Need Help. Friday, the power fuse for the bpm fuse blew after going down a steep driveway (20 deg.). This is F7 in the driver bos (15A). it powers the bpm which powers the shifter interlock, interior lights, washer pump, one of the horns, etc. I replaced the fuse after diagnosing and it worked fine for a day and then it blew again. Now the fuse blows as soon as i replace it (key on or off). Any ideas on how i can find out what is blowing the fuse? Any help would be very appreciated.

please note I have the electrical schematics for the car which is a 97 XK8, but I am new to Jags as i just bought this car the day before this problem.

Thanks in advance.

 

hmmm, sounds like water somewhere...especially after going downhill (water went down there with it!)

Better get looking for puddles, check boot (take the spare out), bonnet, everwhere...and report back.

Added- make sure your spare tire didn't go slamming into that module right in front of it. Not sure what it is...but there's one there.

 

H20boy, After i wrote the post, I went and checked the spare and tools as i have heard a clunk every few times i have gone up or down my driveway, but it and the tools, were very securely in place and no visable movement. I did not note any controls in front of the tire, but there is a wire harness loose behind the tire (i think it is the rear tail lights. I can see your point on water, but i would very much doubt it as i know the car had not been wet in several weeks, unless it came from the air con. Any ideas how i could trouble shoot. I was hoping the BPM had separate plug on it so i could disconnect things and ohm out, but no such luck, it is one big plug.

Thanks for your replies

 

If not a direct short due to water, it must be a grounded power somewhere. I'm trying to think how I would approach this.

Do you have your 1997 wiring diagrams? If not, try the links in the FAQ thread located at the top of the XK8/R forum. If not, I may be able to email it to you. Also, if you don't have the JTIS CD, go to the download on this forum and make your very own, it helps out a TON.

Find out every system that is on that fuse, and begin eliminating (disconnecting) every single one of them in succession, testing the jumper as you go, looking for the one that doesn't activate your test light.

Or you could find the BPM, but that's drastic right now. I've not heard of any BPMs that went bad...ECMs, ABSs, sure...but not the BPM, that I can recall.

 

Isolating the suspected output of the BPM is rather difficult. In the past I have floated individual line in the connectors with a very small paper wedge cut from card stock. But the location of the module and type of connector has to be correct.

Another method is to disconnect the harness-to-harness connectors
Example: 14.1 (your washer pump)
To the right of the BPM it show all lines to the pump and relays going through two
connectors LF1 and LF60.

At the very end of the wiring Diagrams is a section (indexed by diag. number) that
will give you the location of the connector, line levels, grounds, relay location.

The harness-to-harness connectors are sometime in difficult locations. (A pillar)
or easy locations (under center console)

Checkout the cable you say is loose in the trunk.
The cable between the tire and the rear of the car is for for the tail lights
as you stated. It should be tucked in a channel across the back, and not visible.

That "module" forward of the spare are the main fuses. The really big ones....

Also check the Lamp control module. It is in (or under) the trunk fuse box i believe.
It seems to move around year to year. By Checking I mean worn or frayed insulation.

Start by disconnection the BPM and see if the fuse blows. Just in case the problem
is before the BPM.

Unless you have a cheap source of fuses, I would use a pop-out circuit breaker when working on this problem. I have used a blown fuse and soldered two 24 inch wires to the fuse,( one on each side of the blown link). Connect a circuit breaker (Radio Shack?) of the appropriate size to the end. Just make sure it has a visible indication that it blew.


Older Jags are easy.
Just replace fuse with a 3/16 by 1 inch brass rod, and look for smoke.

 

Fred, you're an electrical genius. enjoy -->

 

After a good deal of contemplation, I found that the wires to the driver sun visor had the insulation cut and were shorted to the frame. Once fixed and the fuse replaced, all is well with this circuit.

Thanks for your responces to this post. I am sure that i will seek more help and advice as I attempt to bring the car back to perfect.

 

visor light... i would have never thought to look there!