on my 1988 XJS v-12 I have no instrument cluster lights. fuse is good. Could all bulbs really be out? Also the Tach seems to be reading lower than it should. At cruise it says only 1000-1200 and idle sometimes almost nothing. When I really step on gas it goes up but not to where I THINK motor really is. Any ideas?

 

Regarding the lights... Check your rheostat under the steering column. Mine is "dodgy" and as I bought the car, I thought all bulbs were dead. But then it was just the knob being too fragile resulting in it turning off... Don't expect some bright lights though! They are about as dull as a 40w lightbulb is as bright enough for an entire football field!

 

Agreed on the rheostat.

Sometimes just exercising it will bring it back to life. Or, bypass it entirely.....that's what I do and the notoriously dim panel lights become a tad bit brighter. But not so bright that you'd ever feel the need to dim them, trust me

The tach might be faulty in some way....or suffering from poor connections and/or a bad ground. Or perhaps the mechanical portion of the meter needs a very tiny drop of light oil?

Remove the cluster, clean all the contacts points on the (fragile) printed circuit board and the contacts in the two harness connectors as well. Also add a redundant ground to the cluster. These steps often make quite a difference in gauge readings and panel lights.

Cheers
DD

 

I've still got to sort mine out with variable bulbs (all new), intermittent or non -functioning speedo and a rev counter that only goes up to 2000rpm.
One thing I have been told to check is the condition of the multi plug connectors behind the dash.
Might get round to it one day.
Saw a documentary on the making of the F Type last night; the wiring loom is so big that they have to put it in a bag and heat it in an oven to make it flexible enough to fit in the bare car.
Fat chance of trying to sort out any wiring problems on one of those in 20 years time.

 

Ok I got the cluster out tonight and honestly found next to no corrosion. Below are some pictures. I'd like to replace all the bulbs with LED green bulbs as a lot of folks say they actually make the gauges readable at night.
All the posts I've seen are garbled and no clear list of what bulbs to use is all I've seen. The kit from v12 seemed nice but that website doesn't exist anymore? Can someone let me know what exact part numbers are for the green bulbs for intrument lights and what the clear bulbs are for the warning lights (id be ok with leaving the warning bulbs stock as they are plenty bright. I'd like to even remove the seat belt warning light...will that make the yellow bulb out light go on if I either leave bulb out completely or install a burned out bulb there?
Before I removed cluster I verified the 5A fuse is indeed ok and I operated the dimmer switch back and forth several times and still no lights. Upon inspection of the bulbs (after I got cluster out obviously) none appeared burnt out. Any other ideas?
Where exactly should I install extra ground wire to in the back of gauge cluster? I hope it's as simple as a extra ground but as clean as this thing was I'm skeptical.

 

Use some contact cleaner on the dimmer. That worked with mine.
Use a meter and check voltage in and out of dimmer.

 

That long steel bit along the top of the cluster, which you can clearly see in the second pic, to which a couple of copper pieces of flexible are bolted, is the main earth strap. earthing this to the car frame is a good plan. But CAREFULLY undo those tiny copper pieces that bolt to it and lean them up. Any corrosion there will prevent proper earthing too. You could also CAREFULLY undo each tiny screw, one at a time, under each contact from the flexible and clean there too. Each tiny screw actually is a contact into the instrument itself and hardly any corrosion is needed to affect the gauge performance.
As to the bulbs, unclick one of the black bulb holders and take it to a store and find something that will fit, I suggest. Remember that LEDs are polarity sensitive, so trace the copper from each one to see which is earth and which is live, and then test the bulbs so you put them in the right way.
Greg

 

With the instrument cluster removed...I cleaned all the contacts with contact cleaner and then applied a contact sealer spray on to help keep from future oxidation. I loosened the screws and re set each one. It was very clean already and little oxidation found but since it was out I went ahead and cleaned.
I tested all the bulbs for the warning lights. I found one bad bulb. I reinstalled it in the seat belt warning slot. With this bulb being bad will that make any "bulb out" lights come on???
I believe warning bulbs could be replaced with type "37" bulbs. Correct?
I replaced the 5 instrument cluster bulbs with white LED bulbs. See pics below for exactly what I used. I got these at Pep Boys. $12.99 for pack of two (used on tach and speedo). $7.99 for pack of two used on the remaining 3. (I have one extra as they are only sold in packs of two. My idea is the center gauges and lower speedo bulb need only the 1 led bulbs and the speedo and tach I used the 5 led bulbs. These bulbs came with a neat little 12v battery source to let you see the brightness before you buy. I used that device to test the bulbs and to test the flexible circuit board also. Worked great! Really handy they came with the little 12v device. I'll save those for future checks on lights etc. I have the cluster all ready to reinstall except I am going to add two extra grounds. (There's two open holes in the ground metal strap so I'll make two ground wires tomorrow before I reinstall).
I also dropped lower dash and found one plug was off the dimmer switch. Sooooo that is probably the reason why the dash lights didn't work anyway. I'm going to spray some cleaner on Reostat anyway and hope all is well when I reinstall instrument cluster.





I used three of these



I used two of these one on speedo one on tachometer





I had to trim a little off the black edge of the three single ledsfor them to fit in holes



I had to open the top and bottom of tach and speedo holes with a hobby knife for the bulbs to fit



With the 12v battery deal that came with the LEDS I was able to see if each bulb worked. You can see where the red wire and black wire goes so you can test.

 

Ok I added two new 14 gauge grounds. And reinstalled the cluster (plugged in but not all screwed in). I go to turn on lights and only the trip computer back lights, radio back lights and shifter selector light up. I started it and no tach but engine gauges work.
I tried cleaning reostat and nothing changed. I then too a paper clip and bypassed reostat completely. The red/blue wire in picture below that goes to reparations has 12v. I used a paper clip to connect that plug to the other two and noticed zero change. Even with the reostat out and the red/blue wire going to nothing the trip computer and radio and shifter selector still work.

There is a red wire disconnected on left side above fuse panel. It's not long enough to go to light switch. And there is also a round plug with two wires that are red and yellow discounted. See pics below. ANY idea what these go to???

I tested the gauge cluster and it did light up with all bulbs installed when it was out of car. (I used the 12v power supply that came with the new leds.

Any ideas what to do now??? Is there a relay or something im missing?



The single red/white was the one disconnected before. I guess it's connected where it goes now???



Any idea what their goes to???



Any idea what this goes to?



That is the plug that is disconnected. It's a red wire



Just left of the gold Phillips crew and I'm using a screw driver to point to it



These are the wires going to reostat. The red/blue has 12v. With it connected to reostat or wired directly to either of the other two plugs nothing changed. The 5a fuse is good.

 

One other thing...the fog lights never come on either. Not sure if that could be related?

 

I *think* that vacant round connector might go to the fog lamps. Is there a mate to it lurking about?

Or....some of the XJS foglamp circuits used a jumper plug.

I don't have my XJS diagrams at hand to check. Others will chime in

Cheers
DD

 

The lighting switch feeds Main fuse panel #7. This feeds the rheostat which feeds the instrument panel illumination, center switches ill, and fiber optic ill.

Look in the xj6 sections tips post to find the S57 document. XJS wiring begins on page 57.

 

My '88 also lacks fog lamps and has lazy gauge lights. I've considered cleaning or tinkering with the rheostat as well, but haven't gotten around to it (I've replaced all the lights and cleaned the contacts on the cluster).

My fog lamps are disabled because a relay, straight back from the lighting knob (deep in the dash) has been removed and the wires leading to it are fried. I suspect the two items are related. You'll have to let us know what you find in the dash when you go to conquer your fog light problem.

 

Panel lights: as some dash lights are coming on, the switch etc is OK. I suggest you check the incoming 12 feed to the cluster plug to see if it is getting 12 v when the lights are on. If you do not have a diagram. CAREFULLY trace the copper track back from the known 12v side of an LED bulb to the point on the cluster where the plug goes in. I have a feeling, no more, that it is the smaller of the two plugs that has the feed, but I could easily be wrong. Once found, test the actual plug copper piece that fits the track position you have identified for 12v when the lights are on. If no volts there, the problem is the wire between the switch and the cluster plug. It is also quite possible that the plug copper piece is not actually contacting the flexible circuit board when plugged in. If you find there is 12 v at the plug, rig up a wire from the plug to the copper trace and see then if the lights work.


Tach: if the tack is not working, that probably has nothing to do with the panel lights. Again, trace the tach signal feed track to the copper plug. I am not sure how to test for the tach signal, so ask someone in a specific post to tell you; warrjon will know for sure.

If no signal, and IF you have Lucas ignition, it is the white with blue trace wire that comes out of the ignition amp that goes into the loom to the tach, via a bullet connector near the coil top. This is worth checking for continuity anyway.
Greg

 

Ok so I have confirmed 12 volts at the small plug connector that plugs into the rear of the dash...it's the lower row, third one over on the plug that gets 12v when lights are turned on. (Should beable to see in one of my other pics I used a battery pack of 12v attached to this point on the flexible printed circuit board to test my lights when I had dash out and was replacing bulbs)

It must just not be making good contact. I'll try to pry the copper piece in the plug up a bit and try again.

On the round plug. It does have 12v when the fog lights are turned on. Any idea where the other end (the end coming from the fog lights) might be hiding? I can not find it anywhere.