Alternator VS voltage regulator?

[Joshua13]

Hey Guys,
Been having a weird issue on my 2000. I moved to a colder town and it seems to be reeking havoc of the old girl. For reference about a 2year ago i upgraded all my cables (DIY jeepcables 7 cable bundle) I also bought their headlight harness back in dec. I am in Canada so i disconnected the DRL box. In Dec i also replaced the battery. The Alt is a refurbished one I bought when i did the cable upgrade ( see one of my previous posts) I also just replaced the power steering pump & tstat.

Now i have an issue where my voltage gauge keeps dropping to 9 volts and the gauge warning light comes on. She still starts every morning, but definitely low voltage when I'm driving (lights dim etc.) Now its only about 70% of the time, sometimes she runs just perfect. I am wondering how i diagnose whether it is the alt or the voltage regulator?

I have seen videos a long time ago, probably when i had the previous issue about installing a separate voltage regulator rather than changing the entire PCM, as that included getting the new one coded to your VIN.

any thoughts?

 

[Bent]

As I recall, the voltage regulator is an integral part of the alternator. The XJ is way past the point of a generator and separate voltage regulator.

 

[75SV1]

I think there is a kit to change over to an external unit. More like the old Fords.

 

[lawsoncl]

On a 2000, the voltage regulation is done by the PCM. Have you verified that the belt is correctly tightened? You can test to see if the alternator is getting commanded to produce power with a meter. Refurbished quality isn't that great, btw. If it's got a warranty, I'd replace the alternator before trying to jerry-rig something that may not work anyway.

 

[75SV1]

Here's the kit I just ordered off of EBay:

1991- 2005 JEEP ECU VOLTAGE REGULATOR BYPASS KIT, H D ADJUSTABLE, 14.3V PRESET | eBay

Alternatorman is the original developer of this kit for Chrysler, Dodge, and Jeep vehicles. With our system, not only do you get printed instruction, you also receive our exclusive ALTERNATORMAN TECH HELP.

www.ebay.com

 

[lawsoncl]

Using this kit will likely cause a check engine light. Before you go that route, I highly recommend testing the alternator and confirming that the belt isn't slipping. There are some instructions in that eBay ad for a quick and dirty test to confirm the alternator is working, but a real load test will tell you if it's weak.

 

[75SV1]

I'm just experimenting. I did have my alternator rebuilt last year or so. I do have a bad short somewhere. I think I pinched a wire when installing my mini stroker.

 

[Joshua13]

Hi All,
just so you know i replaced the alternator and it seemed to solve the problem. I am about to post anew thread due to a new issues that may or may not be related

 

[75SV1]

thanks for the update. I did get that kit. It has some type of 'resistor or such. Referred to as FRM in the instructions. Its the gold cylinder with fins. It is suppose to cover for the ECM not throwing a code. Instructions also say, the EMC might throw a code at times with the FRM at times. I might use the kit if I go with a GC ZJ alternator.

 

[lawsoncl]

I believe the resistor in the kit would go between battery positive and the control wire from the ECM to emulate having the field coil connected.

The ECM will throw a code if it doesn't see battery voltage on it's control wire when it's not grounding that wire, which would indicate the field coil is broken. It would also throw a code if the driver in the ECM were blown and it didn't see the voltage on the control wire pulled down when it tried to ground it. So the resistor is only going to trick the ECM if the ECM isn't broken.