Had a couple times this week where volt meter was low, not showing a charge. After a stop and restart, showed normal. Took it by O'Reilly and everything checked out good.

Today same problem and it was still showing low and caught it with the test at O'Reilly, bad regulator.

So, in all my brilliance I decided to check the alternator wire. Arced the wrench off something and almost welded it. Blew the fusible link.

Parts stores don't know what a fusible link is these days an they don't carry 12 gauge, the ones open Sunday anyway. Got a 100 amp mega fuse from O'Reilly. Do I need to replace that with something smaller?

And the alternator didn't show charging the short 4 miles in traffic to O'Reilly with dead fusible link. However, shortly after replacing it with fuse, it came back up to normal charging.

Is the voltage regulator in the alternator about to die for good, or is it something else that needs checked?

 

The voltage regulator is part of the PCM, not the alternator. That's about all I know about it.

 

Then I wonder what the O'Reilly clerk thought they were reading when they concluded it was the alternator/voltage regulator?
Standard response when they don't detect alternator output?

 

Remove the alternator and have it tested...

If it is good, then my situation lead to a defective cam sensor that intermittently threw out a bad signal that the PCM didn't like and my voltage dropped to 9 volts....

I also had intermittent "miss" at cruise speeds....just a quick hesitation....like some flipped on on off switch...

Hope this helps

 

unfortunately you will find the alternator regulation (and injector & spark grounding) is handled inside the PCM by individual circuits containing Mosfets and Capacitors

these components eventually fail, and leave you without vital functions

if this is your issue, an external regulator circuit can be cobbled together (search this forum)

otherwise another PCM would be needed, but you need to exclude other possible causes, bad connections/corrossion and Alt faults

 

The last time I tried to remove one was about 10 years ago, and I ended up taking it to a shop to replace. However, I am not as rusty now as I was then.

How did you nail your problem to the cam sensor? BTW, I am not getting any codes other than the usual downstream O2 sensor.

 

If it seems to be OK I'd let it be.
But the one thing I am wondering about.
How many amps is your alternator?
My understanding is you use the mega fuse that is just higher then the alternator output.
In my Jeep the alternator is a 117 amp one. So I used a 125 amp mega fuse.
When I get my 155 amp alternator in next spring will change that to a 175 amp mega fuse.

 

That alternator has been replaced at least once and it is supposed to be stock output for a 1996 XJ 242. And I just looked at that PDC diagram that I've posted a few times already and it has a 125A fuse in that position. So I guess I am upping it to 125.

Might not be a bad idea to start working on the external regulator mod too.

Edit: All the parts store replacements say it is a 90 amp alternator.

 

Wondering if one of these voltage regulators for a 1991 Jeep might be a better choice than the ones from a Dodge truck?
https://www.oreillyauto.com/shop/b/c...tage+regulator

Dodge version, which seems identical to my 72 Charger
https://www.oreillyauto.com/shop/b/c...tage+regulator

 

Well if it is a 90 amp alternator I'm thinking you are good with the 100 amp mega fuse then.

 

When researching putting in a higher amp alternator the rule appears to be a mega fuse just over the
output of the alternator.
Since they only come in increments of 25 you go to one just higher then your alternator.
For a 90 amp thinking 100.
For my 117 I used the 125.
My guy who rebuilt a factory alternator and upped the amps for me said it is now at about 155.
So that is why I am going to use a 175. Remember they only come in increments of 25.
But thinking I could probably use a 150 if I wanted too.
Cause it is so close.
But..... LOL.

 

I keep back up sensors for "just in case" and my thought process was to swap out the cam sensor first then the crank sensor. After that was a new coil and wires as I thought it was an ignition issue and not a fuel issue. After swapping out the cam sensor the issue has not surfaced again. I also did not get any codes from the PCM.
hope this helps

 

Had no problem on the first leg of my trip to work, about 6 min and full operating temp before shutting off engine.
Then after picking up coffee etc., restarted with no charging. Drove back home and was going to call out of work and it started charging about the time I got to my driveway. GEN light stayed on until I did a restart. Gauge went to normal zone. Went to work and looked like a fully charged battery when I got there.

First thing, that I should have done before, is take off that connector and polish up those terminals, clean with WD-40 Contact Cleaner (already got the B terminal), grease. See how she runs on the way to O'Reilly and get the voltage regulator, connector/pigtail, maybe some extra wire, a 125 amp Mega Fuse, and see about bypassing that computer when I get home.

Searched online last night for which fuse sockets in the PDC are switched through the key switch, but the diagrams I saw look like the answer is none. I have plenty of empty fuse sockets in the cabin anyway, will use one of those I suppose.

Should be about 14 AWG wire or thinner coming out of this pigtail:
https://www.oreillyauto.com/detail/b.../s573/5820223/

From the tutorials and kit instructions I watched, it is keyed power to the center pin, then the pinout doesn't matter when it gets to the alternator. But a ground should be run from alternator case back to the voltage regulator case. Probably mounting the regulator high on the firewall passenger side.

Hoping I am not bypassing the gauge, and also that I won't need one of those computer trickers (Field Replacement Module), but from the descriptions I might not be able to get around that: https://store.alternatorparts.com/fr...nt-module.aspx

 

Checking alternator off the vehicle?

Since this is an intermittent issue, I'm not sure if bench testing it will catch anything that the on-vehicle magic box test didn't catch when it was not charging yesterday.

 

Here is a question...when your gauge goes low...does it read much lower than battery volt...should never read much lower than 11. If it does its a bad gauge. 2ndly you can get almost any size wire from a boat store like west marine