Does the ground wire go from the dump load module to the D+ terminal? Is there a second ground wire on the D+ to the body? I just can't find this information, it seems simple, but, I can't get my alternator hooked up right. Thanks in advance.

 

What XJS?

 

What ground wire?




According to my diagrams (same as you saw in the previous thread) there should be 3 wires at the back of your alternator: the big output wire, the exciter wire, and the load dump wire. The exciter wire and the load dump wire go to the same terminal on the back of the alternator.

The second wire of load dump module goes to ground....but I don't know the exact location of the ground point. Is that what you're trying to find out?

The alternator itself is grounded via the mounting brackets. There isn't an alternator ground wire, if that's what you were thinking

Cheers
DD

 

Doug, thanks for laying that out, I'm sorry I seem so stupid, but 2 other people started pulling wires off, and, attaching them, when I first pulled the car into the garage 2 months ago. Yes, I saw the diagram, it was a big help. For some reason, we have it all attached the way you say, PLUS a ground wire from D+ to the same ground point as the dump load module. So, all I need to do is get rid of that extra ground wire, then check it out. I think we bypassed the dump load module, and, emergency grounded the alternator when we were trying to get it started. This is encouraging, I am going up to the garage this evening, I will get rid of the extra ground wire! Thanks, again.

 

A couple more tidbits from some of my postings (elsewhere on the internet) from a few years ago.

The dump module ground wire grounds at the upper radiator mounting panel. The sheated wire from the module is the one that goes to the alternator.

Also, some have reported simply leaving the dump module disconnected if found to be faulty, or even suspected of being faulty.

It's safety device to prevent voltage spikes if the battery (for whatever odd reason) becomes disconnected with the engine running.

Cheers
DD

 

Doug, it works!!!!!!!!! I took the extra ground wire off, and, the alternator is charging the battery. The idiot light is off!!!!!! I am elated, the car is ready to roll. Thanks for your help!!!!!! Ed

 

Doug,

I have the same issue right now with mine vehicle. Your reference to disconnecting the module sparks some interest with me.

I thought the module reverts all voltage spikes to ground, not just when the battery becomes disconnected. I realize Jaguar engineers did a poor job of providing a comprehensive description of the functionality of the module. (I have both the JDHT CDRom and a hard copy set of the mechanics manuals.)

From what I have researched on Jag-Lovers web site, I found a few posts describing a method of rebuilding the module by replacing the Zener diodes. I just got them in the mail yesterday and plan on doing the replacement in the next few days.

I understand this is an XJS thread, but looking over the diagram from the other posting my XJ6 layout is the same for the alternator, starter, module and battery.

Do you think it's a good idea to bypass the module?

 

Maybe it does



Could be.

My recollection is that the ECU is internally protected up to 30 or 40 volts. I think the idea is that disconnecting the battery is the only thing that's likely to cause a spike greater than 30 or 40 volts.....so the function of the dump module is simply described as 'to protect against voltage spikes if the battery is disconnected'.

<shrug>

If the Jag manuals are vague or even outright incorrect it wouldn't be the first time




Over the years I know that (at least) a few guys have disconnected theirs and reported to ill results, perhaps because they've never disconnected the battery with the engine running! But, if the module is working....or in your case can be repaired to work....I'd leave it hooked up. I don't see the point of summarily eliminating a protection device just for the heck of it.

Cheers
DD

 

Hmm. Im reading thru this trying to figure out the role, function and - whether mine is even functioning - what happens if the little module is not functioning or malfunctioning...? I will keep on reading but I am wondering if folks have any further thoughts or learning on this dump module?

I have a thread having to do with a strange kind of out of the blue voltage drops,,, sometimes while driving at highways speeds,,, and clicking nothing ON or OFF in the cabin to cause the voltage change/drop. The voltage will drop way down into the 11's - drift there - and then pop righ back up to "normal". I dont like it... I have doubled my efforts a bit in cleaning the connections at the positive feeds at the fire wall on both sides, all of my positive light connections front and back which did produce a slight improvement - slight. Im wondering about this module that shares a post off the alternator - with what seems to be a wire that feeds the volt gauge on the dash. Looking at the attached pic,,, well - I dont know if I like that wire to ground especially if I dont know if the DUMP module is working properly.