2005 XF Roadster, with loss of top and spoiler function. No. 7 fuse blows, before anything is turned on, including ignition. The paper inside the acc. Fusebox says that's the fuse for the "central control module" by which I think they mean the BCM. I find no short in the relay module box. Wiring to top motors and sensors looks ok, to gross check.

I'm afraid to just replace the BCM, because it seems there is a short to ground somewhere. Where should I look, or could a bad BCM blow the fuse. I have looked in the archive, but don't find anything about the fuse blowing with a BCM problem.

I'm a newbie here, and would like to thank everyone for their efforts. This is an amazing site, with a HUGE amount of valuable information. Thanks!!!

 

My manual calls that the fuse for "Electronic Transmission Control (Park / Reversing Lock) and BCM" (This is number 7 in the underhood fuse box on the driver's side.)

So, are you saying the fuse blows as soon as you put it in? Or, if not, just WHEN does it blow?

Sure sounds to me like a major failure in the BCM or transmissoin controls.

Headed to bed .... back on in the morning!

 

Yes, the fuse blows as soon as I hook up the battery, before I turn on the ignition, or push on the top or spoiler switches. That's why I was afraid of a short, and not just a BCM failure. I have driven the car several hundred miles, and the transmission seems to work OK. Now that I've found the fuse problem, I won't drive it until this is solved. I also did not want to just replace the BCM if there's a short somewhere, as I don't want to blow out a second one.

 

Well, it's a long shot, but you might pull all the cables off the BCM and try a fuse - if it blows, you know it's not the BCM.

If it does NOT blow, it may or may not be the BCM, as with the connectors unplugged, a fuse that refuses to blow could indicate a bad BCM OR that one of the disconnected wires has the fault in it.

But, again, it's worth a try. Try pulling all the connectors off the BCM and see what you have.

 

Thanks! I'm ashamed that I didn't think of that. The car is not where I am now, but I'm going up north again tomorrow night. I'll repost this weekend, after I get a chance to try it.

 

Ok, so I calmed down a little, and re-did everything.

The #7 fuse blows after the ignition is turned on, but before the car is started, or before any of the top or spoiler buttons is pushed.

If I take all the connections off the BCM, the fuse does not blow.

I don't have a DRB III computer analyzer, although buying one would probably be cheaper than going to the Chrysler dealer. I'm going to check all the leads to the BCM that I can with just a multi-tester, and referring to the service manual. I'll post again if I can solve it. Then, if not, I'll just have to spring for another BCM, I guess. I would not have thought that a BCM failure would blow the fuse, though.

 

I would check all the main power leads from the bcm to the fuse and all the grounds, and do an ohm test on them as well, it sounds like you have a major short either short to + or short to - the harness itself could be rubbing through to metal, a positive wire and a ground wire making connection in the worn out area, and check all your wiring around the fuse blocks for critter damage, just some ideal's.

 

Thanks! I did have a mouse nest underneath the relay fuse box this past winter. I did look for a bare wire in and around the box, and found one, which I repaired, but didn't help. Once the wires leave either the accessory fuse box or the relay fuse box, how can I follow them? They sort of disappear into formidable looking megacables.

 

By using a DMM and checking for continuity of the wires from the BCM connector to the fuse juction box and any other wire that goes to the same area, your are checking the wires from start to end for any breaks/open circut, and if grounded or shorted the DMM ohm's setting will show this.

 

Sounds like this won't be a case of "European automotive electronics" after all. (SOME people say that cars from over there are prone to electrical problems as they age - not ME of course, but SOME PEOPLE).

 

Thanks to all. This is going to take me some time. Please re check here in a couple of days, and I'll let you know what I find.