Anyone out there have any experience replacing these units? I now have 4 of them and they all (don't) work the same, although one of them wouldn't hold the time if turned off. Is there any other part of the system that could be causing it to not work properly? The latest one was from a low milage xjs. The fuel NO the avg speed NO instant speed NO. Do I have to wait for the computer to reset or something. I'm at my wits end. I'm hesitant to buy another one even if I'm promised it will work fine. any help will be greatly appreciated. Bud

 

The T/C doesn't have many inputs to go wrong.

It takes a signal from the speedometer circuit via the 'speed interface unit'.

Fuel injector pulses are translated into some sort of understandable language by the 'fuel interface unit'.

I'm not aware of any way to test either of these units....but someone might come along who does.

Of course the T/C also needs a 12v constant feed, a 12v key-on feed, and a good ground.

I'd begin by checking all associated connections. Do you have a good diagram?

Cheers
DD

 

I believe that the trip computer was programmed to generate completely random numbers in an effort to confuse us all; I use it to select my lottery numbers (it's crap at that too).

 

I installed one in place of my clock on my 95 coupe. It works well, the only problem I had was both bulbs for the display were bad and I replaced them with green LEDs. On the 95 it is a plug and play install as far as wiring is concerned. I did that at the same time I installed the factory front fog lights. Again it was plug and play. You do need the computer wood panel to replace the clock panel. 95 model year they removed the computer on the 4.0 cars.

 

Have you tested your four trip computers? I find it unusual that you managed to find 4, and all of them do not work.

I fitted one into my 96 and its seems to work rather well. Based on math and the odometer, it seems to match up with 1% of each other.

 

No I haven't tested them other than plugging them in to the dash. Other than that,I don't know how to test them. Do you? Knowing of an alternative way to test them would help me a lot. Thanks for any info. Bud

 

If they ALL have the same fault (you did not say what that was) then you need to start looking at the circuit that is not working. For example if the fuel consumption does not work but the distance does then the problem would be with the Fuel interface unit not the trip computer.

If you can give me more information on the exact issue I will have a look and see if we can sort this out.

 

my trip computer works quite well. fuel consumption is always within .1 of what the pump takes to top off.

i did momentarily have some trip computer issues when trying to track down another issue i randomly swapped some relays around under the hood. and my other issue went away but the trip computer started doing some funky stuff. so some more swapping of relays to isolate some bad ones and replaced a few and the trip computer is back to working properly.

 

You have four. If you know of another Xjs in the area, you can ask them to plug it in for you.

I live in DC. If you want to send me one, I wouldn't mind plugging yours in for a day or two to see what happens.

I'm thinking there should be someone on this forum that lives closer to you in NJ?

 

here's what I know at least about the last 2 I plugged in The instant speed stayed at zero but on occasion displayed 99 and then back to zero. the fuel displayed 0.0, and would slowly climb up to 0.3. The clock worked fine and I'm supposing, when I only pressed the minute button and the display would go off, that, was correct. If I pressed it again the display would return. The reset also worked. Thanks for the ongoing concern.Bud

 

Good idea! I'll look to see if there's anyone in my area to swap with .It should be a quick tell all. Bud

 

This is interesting. I have just started driving a 89 that I bought, and last Sunday the computer worked great. This Sunday, when I went for a drive, the numbers were all messed up, made no real numbers. After a while, the time came up, but it couldn't be switched to anything else, reset, or anything. I was searching tonight for another one, but sounds like there may be more to it?

 

Sometimes just unplugging and then re-seating the connector restores normal operation. You might get lucky !

OTOH I also suspect we'll be seeing more and more of the older trip computers going on the fritz. As novelty/gizmo gadgets go, it's a bit surprising (well, to me, at least) that so many have lasted as long as they have.

Cheers
DD

 

There is a speed interface unit, if the speedo is working correctly then the first thing to look at is the connector and loom from the back of the Computer. Check the pins in the connector for damage or corrosion.

If you can not find any issues with the loom or connector and want to post me one of the bad Trip Computers I will have a look at it.