94 XJS 4.0 5-speed. Early model. 185K. After recent car wash, security fob no longer locks/unlocks doors or trunk. Manual lock/unlock driver's side door does not automatically lock/unlock passenger side. If trunk is locked manually, unlocking driver's side door will unlock trunk.

Fuses under dash, both sides, are good. No problem with manual lock/unlock except for trunk which I have trouble manually unlocking (assuming separate problem). Security system arms/disarms fine and alarms all work.

In addition, the passenger seat forward/backward adjustment switch no longer working. Recliner switch works.

I am a new Jaguar owner without a great deal of experience diagnosing electrical problems. My skills are limited to installing stereos and I have a good working knowledge of meters and test lights.

Any thoughts on these problems would be greatly appreciated.

 

Start with making sure the battery is fully charged. Go around the car and check that all the ground points are secure and clean.

Try that first before anything else.

 

I agree with Jim, make sure the battery is fully charged. Many of the car's systems seem to be very sensitive in that regard.

I have actually had this problem when the car has sat for several months. What happens is the lock mechanism gets stiff from either a lack of lubrication or use or both. Sit in the car with doors closed and make sure the locking tab is all the way forward. Then pull the tab back to the locked position. This should lock all the doors. If it does, do it a few times and see if that loosens things up.

The trunk lock has 3 key positions that control if the trunk is locked/unlocked by the central locking or not. I can't remember if you turn the key right or left and then back to center but check your handbook or just play with the positions.

Cheers,

Allan

 

Oops I missed the seat problem.

The seat controls can be a bit finicky There are separate fuses for fore/aft and recline have you checked the fore/aft fuse?

If that's ok, check the seat control module. There is one on the floor directly in front of each seat under the carpeted cover. If the car has ever been out in the rain with the top down, moisture can get trapped down there and cause all kinds of funny things to happen. disconnect the plugs and clean the pins, check earths etc. If no change then you will have to check the operation of the door panel switch.

If you haven't already downloaded the electrical guide, here it is. Trust me, it will be your friend It's quite straightforward and easy to use. http://www.captainjaguarscathouse.co...ec%20Guide.pdf

Cheers,

Allan

 

Jim, I'm a novice at the electrical stuff. Where would I find the "ground points?" I've looked at the electrical diagram. What would they look like?

 

Ok, have a look at the negative terminal on the battery. The lead that comes off that is then bolted to the car. That is the thing you are looking for.

There will be a few in the engine bay. What you need to do is unbolt it from the car body, clean it, lightly grease it and then refit it. Also make sure the point it touches the car body is also clean.

To find them all you will need a manual or if you are lucky someone may copy the page and post it for you.

Also check the battery in the fob and clean if needed.

Agree with Allen on the lubrication of the door locks.

Hope this gets you started.

 

In the electrical guide referenced above you will see that for each wiring diagram there are two pages. One is the wiring diagram itself and the other is the data page. Simply find the ground point you want on the diagram and then look at the data page for its location.

Cheers,

Allan

 

I'm not getting a lot of time to work on this so progress is slow.

I did look at some of the grounds last Sunday. My meter is not digital but the battery appears fully charged with 12+ volts. Battery grounds in trunk are solid, clean connections with no corrosion. The other grounds I've looked at in the engine compartment are in the same condition. I am cautious about undoing and cleaning connections that show no sign of wear but I will if you guys still think it prudent. More grounds still to check.

In a couple of places, the ground connections are listed as located at the "left 'A' post" or "right 'A' post". The "A" post is located on the right side at the back of the engine compartment but there are no ground points to the right or left. There is what appears to be a ground point in the firewall to the left of the "A" post with several ground connections (I assume). Is this the location I am looking for?

There is also another ground point listed as located under the "trim cover". I know how stupid I sound but where is the "trim cover"?

Some other clues I did not mention:

Temp gauge is all the way over to the right most of the time but once in a while will start working again and show the temp as at or below normal. There are no secondary indications and the car is running great so I know its not overheating.

Battery gauge ticks down slightly from 14 volts whenever I hit the brakes. Again, battery is relatively new and holding a good charge so there appears to be no problem with the generator.

Oil pressure gauge pretty consistent at 15 psi but every now and then will tick down to about 8. Oil level is fine and no leaks so I'm assuming pressure remains good.

Recently, the gas gauge has been acting up after I fill the tank. For the first few miles, level will fluctuate between full and nearly empty with the warning light flashing on and off. This settles out after a while and the gauge begins working correctly again. I am not leaking any fuel and my mileage is consistently above 19 mpg.

The other day, I turned on my stereo and heard bad static from the speakers. Turned it off and on and static went away.

All of these problems seem consistent with an intermittent short in ground connections but if anyone has any other suggestions, thanks in advance.

Jim, I should grease the connections after cleaning--like with WD-40? Will this not interfere with the connection?

 

Hi Again,
With your last comments on static and intermittent gauge operation,
it points to a ground problem, you just haven't found it yet.

A manual will show exactly where all ground points are for your car.

As for greasing ground points, once clean and refitted simply lightly smear some petroleum jelly or Vaseline over the terminal, nut and stud. This will keep corrosion at bay and aid in the conductivity of the ground point.

Keep up the good work, you'll get there.

 

I agree with Jim's comments and I would add that often the earth connections can look 'clean' but are not. I would definitely recommend undoing the nuts and then cleaning the mating surfaces with a wire brush to remove any oxidation. A bright, shiny finish is what you are after. Don't ask me how I know this

In most cases when the manual talks about the 'A' post, it is referring to inside the car not the engine bay.

The 'A' post has hard vinyl trim covers at the bottom in the driver's and passengers footwell (remove them and the carpeted panel behind) There is also a trim cover than runs up and down the inside from the roof to the dash on both sides.

Yes, very much so. For the gauges, you will need to pop open the instrument panel and check the connections at the rear. This is a VERY common problem with our cars

Keep it up, you are making progress with every connection

Cheers,

Allan

 

Ok, fellas, I managed to get something done. While looking for the control lock module, I found and fixed the passenger seat problem. Apparently, someone wanted the cigar lighter to work without the key in the ignition. They clipped the lighter fuse and spliced into the passenger seat power at the fuse block. The splice was badly done, though, and the solder on the battery line broke killing both devices. Repaired now. Anybody have any idea why someone would do this? I'll be back to looking at grounds, tomorrow.

Ok, this tells you how stupid I am. After a bit of searching, I now understand the A, B, and C pillars, or posts, refers to the cockpit area window supports--not some kind of mount or fixture bolted to the car. Thanks for your patience.

Allan, thanks soooooo much for the link to the electrical guide. Big, big help. Couple of questions about ground locations:

Gound location for the fuel level transmitter is listed as "RIGHT REAR INNER WHEEL ARCH / POWER GROUND." Is this one of the ground points right of the battery in the trunk or should I be looking under the car?

Ground location for the Door Lock Control Unit is listed as "LEFT TRANSMISSION TUNNEL ADJACENT TO DASH SUPPORT / LOGIC GROUND." Do I need to remove the center console to get to this ground or, again, should I be looking under the car?

Thanks again for all your help.

 

I believe that is correct, as I recall there are at least three ground points located there. The "RIGHT REAR INNER WHEEL ARCH" can also mean behind the trim piece to the right of the battery cover too, so check there as well. This is where you will find the fuel pump relay which may come in handy at some point


Yes, it is under the console.

Glad to see you are making progress

Cheers,

Allan

 

How much effort is this, Allan? If I start today, can I get the car back together by tomorrow?

 

It's pretty easy really, the procedure is described in the service manual if you have one.

If not, first disconnect the battery earth terminal. Then remove the 3 screws that you see inside the instrument panel hood.

Then pry off the two small cover plates in the top corners of the instrument panel and remove the screws behind them.

You can then ease the panel forward and disconnect the plugs in back. The panel can now be removed.

That part will take 5 mins tops. Now you can inspect the connectors and make sure everything looks clean and tidy. If you have any bulbs out on your instrument panel, now is the time to replace them..

If you need to replace any of the gauges themselves, you have to take out the bulbs then undo the nuts that hold the printed circuit board to the assembly and remove it. (Just be careful not to damage any of the tracks or components on the board)

Depending on what you find, it could be a quick 30 min job or might take as much as a couple of hours of you need to replace any parts. It's quite easy though.

Cheers,

Allan

 

If the windows stopped working right after the car was washed, then chances are water got in the switch and fried the window switch out. http://www.switchdoctor.net 30 day return policy, Lifetime Warranty.

 

Ok, got the door locks working again. Here's how I went about it in case it helps anyone else.

Since I'm such a novice, it took me a while to locate the module. Thought the wiper module was it, at first, till I ran the model number. Finally found it inside the right A post. At first I figured the module was probably bad--disappointing considering the cheapest replacement I found was $110.00 for a used one--so I removed it and started to set up a jig to test the signals. I was a bit nervous since the only 12V DC converter I had kept registering 14V on my meter and I was concerned about overloading the circuitry.

Before I got started, I decided to check the signals coming in to the module. Battery power, hot; switched power, hot; lock input, ground; unlock input, ground.

Wait, what?

It seemed pretty clear from the diagram that only one of those inputs should be grounded at a time. I then remembered that a couple of times, when testing the alarm, the locks would lock and then unlock--again and again. I also remembered the lock did not actuate on the passenger door. I suspected the unlock ground signal was coming from that door so I removed the panel, disconnected the plug, and voila! The locks started working again.

Turned out the problem was not electrical, at all, but mechanical. I'm not quite sure exactly how the mechanism was supposed to work because I could find no pictures of the locking mechanism on the Internet and didn't want to take apart the other door. But when I looked at the plate connected to the rod connected to the plug module, I noticed it looked like it was once connected to a plate on the locking mechanism with a missing cotter pin and was now hanging down below the other plate. Suspecting this as the cause of the constant unlock ground signal, I jury rigged the plates together with a precision screwdriver and again, viola! No more unlock ground signal and the locks all worked perfectly. Having no cotter pins handy, I used some heavy steel wire as a makeshift to repair the mechanism.

Funny, isn't it? Washing the car had nothing to do with it. I think this happened because my wife and my son are always slamming the passenger door no matter how much I bitch at them. Boy, are they gonna hear about this

Thanks for the howto on the dash, Allan. I'll let you know what I find.

 

Glad you got it fixed! I'm not surprised that it was something mechanical, although I've not seen the cotter pin issue before.

All's well that ends well eh?

Cheers,

Allan

 

Those of us with an electrical bias can only hypothesise given the symptoms without seeing the car.

Those with a mechanical bias will generally blame everything on the electrics.

So glad you took the time to have a look and find the problem and fix it. More importantly, keeping the forum in the loop with the result.

Cracking job, keep it up.

 

I'm down to the last problem on this thread, fellas. The convertible top just needed more hydraulic fluid. I was worried about a leak but checked the whole system and couldn't find one. Just have to keep watching it.

Allan, I have not opened up the dash, yet. I decided to check the resistance at the temperature sender. You'll remember one of the problems I had was the temp gauge needle going full to the right immediately after startup. Now, the temp sender is in the thermostat housing with black and blue wires (electrical guide says black/yellow and blue/yellow but I'm pretty comfortable I've got the right sensor). Seems reasonable to me that if I disconnect the connector, the gauge should go cold all the time. However, the needle stays pegged to the right. If I disconnect the orange wire on the sensor next to the temp sensor, the gauge goes cold. I can't find anything in the electrical guide about this other sensor with the orange wire. Can you shed some light?

I only have a 1K ohm meter but when I check the leads on the temp sender, it registers < 1 ohm after the car has been off for over 30 minutes. I don't know what the engine temp is, right now, but I'm assuming no more then 100 F and I should be registering 1K ohms resistance at that temperature and more as the engine cools.

Is there any reason I should not think the temperature sender is bad?

 

There are two sensors on the thermostat housing the two wire connector is for the coolant temp sensor but this only feeds the ECM for fueling strategy.

The other single wire connector is for the coolant temp transmitter, it directly feeds the temp gauge on the dash. Sounds like it is working as the gauge went to cold when you disconnected it.

If you disconnected the temp sensor when the ignition was on you have a check engine light on. I can't remember the DTC code but that sensor will throw one when disconnected.

You could maybe measure the output range of the transmitter but my money is on the gauge end of things.

Cheers,

Allan