also pulled and inspected all fuses in both fuse blocks under the dash. The only gauge that works is the oil pressure. Tach functions and dash warning lights all function, so I suspect that there is trouble with the circuitry connecting to the gauges.

Since it has been sitting for 15 years, there is obvious corrosion on the electrical connections. Can anyone provide me some basic tips on troubleshooting these, like location of inline components, relays, values for readings? I have a good ohmmeter and can do basic stuff.

Any help is appreciated and thanks for your time.

 

A review of the wiring diagram might be a good starting place. From there, clarifying questions and answer can follow.


Click here:

http://www.captainjaguarscathouse.co...ec%20Guide.pdf


The first section (until about page 56) cover the XJ6 sedans. Scroll to about page 57 for the second section covering the XJS, then go to section 19.1 for instrumentation





Cheers
DD

 

Thanks Doug. I do have the wiring diagrams but they don't make much sense nor do they indicate where on the car the componenet is, nor is there any discussion on probable causes for specif failures like I hope to find in this forum.

They are a great help for understanding the architecture of the system though!

Bob

 

Well, since the tach, speedo, and oil pressure gauges are operative we know that the fuse is OK and voltage is making its way to the cluster....as all the gauges run off the same voltage supply. So, barring a problem with the printed circuit itself, I think "voltage supply" can be ruled out.

Lack of a solid, reliable ground to the cluster can play hell with the gauges. The easiest fix here is to run a new, redundant ground. The cluster has a metal bar running across the top (or is it bottom?). Run a wire from the bar to a known-good ground point under the dash. This, together with cleaning the circuit board contacts (which you've already done), often cures all ills with the gauges.

For the fuel and temp gauges you can unplug the sending unit wire, turn the key "on", and touch the wire to ground. The needle should pop to the top. If it does, you've proven that the meters themselves are OK and the wiring from the sending units to the meters is OK. That leaves faulty senders as the culprit. Both easily replaced.

The temp guage sender is on the RH water rail (single green/blue wire) and of course the fuel level sender is at the fuel tank (light green/orange wire)

If the needles do not pop up to the top then you have a wiring problem from the senders to the meter or faulty meters.

The volt meter operates simply on power and ground. Either the meter is dead or it isn;t grounded. This assumes, of course, that supply voltage really *is* making its way through the printed circuit to *all* of the meters.

Hope this helps a little

Cheers
DD

 

Great, thanks for the starting advice Doug. I'll do these tests as soon as she's back from the shop, early next week. I'll post my results here.

Bob
Kingston, WA