Hi, I am new to this forum. Allow me to introduce myself, my name is Robert and I recently bought a 1988 XJ40 Sovereign. I have always loved Jaguars and this is my first. I got it for a song, knowing there would be problems, but it seems as fast as I solve one problem I get another one to replace it.

It seems it has a few faults that I have been slowly remedying. The first issue I addressed the fuses to make sure they were all present and functioning. Almost all of them had a thin brown/grey coating over the terminals, so I Painstakingly sanded each one and then tested them with a multimeter and replaced those that were blown.... all good now. (will replace them with new later)

Next I addressed the problem with lights, firstly the interiors.... map reading and overhead console... all working
I then went to work on the headlights, the high beam worked fine but had no low beam..... replaced the globes and they too now work.

Problem inquiring about:
Today I went out to the car and tried starting it to find that it had an almost flat battery, I then realized that the instrument panel was lit up, all the gauges, odometer and diagnostics were actively displaying even though the ignition is off and the key is removed.
After a little research online, I tend to think it may be the illumination module... but I am not sure and would appreciate any advice from anyone who may have had this problem, or an idea of what the problem may be.

Other Problems:
I am also getting low brake pad low warning (have ordered new pads), low brake pressure warning (hoping this may be fixed with the new pads and possibly bleeding) The booster sender unit seems fairly new, also getting circuit 1 and 2 warning (I have no idea what they are yet...), and coolant level low warning and Brake fluid low warning even though it is full (I think I need to replace the sender unit for these two).
I have ordered a workshop manual, hopefully that will tell me the error message meanings (circuit 1 &2).

The blower fan for the heater & A/C also does not work, I believe I can hear the compressor cutting in and the motor changes pitch and I can feel a slight cold from the side vents, but nothing from the centre vent at all.

I would appreciate any advice
thanks in advance
Robert

 

Robert

Welcome to the forum. In regard to the LLM (Light Logic Module) you may have poor solder points on the board. I removed mine and found cold solder points. Pay particular attention to where connector leads or any leads for that matter, terminate on the circuit board. My issues was related to the "Lights On" audible sounder would sound, even with the lights off and key removed.

Not sure if you have the digital dash or analog, but if digital the instrument cluster itself may have many cold solder joints. This too may be the culprit.

In regard to the various warning indicators for the brake system. Do you know if the brake system has been converted to a traditional booster system? If you're not sure, take a pic of the engine bay area for the existing system and post it to this thread, we will be able to tell if converted or not. A poorly done conversion, may leave some connectors for the original system "untidy", thus producing warnings that are applicable to the prior brake system. If we can eliminate that no conversion was done, we'll move on to helping you troubleshoot the original Jaguar system.

There are two blowers for the XJ40, they work in conjunction as opposing forces, and if one is not working, the other simply blows through to the other side and the efficiency is greatly diminished, thus little to no center vent flow. With a fully charged battery, key to on position, turn on the fans and feel each fan assembly to see which is working. Additionally, locate the respective fuse and pull them one at a time to identify the bad blower.

If you do identify an non-functioning blower, it will need to be pulled and worked on. Could be badly worn brushes or other components such as a relay or resistor. There are plenty of threads that explain in detail how to repair.

I'll send you a PM with a document that fully explains the A/C system.

 

Hi Rob Evenson,
Thanks for the welcome.
As I said I am new to Jags, so please forgive my ignorance.
When you say the LLM, is that actually a separate module under the dash somewhere, or is it the circuit board in the casing at the side of the steering wheel where the light switch actually is. Yes mine is still the original digital dash.

As for the brake system, I believe this has the boosted upgrade. There is a booster unit in the front corner under the bonnet (Hood) behind the headlight, I believe it is the proper jaguar conversion, but I could be wrong. (new brake pads arrived this morning)

As for the blowers, I have in fact looked at a couple of other posts on this forum regarding this, and they have some very detailed information and step by step photos, so I think I may have that one covered for now......

My main concern at this time is getting the instrument panel to switch off and prevent the battery constantly going flat. I am finding it impossible to drive the car as it will not hold a charge long enough.

thx

 

Robert,

The LLM is the same circuit board you are referring to where the off/park/on switch is located.

The digital dash can have many gremlins itself, mainly bad solder joints. If it starts behaving badly, as in the gauges flashing brightly or going out temporarily, you'll need to pull it and check the joints.

My suggestion for checking the blowers is based on experience of having to pull them out. You want to be sure, very sure, you're pulling the correct one. They're a bear to get out and then the joy of reinstalling.

Keep us posted, good luck.

 

Thanks again Rob.....
I will have to look into it and get the old multimeter out and check some circuits on the board.
Also thank you for the very detailed info on the blower system, that will be a great help to me once I get to that problem... I do appreciate it.

Seems I have a new problem.... like I said the dash lights are staying on constantly, thus I ended up with a flat battery. I charged the battery overnight and connected it again 20 minutes ago and the car started first turn of the key, however when returning the key to the off position..... the engine did not stop, just kept running.
I ended up pulling the HT lead from the distributor to make it stop and got a nice little boot in the process

any idea on this one?

 

I believe I can rule out the light switch itself as the problem.
I have totally removed and unplugged the light switch board from the steering column and then reconnected the negative battery terminal....
the dash lights are still on...

this combined with the new find that the car will no longer turn off once started leads me to believe that there is a short or something on the ignition that tells the car the key is in the on position when it actually isn't.

Is there some relay or something for the ignition that may be a bit dodgy??

hope someone knows something about this and can guide me to fixing it

 

Robert,

I have not had any such problems, however just yesterday, on another jag forum a guy reported similar symptoms such as yours. What he ended up doing was disconnecting the battery and thoroughly dousing the ignition barrel. He speculates that one or more of the barrel keys were hanging up and not resetting properly. Never know, sometimes the simple stuff works.

That said, I would also pull the ignition relay and clean it along with the relay base. The circuit starts with key to start position, which energizes the ignition relay and starter relay, then onto the starter solenoid. Be aware, the ignition relay transfers signal to the starter relay via the linear gear switch, then onto the starter relay to complete the start circuit to the starter.

Another thing, this vehicle is sensitive to dirty earth ground connections. Clean everything you can find. There are two, one on each side of the engine bay, directly behind the headlights. One directly behind the cam cover on the firewall. The battery negative ground is located ..... you can find that one I'm sure. That is not a comprehensive list by any measure, perhaps someone has a location list of all. Bottom line, where ever, when ever you see a ground, clean it.

There are two in the boot, one each side, behind the finisher carpet boards, directly below the BFM's (Bulb Fair Module). Those I've described that I can think of are particularly exposed to more grime than those located in the cabin. Many have reported gremlins suddenly disappearing with a good housecleaning.

I sent you an email with the starter circuit diagram.

 

update:
after sitting here pondering what changes I had made to the car while trying to isolate problems, I remembered I placed a relay in a slot in the boot that was missing from the left quarter panel (grey relay ... cover says "Over Volts") I decided to remove it just to eliminate this as a cause as it was the only change I made prior....

This fixed both the dash illumination problem and the not turning off problem.

So what is the "Over Volts" relay for and is it necessary for the vehicle?

 

thanks again Rob.... you truly are a champion.
I appreciate you taking the time and effort to help me out.
Eventually I will learn all the ins and outs of this car... it will just take a little time.
I have been fixing and restoring cars (and bikes) for many years but working on a Jag is a first lol