I need a favor on my 89 fuses

I don’t have first-hand knowledge of the '89 models but I am going to say above the knees. There should be several relays mounted to a panel or bracket.

yes there is but only one that says radio not ac.

What are the colors of the wires going to the base of that relay?

Well here is tonight’s lack of progress, I have disconnected the ac compresser all relays over passenger side knees, all relays behind right side fuse box, #10 blows with the ignition off! I quit!

I also made certain that no bare wires were in contact with the door jambs.

Heres what I’ve got.

David …

So with the ignition turned off the #10 fuse blows just by plugging it in ? If this is the case that should narrow your search down considerably. Not that many circuits that are always hot off of the battery.

Actually, Groove, there are quite a few. If you look at Fig 1 in the wiring diagrams there are circuits numbered 54 through 67 (with #62 not used) that are supplied just by fuse 10 in the (always hot) right side fuse box.

David - looking at the picture of your right side fuse box, the fuses visible in the left hand column appear to be of the correct amperage. The right hand column, not so much - the 30 amp fuse does not appear to be correct for the position it is in. While this likely has no bearing on your current problem you should get that sorted to avoid problems with wiring or components getting fried.

EDIT: To follow up on the identification of the various circuits supplied by fuse #10, here is snip from Fig 1 for battery power distribution:

The ‘54’ within the square is what I referred to as circuit 54. To the right of that square, in the ‘squares with triangles attached to the right side’ are shown the other Figures (circuit diagrams) where the circuit appears, indicated within each diagram by a square containing the number of the circuit in question. For instance this is from Fig 7, Side Lights & Tail Lights:

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Mike …

Sorry, what I was a trying to get across was that when you consider ALL the electrical circuits in the car there are relatively few that are hot from the battery. Few enough that you can dramatically limit the scope of your troubleshooting.

Obviously something in one of those 13 circuits protected by the #10 fuse is grounding out. I’ve always had good success tracking something like this down with 2 long jumper wires and a multimeter.

Again this is assuming there isn’t a fault on the back of the circuit board itself.

Using the detailed electrical diagrams for the '89 XJ40 that’s available along with your excellent explanation of the symbology … as Sherlock Holmes would say “Come Watson, the games afoot”


Groove, I’m not trying to be argumentative here but for the sake of perspective - as shown in Fig 1, Battery Power Distribution, there are 77 circuits whereas in FIgure 2, Ignition Switched Power Distribution, there are 36 circuits so I submit there are 2+ times more ‘always hot’ circuits than ‘only-hot-when-the-ignition-is-on’ circuits.

And you are spot on with the use of the multimeter. It is an invaluable tool for troubleshooting electrical issues. In this case, I would probably start with checking the fuse holder for that #10 fuse. With battery connected but the fuse out there should be +12V (nominal, whatever battery voltage is) between the ‘hot’ side of the fuse holder and ground. There should be 0 volts, and NO CONTINUITY, between the negative (cold?) side of the fuse holder and ground. In David’s case, the suspicion is that there IS continuity between the negative side and ground, indicating one of the circuits supplied by that fuse #10 is shorting to ground. If that proves to be the case the next step is to determine which of the circuits is at fault. Because several of these circuits contain relays, pulling the relay in that circuit can isolate or eliminate (probably) the circuit as being at fault. For example, as shown in Fig 20, Heaters: Door Locks Etc., circuit 63 supplies power to the Door Lock Heater Relay. By checking the schedule of components (on the first of the two pages to Fig 20) we see the Relay–Door Lock Heater listed with the harness/wire notation LB84. Looking in the next section below Components we see in Connectors that LB84 goes to a Relay Base (Black) that is located in the Passenger Footwell, at the ‘A’ post. Referring to the photo David provided, there are three relays in the ‘A’ post area - one below the fuse panel. It has a blue base. There are two relays above the fuse panel but I cannot make out the bases. I assume one of them is black and would contain the relay for the door lock heaters. Pulling that relay would take the door lock thermostats / heaters out of the equation, so to speak. So, Watson, with those clues and as you, Groove, previously stated, “the game’s afoot!”

Here is my plan, 1 verify 12 v to 1 side of fuse with ignition off, 2 check other side of fuse to ground, should be no continuity, if there is stat pulling out relays etc. till I locate the fault. Make sense?

Sounds like a plan, keep us posted.

Since the average temp is 95 degrees the process may be slow.

Mike …

Now you’ve got my curiosity piqued.

There are appears to be 40 fuses between the left, right footwell, and center console (a suspiciously even number :thinking:) Not counting a few inline fuses and the mysterious “optional equipment” fuse panel that I know nothing about.

So my question is if I pull out the ignition key and extract each of those 40 fuses how many of them do you suppose still have power going to their circuits ? I really have no idea but I intend to find out :disguised_face:

Disclaimer … Do not become a retired pilot because this is the kind of thing you’ll end up doing !

And do not become a practicing accountant, well, for the same reason! :crazy_face: The answer to your question is: 34. All but the six fuses in the center console panel. I kid you not…it is pure math. :nerd_face: The old school kind, not the new math.

Where did you get the schematics from? I would love to have a set.

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I got them from the link Grooveman sent two days ago (post #10 in this thread).

That was the one I couldn’t open, have to fire up the old tower.

OK, Groove, inquiring minds want to know…:thinking:

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for those inquiring minds, #8 thru 17 on the right side are hot with no key in the ignition! I pulled all the interior fuses and plugged in the 20 amp and it didn’t blow, put all fuses back one at a time and fuse didn’t blow, a/c fans etc. all worked. hit the starter and pop! Since it was running I put a new 20 amp fuse in and it didn’t pop! Must be something with the starter circuit.