Fitting a Trip Computer to a 3.6 Manual that didn't have one from the factory..

[SimonR]

Hello chaps,

I remember reading somewhere that it's possible to remove the analogue clock its veneered trim panel from a 3.6 XJ-S and just plug a trip computer straight in as the wiring is there already to make it work.

It's something that I want to add to my car for the ultimate in '80s electronics (it's not as pretty as the clock, but I quite like the extra functionality, too) so if it's as simple as plug and play, I'll get hold of a couple of replacement bits of trim for either end and do it.

The computer units (P/N DAC 4452) appear to be readily available and inexpensive.

Many thanks

[davidr]

Hi Simon - I think it is "plug and play" but maybe it's worth checking you have the connectors before you make the investment?

[poprivet]

You will also need the wood panel.
The connector behind the clock is the same, the computer just has more wires connected.

I tried a similar conversion some years ago but I couldn't get the fuel to read out. Possibly I was sold a faulty unit but the V12's had a fuel interface which my late 3.6 doesn't have.

Not sure if the computer is the same for the early and late 3.6 models as the fuelling system is completely different.
Ultimately I decided the analogue clock was nicer to look and also I didn't want to be reminded of the fuel consumption.

[SimonR]

Thanks for the replies gents - I took the clock out and found exactly what you describe Pop - the blue multipug with loads of wires, but only the 12v supply wired into the clock.

I've taken the plunge and ordered a NOS DAC4452, which has the same blue multiplug that my late 3.6 car has:

https://www.ebay.co.uk/itm/165283324176 ... Swj69h4Y2T

It looks like the earlier cars had a pair of bullet-type multiplugs on a part number of DAC4295, like this one:

https://www.ebay.co.uk/itm/334243500592 ... Sw6ZVhrLEy

I've got a pair of the wood surrounds in my stock of XJ-S spares, albeit the wood veneer is in poor condition. I'm tempted to re-veneer them myself as it's hopefully not too difficult a job. I noticed you can get the right-looking shade of Elm also on eBay e.g.

https://www.ebay.co.uk/itm/134016968199 ... SwlpdiADGW

They're selling consecutive veneers so there's the possibility of book-matching the panels to make a nice job of it.

I'll report back how I get on

[SimonR]

I did the swap today - luckily I'd forgotten that I had removed a good condition set of veneered switch panels from a car with a trip computer that I found in a scrap yard a few years ago. I spent a very happy hour or so sorting through my stash of spare parts - the other thing I found which may be handy in the future is a set of stalks with the speed control button on the left hand one. The first part of the jigsaw for fitting cruise control some time in the future.

The NOS computer arrived yesterday so I had all the parts i needed:


Half way there


Job done.

It was a fiddly job as getting the original panel required quite a bit of gentle aggling and prying with a trim removal tool, and then the trip computer was a really tight fit.

I got there in the end.

[poprivet]

That looks great, just need to change the air outlet for the later version now!

Lets the air frow to where you want it, not into the back.

[SimonR]

I'll look out for that later version Pop - I've always thought that the central vent was a bit lacking in direction. Mind you I've also yet to have an XJ-S with a working flap to allow air out of that vent so maybe this car will be the one.

I'm please to report that the fuel reading appears to be working on the newly-installed trip computer so that hopefully means it is fully functioning.

The car is booked in on Thursday to have the rear brake calipers, pads and flexi-hose replaced prior to MoT so with any luck by the end of the week I can test it out properly!

[SimonR]

I got a surprise today! Who knew that the trip computer also reports faults and faut codes? Well - OK, I'm sure it's common knowledge, but I had no idea.

I took the S out today for its first family outing and it was faultless, except for one little hesitation. The car was up to temperature and I'd just driven it in a reasonably spirited way along a favourite stretch of road, but when turning left at a T-Junction shortly after, it kangarooed a couple of times before returning to normal. My other half noticed that the trip computer was displaying 'Fuel Fail' and then when I turned the ignition off, it changed to #FF6.

Having looked this up it apparently means there was a discrepancy between the throttle potentiometer resistance and the amount of air measured by the air flow meter, so I'll have to get the multimeter out and see what's what. My hunch is that the previous owner very rarely drove the car in a spirited way so it could be that the throttle pot has seen very little action above a certain position, corresponding to whatever 70 is in 5th gear.

Anyway - in my mind, this added functionality (as well as the standard trip computer functionality) is reason enough to retro-fit the unit in the first place.