Brand new to the Forum. Busy fixing up a 1991 XJ40 Daimler.
Just had a quick question if anyone has come across this before - so this vehicle has had some bad water leaks over the years, and I’m stripping everything out and fixing one by one.
I have kinda managed to get the car to start and idle… sometimes, but i suddenly had my instrument cluster go out completely - i have a spare - and that’s dead if i plug it in too, but looks like the CPU (Not ECM) has had some water go through it over the years - if this module has blown, could that cause the cluster to have gone out?
I have opened the CPU and its in pretty rough state, but cant find anything online that says whether the cluster is controlled from this module. I have no lights and no instruments that come on.
I have double and triple checked all fuses - they are definitely all fine.
The instrument cluster should receive ignition-switched 12 volt power on pin 2 (orange/white wire) in a 24-pin black connector in the back of the cluster. The source is fuse #6 (5 amp) in the center console fuse panel.
Here is a link to the 1990 Jaguar Electrical Guide if you would like to download it:
You are a legend. I’ll give this another look. I did have a very close look at Fuse 6 already, but perhaps ill check that pin 2 to see if anything is coming through.
Well, thanks but no, no legend, just a Jag lover. Now Ed “Big Daddy” Roth, the creator of Rat Fink, there’s a legend. Let us know how you get on with this opportunity (with Jags there are no problems, just lots of opportunities!).
Oh i’m going to have lots of opportunities before this one is going again. Thanks for the help though - at least now i know i am getting 12v to the cluster, and managed to get at least the backlights going.
Still not a single instrument functioning though, not even getting rpm when cranking/starting, so it would seem its not getting “data” wherever that’s coming from.
Not so weird in that the instrument cluster is receiving inputs from the monitored system/component, mostly signal level (5 volt).
You have verified that you have 12 volt power to the panel on pin 2 (orange/white wire) in that 24-pin black connector so perhaps the next check should be for ground. Referring to the Inputs/Outputs data in the Electrical Guide:
pins 3 and 4 (black/pink wires per the wiring diagram) in that same connector provide logic (signal) ground, so check to see if you have continuity to ground with each of those pins.
Sorry for the delay. I finally got around to testing the continuity. My multi-meter is pretty basic, but from what I am seeing i believe i do have continuity to ground on both pin 3 and 4.
So with the 24-pin connector unplugged from the cluster, one probe touching pin 3 (or 4), and the other probe touching a known good ground point, you are getting the tone (if your meter has a continuity setting) or seeing a reading of zero (if you are using a resistance [ohms] setting)?
Depending on the range selected on your meter (if it is not an auto-ranging meter) that 1.4 ohm may be as good as a zero reading. If there is any doubt you could temporarily rig wires directly from pins 3 and 4 in the connector directly to a ground.
The next step may be to check an input to the cluster, although it seems very unlikely that ALL the various inputs would be bad/missing. An easy one to test would be the high beam indicator, pin 24 in the 48-pin connector. Per the previously posted table, with ignition and headlights on, that pin should receive 5 volts unless high beams are selected when the signal should go to ground.
I really should buy a better multimeter, but yes that was my suspicion, as probing a bolt gave me 0.9 ohm so figured that is pretty much a zero rating.
Your thoughts are spot on - i also could not understand why i was not getting a reaction for a single instrument component.
I can test your suggestion - just wanted to confirm that none of this is running through any kind of control circuitry like the CPU (or comfort control module) (DBC4966)
