91.5 Low Charging Voltage

[ro23j]

I know this subject has been beat to death but I tried everything I could read on here on this subject and still can't resolve the problem.

I had previously bypassed the PCM with a relay supplying battery voltage to the regulator and alternator. This bypass worked and I had no problems until the starter failed and I tried to jump start the truck. The low voltage condition started after I replaced the starter.

I have tested and or replaced the following:

-New alternator - tested twice by 2 shops and is good. I did the full field test myself to confirm.
-New battery
-New starter
-Two different regulators, one is adjustable and was tested and set at the recommended resistance.
-I put on a new regulator connector and ran a new green wire from the regulator to the alternator. I also have a separate ground wire from the regulator case to the negative battery post.
- As a test, I ran a separate fused 6 ga wire from positive battery terminal to battery connection on alternator and it made no difference.
-I have checked fuses and fusible links, which seem to be ok.

With the key on, I have battery voltage at the regulator, field connection at talternator and battery connection at alternator. The truck starts fine and when running, there is 12.04 volts at the battery.

Any thoughts or ideas are welcomed and appreciated.

Thanks, Jim

 

[ro23j]

UPDATE: I just got a new regulator from NAPA and it is now charging @ 14.8 volts. Hopefully, it will continue to function and I will get a spare (and throw away the "good" ones that I had).

 

[sdeeter19555]

Is your voltage steady?

I just had a vr fail, the replacement AC Delco vr pulses. I put a 20 year old rusted junk vr on and it's steady. Hearing a lot of the newer vr pulse, why I asked...pass a Napa every day

 

[ro23j]

Is your voltage steady?

I just had a vr fail, the replacement AC Delco vr pulses. I put a 20 year old rusted junk vr on and it's steady. Hearing a lot of the newer vr pulse, why I asked...pass a Napa every day

I had a digital voltmeter on the battery for a few minutes but did not drive the truck. I will report back after an extended drive.

 

[Wayne M.]

Hey Super Stock Belvedere what year is your truck? Can you make a little signature line to appear in your posts? It’ll better help us help you.
Do you really have a RO car?

 

[sdeeter19555]

I had a digital voltmeter on the battery for a few minutes but did not drive the truck. I will report back after an extended drive.

Mine you can watch on the dash gauge...a digital is dampened (I have one mounted) and it holds fairly steady. My dash gauge pulses between the mid and high mid lines on the gauge...

 

[ro23j]

Hey Super Stock Belvedere what year is your truck? Can you make a little signature line to appear in your posts? It’ll better help us help you.
Do you really have a RO car?

The signature line that I can see shows the year and model of both of my trucks. And yes, I have a RO car.

 

[sdeeter19555]

My old 20 year old VR...

 

[ro23j]

My old 20 year old VR...

I like the shield that you installed. I just moved mine to the driver's side inner fender to make it easier to access / replace.

 

[sdeeter19555]

I like the shield that you installed. I just moved mine to the driver's side inner fender to make it easier to access / replace.

Someone mentioned moving it...that is an option down the road (maybe this spring when it's warmer)...

 

[Wayne M.]

Ok I see it jim, sorry.
Do your trucks have a ammeter or a voltmeter on the dash? Originally.

 

[ro23j]

Ok I see it jim, sorry.
Do your trucks have a ammeter or a voltmeter on the dash? Originally.

It has a voltmeter and it is actually reading very close to the hand held digital voltmeter that I use across the battery.

 

[Wayne M.]

I had a 92, and it had a voltmeter. It also had the SBEC PCM inside the left fender near the battery. Do you have that? I don’t recall it having a old style VR though.

 

[ro23j]

I had a 92, and it had a voltmeter. It also had the SBEC PCM inside the left fender near the battery. Do you have that? I don’t recall it having a old style VR though.

Mine is a 91.5 with intercooler. It has a PCM but also has the external regulator. My understanding is that 92 was the start of alternator with voltage controlled by the PCM.

 

[Wayne M.]

If it’s anything like the 92, you need a crank speed for it to start charging. Is the VR energized by the PCM? I had a tach on mine and I never had a problem with that. mine used to loose speed signal and drop out of OD.

 

[ro23j]

If it’s anything like the 92, you need a crank speed for it to start charging. Is the VR energized by the PCM? I had a tach on mine and I never had a problem with that. mine used to loose speed signal and drop out of OD.

The 91.5 and prior did not have a crank speed sensor and I don't think the VR voltage is controlled by the PCM. But I learned when I had overcharging problems, that there is a splice in the wires that provide power to the VR and alternator that can be source of voltage problems. I learned from a thread on here that you can bypass the splice with a relay and it worked for me.

 

[Wayne M.]

So I went back and reread everything, and it sounds like you’ve got it kicking good. I really thought when the intercooler came (91.5), so did the computer control. Thanks for clarifying that.

 

[mysteryman]

You should read my posts on v/r's and how to solve the problems your having . I do have the correct v/r's and they are adjustable

 

[ro23j]

I can provide a good reference for the adjustable regulators that mysteryman sells. I bought one from him years ago and it solved my previous overcharging problem and gave me years of trouble free service.

In hindsight, I probably should have just bought a new one from him when my most recent problem (undercharging) first showed up. That would have saved me a lot of testing, buying new parts, etc.