NOTE: MY stands for model year, icydk.

I found some time to get back to work on this.


a pic found on the Internet of a functioning 1988-89 XJ40 Vacuum Fluorescent Display Instrument Pack

The vacuum fluorescent display (vfd) Instrument Pack (IP) in my 1988 XJ40 went south. The speedometer and tachometer work but the only thing that works on the display is a flashing orange rectangle in the VCM area.

Quite frankly, I was reluctant to drive the car much in this condition; only the speedometer and tachometer worked. I had NO idea if the alternator was charging the battery, how much gas I had left in the tank, if the engine was overheating, or how much oil pressure the engine had. Worse still, I had no odometer reading and thus, could not get the car inspected in this condition.

What to do?

After ensuring the behind dash electrical plugs had power where needed, I decided the IP was toast and went searching for a replacement. I found from a search on the Internet that these vfd clusters were troublesome and prone to failure. I found several on eBay, but they were expensive. Plus, there was no assurance that they, too, wouldn't die in a short period of time after putting it back into service. Mine had 118K on it and the ones I saw for sale had even more miles on them.

From my research, I found that the 1990+ MY XJ40 Instrument Packs were upgraded to analog gauges. If these go bad, it seems one could just swap out bad gauges for good ones out of another IP.

Perusing several wiring schematics, I found most of the requisite wiring was in my 1988 harness; it was just spread over 4 connectors which were quite different from the two used in the 1990+ MY packs.

I found little information on how to accomplish this task on the Internet. The most I found was that "someone posted somewhere that someone told him, that it was possible". WTF?

So, I subscribed to the old adage, "where there's a will, there's a way" and pushed ahead with the idea.

If the reader decides to go this route, I strongly advise him/her to shop for the required parts. The prices vary widely.

I bought a 1990 Instrument Pack (IP) from eBay for $40 + shipping. I found another locally for $10. I also found two more mal-functioning 1988-89 IPs for another $10 each.


found eBay pic of the back of a 1988-89 XJ40 VFD IP showing harness connectors

You are going to need a junk 1988-89 vfd IP in order to cut several of the connector plugs from it. There are four. You may want to use your faulty one ... or get another for a donor.



You are also going to need the two plugs that fit into the back of the 1990 IP. I found my 1990 plugs for $10. They came with lots of wire because I clipped them myself from a junk car. You will need at least the parts labeled 1 and 2 (and prob 2a) found in the above pic.

 

Yowza, anxious to see how this develops! Good job.

 

very interested in this!

 

Thanks ixfn.

You and rhoades please stay tuned. I hope not to disappoint you.


photo found on the Internet

This is a view of the back side of the 1990 IP showing the two unusual sockets where the 1990 wiring harness "plugs in".

In the various schematics I've read, the sockets and plugs are referred to by the following.

In the IP:

• socket A is 24-pin

• socket B is 48-pin

Wiring harness mating plugs:

• LB134, 24-way Grote (Black)

• LB135, 48-way Grote (Black)

 

Good job

 

Thanks, RegentV12.

In order to make the project more manageable, I decided to subdivide it into four milestones. I planned to make operational (in the following order):

1. the instrument gauges,
2. the odometer display,
3. the turn signal indicators, high beam indicator and other low-tech signals, and lastly,
4. the keypad, cruise control and remaining vcm circuits.

At least, that is my game plan.

Here are a couple of things I found out about the Instrument Packs.

• Follow Haynes and the IP is easy to take out. Only 4 machine screws hold it in place; two on either side along its lower left and right edges. Just make sure you pull/adjust your steering wheel all of the way back before attempting to remove the IP from the dashboard. It is a little tricky to pull the IP out completely so take your time and do not force it and do not scratch it.

• The 1990 IP fits perfectly into the 1988 dashboard. Enough said.

My first prototype harness adapter (pha#1) only partially lit the backlights. The dimmer did work. I may have issues with some burnt out lamps.

I rechecked the wiring diagram several times and finally came to the conclusion that I was missing a +12V feed line. The following photos are from using pha#1b.


initial test of pha#1b

This photo is taken with the 1990 IP in place (no screws), pha#1b hooked up, the battery connected (after the IP was connected to the harness) and the ignition key inserted but in the OFF position.

Notice the LCD is lit, albeit with some garbage characters. I was smiling when I saw this. It wasn't ON with pha#1.

Also note the 1988 keypad on the right in the picture.

 

Here is a picture of the IP just after I switched the ignition key to the RUN position.


IP display just after ignition switch was turned to RUN position, engine is not running

NOTE:

1. the ammeter gauge is showing discharge, as it should with the engine not running
2. I have just under a quarter tank of gas
3. I have an odometer reading in the LCD! This IP shows 145,151 miles.
4. only three of the seven lamps in the AMBER secondary warnings on the left are lit. I know the bottom one is missing.
5. all seven RED primary warnings (hazard/fault condition) on the right are lit and
6. the remaining eight lower lamps are a mixture of status and warning lamps and all are lit.

I was grinning from ear to ear after seeing all of this taking place!

 

Nice swap, be good when you get things fine tuned.

PS the status bar on my 92 is slightly different from your new 90, don't know if this would be a factor if someone got hold of the later replacement pack.

 

WOW, excellent job, better than odd lookin' digital gauges . Your Spor mode light is on the right side of the gauge , mine is left I didn't know that
What I like the most in digital gauges is you can see PRND32 wheras there is no room left for our rides , what a shame lol

 

Thanks gentlemen. I haven't hooked up a signal for the SPORT mode light and was glad
to see it went out w/o any further to do.

After a few seconds, I heard the µ-processor "kick on" and this happened.

I know you guys with these Instrument Packs are familiar with this behavior but this
was news to me.


key in RUN position, secs later when IP µ-processor "kicks on"

Most of the lamps turned off. Odometer reading stayed ON!

The warning indicators still ON are:

• automatic transmission failure,
• low windscreen washer reservoir level,
• circuit failure (I do have a blown fuse),
• ignition light & battery alternator fault

(understandable since the engine is off and I am draining the battery),

• the BRAKE system fault,
• low coolant level and
• low oil level pressure (engine is cold and not running)

Let's see what I happens when/after I start the engine ...

o

 

I started the engine and released the key from the START to the RUN position.

Allowing the engine to run for a few minutes, I took this picture.


Instrument Pack display with the engine running and warm

Notice:

1. the ammeter gauge is showing "charge" condition, the needle is on division 14
2. tachometer needle is on 1100 rpm
3. the lamps, ignition light & battery alternator fault and low oil level pressure fault, have gone "out"
4. oil pressure gauge is on the 7 mark and
5. coolant temperature is on "N"

It appears the engine is being monitored again.

o

 

With the ignition key off and removed, the LCD faintly shows the odometer reading

… that is, as long as you do not disconnect the battery.

o

 

The speedometer didn't work, because I simply hadn't hooked up the speedometer "cable".

The "cable", in this case, is a transducer type: two electrical wires covered by metal sheathing. This "cable" has to be spliced between the 1990 pigtail/plug which connects to the cluster and the 1988 male pigtail/plug which snaps into my car's harness.

I always disconnect the battery before fooling around with the cluster. After some reasoning, I spliced it, re-connected the harness and took the car out for a "gas run".

I found the speedometer now works in the 1990 MY cluster and so does the odometer as it it continued to update its display as I drove around.

No brag ... just fact.

o

 

My compliments on an excellent tech article ... pics too!

 

Hey Retro how is your project coming,(winters coming)

 

Thanks for the compliment, retromotors. I appreciate that. That's a nice avatar you have.

Moving on ...

So, I've accomplished my first two milestones, and when I return to this thread, I'll be working on item #3.

I'll try to remember to take a pick of my sub-harness, pha#1c, the next time I remove it.

PS I took the car to a local car cruise yesterday - even with sun burnt paint (clear coat fading and peeling). I received a very nice car plaque from the hosts. After all, the car is over twenty years old.

My motto is: If it runs ... drive it. Acceptable paint can come later.

o

 

Hi Trick,

If you are planning a trip to Oz bring a VFD with you for my '92 XJ6.
The VFD looks goods mate.We could swap them over?

 

If I ever do a "walk about" your way, I'll look you up.

Do you mean swapping a '92 IC (instrument cluster) for an '88 - '89 VFD IC?
I would venture to guess, yes, I think so. You may have several signals missing,
but for the most part, I think it would function.

However, you'll have to butcher your car's harness or find mating sockets
that match the ones soldered into the boards of the '92 IC in order to splice
into the 4 connectors of the VFD.

If you change your mind someday, you always want to easily put things
back to factory spec.

My only problem with the VFD is I could find no schematics in order to
troubleshoot it - aside looking for starved solder joints. There are many pc
boards to fool with. However, if I ever locate a functioning (and cheap)
VFD type, I can still easily plug it into my car's harness by just removing
this sub-harness.

Why? It may add to the vehicle's worth someday when that time comes to
sell her. From a reliability point of view, I would still run the car with the
90+ IC.

~~~~~ continuing

This is a pic of the sub-harness to date.


visual of pha#1c

o

 

I am very impressed you have achieved this.

My 1993MY 3.2 litre UK spec car has the same ZF 4HP 22 transmission as your 3.6 litre car. On my car the auto transmission light comes on for a second on switching on the ignition, then goes out. The same 4HP22 transmission was used on the 2.9 litre 1990MY cars (though not available in the USA) so there should be some provision for the light to extinguish as it should on your car.

The garbled message will appear on the mileometer every time you disconnect the battery before the ignition has switched on. After switching on the ignition, the mileometer displays 48560 for a second, then will return to the correct mileage. Just though I'd warn you!

David

 

David,

Thanks for the input and praise.

I'll be returning to this issue.