I have just replaced my second alternator in seven years (50k miles).I have occasionally run the fridge on invertor while driving at high altitudes. The 425 watt heaters should draw about 45amps at 12 volts. Adding 10 to 15 amps for chassis demands total altrnatorload should be 60+-. The alternator on the cat diesel is supposedly rated to 160amps.Am I expecting too much from the altrnator?What are others experiences with this?Thanks for the feedback.Bob

You model unless I am reading wrong is AC for the heater You get better cooling with gas. Your inverter also draws. But to answer your question unless your inverter is drawing too much then no unless you are near the max draw all the time. I figure around 5 amp plus what the inverter draws.

The refer elements do NOT draw 12 volt DC power. 1200 models have 2 AC elements and they pull 1.7 amps AC EACH for a draw of 3.4 amps AC. That is 408 WATTS AC . Your Inverter has MORE than enough power to run the AC elements and it will not cause failures of Alternators. If you have premature failure of Alternators, something else is causing it. 7 years and 50k sounds like a good run for an Alternator on a Diesel motorhome. Doug

The two previous posters seem confused in that you're talking about your inverter draw to run the refer heater on AC provided by the inverter.My experience is to run the refer on gas.

I assume "2nd alternator in 7 yr 50k" includes oem and two replacements. That does seem excessive.Only way I know to really check would be to get an ammeter on the alternator to monitor output while in transit. But really I would just let the fridge run on propane.

Hi,Look into the duty cycle of the alternator. In the past I'd run heavy loads such as the water heater, but I used a 1/3 duty cycle (i.e. 20 minutes on, and 40 minutes off).

Running norcild 1200 off the alternator | Good Sam Community

MountainAir05
Explorer II
May 30, 2020
You model unless I am reading wrong is AC for the heater You get better cooling with gas. Your inverter also draws. But to answer your question unless your inverter is drawing too much then no unless you are near the max draw all the time. I figure around 5 amp plus what the inverter draws.
dougrainer
Nomad
May 30, 2020
The refer elements do NOT draw 12 volt DC power. 1200 models have 2 AC elements and they pull 1.7 amps AC EACH for a draw of 3.4 amps AC. That is 408 WATTS AC . Your Inverter has MORE than enough power to run the AC elements and it will not cause failures of Alternators. If you have premature failure of Alternators, something else is causing it. 7 years and 50k sounds like a good run for an Alternator on a Diesel motorhome. Doug
2oldman
Explorer II
May 30, 2020
The two previous posters seem confused in that you're talking about your inverter draw to run the refer heater on AC provided by the inverter.

My experience is to run the refer on gas.
time2roll
Nomad
May 30, 2020
I assume "2nd alternator in 7 yr 50k" includes oem and two replacements. That does seem excessive.

Only way I know to really check would be to get an ammeter on the alternator to monitor output while in transit. But really I would just let the fridge run on propane.
pianotuna
Nomad III
May 30, 2020
Hi,

Look into the duty cycle of the alternator. In the past I'd run heavy loads such as the water heater, but I used a 1/3 duty cycle (i.e. 20 minutes on, and 40 minutes off).
GordonThree
Explorer
May 30, 2020
Do you have room on the motor to mount a second alternator? Leave the OEM alternator alone for running its intended loads, and a second high duty-cycle alternator for charging the house batteries and powering the inverter?
grldst
Explorer
May 31, 2020
Likely you have a Leece Neville alternator. Not the best for running long periods with a heavy amp load. I don't do it with that alternator because I have heard from others of having the same problem as you when trying to run the Fridge on AC.
Stim
Explorer
May 31, 2020
What failed on the alternator?
That's where I would start, they are pretty simple and the failure might point to the problem.
islandvagabonds
Explorer
May 31, 2020
Thanks for all the feedback.
I tried running the fridge on gas while driving above 5500 feet and it did not cool well so I switched to AC as the manual recmmends. It was a bit cooler but not as good as my old 1200. This is a brand new 1210. The old one had a six year Amish unit that nearly burned up my coach. I know I should have gone with a residential unit.
By the way the alternator did not fail while operating on ac while driving.
theoldwizard1
Explorer II
May 31, 2020
islandvagabonds wrote:
I have occasionally run the fridge on inverter while driving at high altitudes. The 425 watt heaters should draw about 45amps at 12 volts. Adding 10 to 15 amps for chassis demands total altrnatorload should be 60+-. The alternator on the cat diesel is supposedly rated to 160amps.

No that alternator should handle it just fine.

Why did you come to the conclusion the alternator is bad ? Low voltage ? If so, it is either the diodes of the voltage regulator inside of the alternator. If you are handy enough to replace and alternator, you are handy enough to replace the voltage regulator.

The rest of the major parts (bearing, slip rings, brushes, windings) in an alternator last a long, LONG.