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First post in this thread below: Spent MANY full days on this – so now I am surrendering and passing over to the great guys on this forum, who have never let me down!
Came back from 3 weeks vacation and turned the car on – no dash lights, no system check, no messages, no gauges and car stuck in park. However! The car starts and drives fine (when taken out of park). Still none of the above – no speedo and no tacho, no oil pressure and no volts. After some time, we found that disconnecting the battery, turning ignition on THEN reconnecting the battery solved all the issues UNTIL the engine was turned off and the key removed. Then back to nothing.
Battery voltage without engine running between 12.1v – 12.4v. With engine running (but no lights or gauges) about 14.1v.
After continuously going through these cycles maybe 10-15 times we discovered that if, when you turn the engine off but only as far as the accessory position, everything would work. At times, we could even remove the key and it would still be fine. If the car is left for more than an hour or two, we were back to square one.
We also discovered that sometimes (not always by any means) we would turn the ignition on and after 15 seconds or so, the lights and gauges would come on.
I know some of you are already thinking, ‘It’s the battery!’, but the battery was new 3 months ago.
For complete info, the alternator failed a few months ago and was replaced with a used unit, which has worked fine.
Spent the Winter looking at systems periodically. Tried a new battery - no difference. Checked Instrument cluster wiring and fuses - no difference - replaced the ignition switch (lower part) - no difference.
A couple of times (in a 100) the tachometer will stay at 1000 rpm when the key is out.
Car still drives fine and lights and instruments come back after a few miles driving - but problem returns after being left for a few hours (Once driven a few miles stopped and re-started - fine)
ANY suggestions I am open to - this has me completely foxed - and can't find anything similar from searching the XK8 forums
Charge the battery for 6 hours at 2 to 5 amps and check the voltage across the terminals with a voltmeter. If the battery shows less than 12.6 volts, the battery is suspect and should be replaced.
Regardless of the age of the battery, it should hold a charge of at least 12.6 volts for all the system to function correctly.
Just a shot in the dark, but many times unexplainable issues are caused by a flakey ground. There are quite a few of them on these cars - grounding points.
Tried a new battery ( 950 MAXX Premium) - still only 12.3v standing voltage. No effect on problem. Remember also that if the ignition is left on and the battery is disconnected - then reconnected - the system lights up instantly the negative lead touches the terminal post. This happens every time battery is dis/reconnected.
Have cleaned the DPP junction box and replaced the battery leads with copper core cables to reduce any possible loss.
AAMOI, I checked the standing voltage on our other 3 cars - all were between 12.1v and 12.3v. Are batteries supposed to have a normal standing voltage of 12.6ish?
There are some slight variations on the battery voltage table depending where you look.
The main point is that jaguar cars like fully charged batterys.
I would say start by tracing the battery power to all the fuse boxes. Start in the trunk, and double check all connections. The trunk power block comes up as a problem once in a while. Battery cables themselves sometimes fail (hint: they get hot). Then move to the engine compartment and double check all the supply cables. Same with the "facia" boxes when you open the door.
If this does not lead to anything interesting, it is likely time to download the electrical manual, start at the known problem area, and work your way up. Your description makes it sound like some relay is possibly sticking. The early pages in the manual describe high level power distribution. They seem abstract and hard to read but worth doubling down and figured out. A known technique is to swap the same relays around to see if anything changes.
Last, you should probably check if any OBD codes are available. It would tell you at least if the ISO bus is working, and there likely would be a code if CAN was not operational (speedometer input). If the IC is powered off, it is likely an important problem as it houses the bridge between data bus technologies.
Tried a new battery ( 950 MAXX Premium) - still only 12.3v standing voltage. No effect on problem. Remember also that if the ignition is left on and the battery is disconnected - then reconnected - the system lights up instantly the negative lead touches the terminal post. This happens every time battery is dis/reconnected.
Have cleaned the DPP junction box and replaced the battery leads with copper core cables to reduce any possible loss.
AAMOI, I checked the standing voltage on our other 3 cars - all were between 12.1v and 12.3v. Are batteries supposed to have a normal standing voltage of 12.6ish?
Yes a fully charged battery will be 12.6-12.8V so possibly your meter is faulty but did you put the New battery on charge for at least 12 hours? They commonly claim they are fully charged but they're not.
Here's the ground connections from my electrical manual (Gen1), plus I've attached a great document from Gus' www. jagrepair.com site. I went through this initially when I initially got my car and it seemed to fix all sorts of funny warning messages I had. 12V isn't a lot to start with so any voltage drops due to bad grounds tend to lead to all sorts of funny messages in our car.
The main troublesome culprit for me was the engine block ground. Pic below.
Thank you all for your replies - especially David for his detailed pictures, PDF and links. I charged my new(ish) battery for 24 hours and immediately tested the output - 12.55 volts (with 2 different voltmeters).
Connected up - ignition on - nothing. left ignition on and disconnected negative battery lead - reconnected and all on/working. Started car and left running for a while. Stopped and left for a couple of hours - came back - nothing.
I did hear a while ago that there was a recall on the instrument cluster because of a soldering fault on the circuit board. Removed mine and checked under a magnifying glass - no sign of any problem. I am thinking I might replace the cluster as they are not that expensive but want to know that the car is not 'immobilised' if you do this. Understand you might have to have the new cluster flashed at a dealer - but no good if the car can't be driven there. Anyone no the situation regarding this?
I checked and cleaned all the major ground points - though not the one shown in David's pic. Will look at that tomorrow - but cleaning all the others had no effect.
that sounds like a fault on the ignition switch circuit. You connected the battery, nothing, left the ignition on and reconnected it, it works.....interesting.
Did you try connecting the battery again with the switch on?
Your battery voltage sounds really low - normally they're sitting higher than that.
I would start tracing voltages around the ignition switch circuit - could be a stuck relay on that circuit and the hot connection of the battery with the switch on could be giving it an extra kick....
that sounds like a fault on the ignition switch circuit. You connected the battery, nothing, left the ignition on and reconnected it, it works.....interesting.
Did you try connecting the battery again with the switch on?
Your battery voltage sounds really low - normally they're sitting higher than that.
I would start tracing voltages around the ignition switch circuit - could be a stuck relay on that circuit and the hot connection of the battery with the switch on could be giving it an extra kick....
good luck.
i suggested that and got a sarcastic reply. Oh well.
Hi Brinny
Before I update on the issue I want to assure you I would never be sarcastic on this forum - I'm looking for help. I'm really sorry if it came across that way. I thought you were querying why I had replaced the ignition switch, as stated in my previous post. It was never sarcastic or flippant.
So, today I bit the bullet and went out and bought a new Premium AGL battery ($220) which registered 12.8v standing. Connected up and turned on ignition - nothing for 5 seconds then normal lights come on. Great! I thought!
Turned the ignition off but all lights and gauges stay on! Turned ignition back on and now EVERY warning light is on - indicators, airbag warning, ABS, Brake Warning, Yellow and Red warning lights - oil pressure at 0 and red light on, voltage indicator showing large discharge. Turned ignition off again but all lights and warning stay on! disconnected battery and waited a few minutes to allow any residual voltage in ECM to dissipate. Connected back up but lights still on (with key out) and oil warning and voltage showing large negative discharge?
I have to say I am losing it a bit and getting close to scrapping the vehicle for parts - it is a great car when it's running - but it has not run properly for a long time now - despite large amounts of time and money being spent - the enjoyment is waning fast
Couple of quick addendums. (1) All above but ALSO, with battery disconnected - voltmeter still shows 11v and fuel gauge stays at 3/4 full??
(2) When engine started - all lights as described above but message center stays at SYSTEM CHECK.
Have you checked the relays? Seems to me you’ve got a dodgy relay or ignition switch.
do you have a wiring diagram to work from? Start with the power distribution circuit to the ignition switch and check those components.
did you also try connecting the battery with the ignition switched on as you did before? And mentioned that the car started this way. Is that repeatable?
hence why we keep saying ignition switch or that circuit.
Crazy Electrical Faults!
