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LJJSRZ · 02-21-2014, 06:46 PM

cummins replaced a alternator/regulator with a used one. The original unit overcharged and undercharged. The new alternator continued to overcharge also. I went to another Cummins dealer who replaced the alternator/regulator with a brand new unit. The unit STILL overcharges. The Cummins tech has tried all sorts of checks, but can't understand why the alternator is overcharging. The chassis batteries are sealed and about 3-4 years old.

bluepill · 02-21-2014, 06:53 PM

What is happening that makes you think that the system is overcharging? Is the voltage too high?

A bad battery or connections can also cause charging problems. If the voltage is over 14.8 volts, try disconnecting the batteries and substitute a known good battery from another vehicle and see what happens. You can do this with jumper cables. Be sure that the jumper connections are clean and tight.

LJJSRZ · 02-21-2014, 07:04 PM

:The voltage is above the 14.4 v, and the alarm lite is coming on.

gemini5362 · 02-21-2014, 09:02 PM

check all the grounds

DonL · 02-21-2014, 09:33 PM

We had a similar problem with our 96 Holiday Rambler Imperial. Charging voltage was around 15 volts and the battery light would flash. It only went out when I put a load on it with headlights, heater motor,etc. Records showed that the previous (original) owner had replaced or repaired the alternator seven times at a cost of more than three thousand dollars. The alternator is a Leece Neville, internal regulator with external excitation.

After chasing several wrong theories, I found that the alternator input from ignition (excitation) was hot all the time while the battery lead (voltage sensing) was hot only with the ignition switch on. The installed condition was in accordance with color coding according to wiring schematics provided by Spartan. It turns out that the leads were mistakenly grafted inside of the wiring harness. Switching the leads fixed the problem.

I don't know what your coach is, but if chassis is Spartan it might be worth checking. If you need to swap the leads, be careful. It is easy to mess up the terminal posts on the back side of the alternator (and I'm not saying how I know). Good luck. Let me know if I can help.

Don

Randy125 · 02-22-2014, 08:20 AM

I had a similar problem in 2012 tuned out to be corrosion on the sensing wire connection. Good luck.

jauguston · 02-22-2014, 08:32 AM

A charge voltage over 14.4v is normal. Modern automotive electrical systems have typical peak charge voltages ranging from 14.8v to over 15v. If you get a alarm at over 14.4v the problem is with the alarm not the charging system.