High Output Alt w/External Voltage Regulator

1998 XJ 4.0L
I just finished installing a large case 200A Denso alt and an external voltage regulator. It's the kit from alternatorparts.com. This was done because my PCM voltage regulator went out causing high voltage situation. I deciced to change the alt too, perhaps overkill, but I was getting the ext voltage reg kit anyway and my alt was original equipment.

I've run it and it now seems to be fine, 14.4v or so and steady charge, this changes a bit with load, but much better than the climbs up to 16v+ where I would need to shut it down.

I'm posting this to find anyone who may have done an external regulator like this, as I need to find a good solid source for battery 12v. The reg uses this both to feed the alt and as a sense line to determine the actual voltage at the battery in order to properly control the alternator output. I have looked in the PDC but hesitate to take power from places like fuel pump, ASD etc. An alternative would be to use one of these sort of sources to a relay connected directly to the battery. (By the way, the kit includes a Field Replacement Module that connects to the original wires to the PCM to fool the computer into seeing an alt and keeping the check light out.)

Any input would be appreciated.

I do not have a reply that will help you but,....it sound like a good idea,...something I would like to try. Do you have more information on this setup?

You can check the website alternatorparts.com or store.alternatorparts.com and he's on YouTube under alternatorman with some videos including one on the high output alt and external voltage regulator. I've decided that I will take a likely 12v source just to feed a relay connected directly at the battery. This will provide the regulator with the best voltage by which to determine alternator control. I'll see how this works going forward, the external regulator just seemed better than trying to open the PCM. It can be done, the voltage reg is on a separate board and some broken connections can be resoldered. It would not restore the regulator operation if it has fried components, but there is a documented problem with open or shorted connections at the jacks. I just figure that the voltage regulator should have always been a separate component to be routinely replaced as necessary. At least this aftermarket option is available.

Why not do something like a CS-130 or CS-144?

Anyway, we did an external regulator on the racer. The alternator/regulator combination is Chrysler based, and the regulator is a 70's-80's Dodge truck. The best place to "sense" is the bus at the fuse panel or distribution block. Find a keyed source there and use it.

I think I saw this some time ago on an online forum, maybe it was . I will have to do some research into this.

The charging voltage on my XJ is always below 13.5 volts except when the temperature is 50* or lower then it will get to 14.2 volt for a while. I need a constant 14.5 volt +/- .5 volt regardless of the temperature. The problem with my XJ I think is the battery temperature sensor which measures about 0.5 OHMS below specs. I have measured several others and they all are about equal to or lower than to one in the XJ. I disconnected it and ran the XJ only to have the ECM throw a tantrum.

techno1154 said:

I think I saw this some time ago on an online forum, maybe it was . I will have to do some research into this.

The charging voltage on my XJ is always below 13.5 volts except when the temperature is 50* or lower then it will get to 14.2 volt for a while. I need a constant 14.5 volt +/- .5 volt regardless of the temperature. The problem with my XJ I think is the battery temperature sensor which measures about 0.5 OHMS below specs. I have measured several others and they all are about equal to or lower than to one in the XJ. I disconnected it and ran the XJ only to have the ECM throw a tantrum.

Click to expand...

Why do you believe that you need constant 14.5 volts? The charge that your battery will take will vary based on temperature. As temps go up, your charge voltage will drop.

Read the temperature section here -
http://www.trojanbattery.com/tech-support/faq/

I'll ask again why do you believe you need 14.5v all the time?

DieselSJ said:

Why do you believe that you need constant 14.5 volts? The charge that your battery will take will vary based on temperature. As temps go up, your charge voltage will drop.

Read the temperature section here -
http://www.trojanbattery.com/tech-support/faq/

I'll ask again why do you believe you need 14.5v all the time?

Click to expand...

Thanks for the tip.

Those procedures are the same I am accustom to adhering to for backup batteries that are in use in a telephone system/network. The Optima battery in my XJ have different requirements.

http://www.optimabatteries.com/en-us/support/battery-care/charging/

techno1154 said:

Thanks for the tip.

Those procedures are the same I am accustom to adhering to for backup batteries that are in use in a telephone system/network. The Optima battery in my XJ have different requirements.

http://www.optimabatteries.com/en-us/support/battery-care/charging/

Click to expand...

Pretty much standard -

Recommended charging information:

Alternator: 13.65 to 15.0 volts, no amperage limit.

Click to expand...

After posting about my install of the 200A alternator, with the external voltage regulator, I felt it necessary to add information as it may not be working well for me now. It ran really well for a few days, maybe a week or so. I was getting 14.3V consistently with very small variations when running lights and mostly the heater/AC fan. It would drop into the high 13V range which is fine. However, the current problem started as I began to see a red flash on the dash. It was really quick and not until it got more prominent and stayed on longer could I see that it was the check engine light. I then checked for codes and have P0622 which is a short or open in the generator field circuit. OK, so this is where it applies to the mod I did with this alternator, as the two generator field connections now go to what they call a 'field replacement module' which may be a resistor in a heat sink or it may be more complex than that, but 'alternatorman' couldn't tell me exactly what it is. I get about 11.5 ohms across it now, no info on what it should be or if that's a useful measurement. Since it's the only component in the circuit now other than the voltage regulation within PCM, I'm looking at going backwards now and replacing the 200A with a stock 90A alternator and running it to the PCM again. Since I was getting high voltages before, I would expect that to reoccur. I have a new PCM in shipment now, and won't know until I try that to see if it's corrected. Since I could get no further info from the supplier, I felt it best to go stock until I determine where this issue comes from. All other sensors have been replaced and rechecked, with the exception of the speed, coolant, MAP sensors and I will be checking them before I change everything. Grounds done, with added higher capacity wires for that and battery. When I got the engine light, the problem quickly got worse where I limped it home missing and bucking. It restarts most of the time fine, but I drop it into drive and many times it will stall. Sometimes it will run but giving it gas it will die quickly. New NSS, fuel pump, CPS (a couple of times) TPS and most recently IAC. All Mopar electrical parts. New trans solenoids still measure good. Even though this problem is almost just like the past NSS or CPS issue I'm suspecting the alternator setup due to the P0622 code. I don't know if that leads to the PCM shutting down the engine through the ASD relay or not. (I do have to check the ASD and Fuel relays too) I know this post is kinda all over the place, but even though I'm looking for a solution other than a car cover for the whole winter, I felt I should say I can't recommend changing the alternator system from stock with this kit. Using this FRM is a workaround at best, and I've not found anyone that has been successfully using this method. If there is anyone that's using an external regulator on a later model (like 1998) XJ, I would certainly like to hear whatever your results were.