Aftermarket 24V alt voltage low

[Crawdaddy]

I used TM America's brackets to do the dual alternator setup with the delco alternators. The install went reasonably well and the 12 volt alternator is doing great. The 24 volt alternator....not so much. It seems to give me a couple issues.

First issue is when I first start up the truck, the alternator doesn't start producing power. No big deal, once I bump the throttle a little bit, it looks like it gets enough speed up to self-excite itself and start producing. No big deal. However, after it starts producing, regardless of engine RPM it won't build the RPM over 25 volts. 25 volts is above the batteries' resting voltage so it charges, just slowly. Also, as a result, the voltage meter never shows green, just below the tick to get into green. This alternator doesn't appear to have any adjustment to it.

Where should I go with this? Should I just let it be since it is charging?

 

[doghead]

Detail of the alternator you choose would help.

It sounds like your new alt has a 25 volt regulator set point.

The stock deuce alt is 28 volt

 

[Crawdaddy]

I didn't post the part number because TM America only sent me the part number after paying. With his blessing, I'll post it. It is a delco cased alternator from what I understand that was used in agricultural applications.

 

[doghead]

Well, without specific details, your issue cannot be answered 100% correctly.

I'm fairly confident what I already posted, are the facts.

 

[Stalwart]

Are you using a REAL voltmeter or you relying on that old thing in the dash? Try getting volt reading at both the batteries and the back of the alternator when it is running, that will help in the diagnosis.

 

[Crawdaddy]

25 volts using my multimeter at both the batteries and alternator. It's definitely seeming like it's a 25 volt regulated alternator. It's lester part number 7197.

 

[Stalwart]

If the batteries are significantly discharged the alternator may be working very hard and cannot yet reach 28 volts until the batteries are better charged. I've never seen an alternator's regulator set so low and remember it's only a 65A unit. I'd charge the batteries and try voltage tests again.

 

[doghead]

He has a 24 volt alternator now.

If you get 28v or more form a 24 volt alternator, you have a problem.

 

[Stalwart]

He has a 24 volt alternator now.

If you get 28v or more form a 24 volt alternator, you have a problem.

Sorry boss, not quite true, some batteries are fine with slightly higher voltages and I've heard acceptable levels as high as 29.6V. In school we learned as a lead-acid rule, 13.7-14.1 volts per 12V battery is considered nominal. That would be 27.4-28.2 for 2 in series.

 

[doghead]

I didn't say he has a battery problem, or a problem at all. Just the fact is, he no longer has a 28 volt alternator. He has a 24v alt now.