My Experience with Duvac Alternator

[Mike Grevers]

Not to change the topic, I have a DUVAC system on my coach as well. The old alternator's terminals corroded so badly that it had to be replaced. I found a unit for $350 +/- on amazon and installed it. I have now had to replace it 3 years in a row and the alternator shop says they are not worth rebuilding. They say the original DUVAC can be had for $1500 and they last a long time.

Moral of the story: If you still have your old one and decided to go for a cost effective replacement like I did, definitely send the old one out for a rebuild. I now drive with a second aftermarket alternator under the coach for when it needs to be changed out again.

[Mark Nagy]

I wish I did keep it.  At the time I did not think it could be a problem down the road. It only had 18,000 miles on it since the coach was new.

[Bill Lampkin]

My Duvac alternator failed two years ago just as we started our summer trip. I found an alternator shop in Eugene Or; he had a rebuilt one in stock, $150.

[Mike Grevers]

I noted that my alternator would fail after high loads. Example: you drive down the road and your wife is making drip coffee. You see your voltage drop from 14.3 to 12.8 and very slowly recover when the pot is turned off. Or run the toaster/microwave. You have to remember your alternator is also charging the house batteries and thereby the inverter so keep that in mind when running down the road.

Also, I thought starting the generator would help in these circumstances. However, when you have the coach engine running and start the generator the load is put on the alternator creating high load; especially in cold weather when it takes much more current to start. I have gotten into the habit of starting the generator on shore power then starting the engine and then shutting the generator off when the coffee is hot, toast is toasted, and the microwave is off.

[Fred Brooks]

   Mike,
I would like to make one suggestion to your procedure. In the summertime you may have your air conditioners running as well as other loads while on shore power. These loads could well exceed 30 to 40 amps. When you start the generator there is a 30 second time delay and the transfer relay engages. When that happens, you are transferring that entire load thru the transfer relays contacts. This can cause premature failure due to arcing. An indicator that this may be an issue is the transfer relay may start to hum or buzz due to poor connection on the contacts. Safe protocol is to turn off the loads first.
Fred

[Mike Grevers]

That makes sense. I haven't had an issue but your right that the full load hits that contact at once. Most air conditioners should have a time delay to restart the compressor to prevent lockup but I don't know if that is the same for RV A/Cs. Also by starting the generator on shore power the transfer switch should go directly from shore power to generator when the shore power is unplugged no? I don't know that there is an open position for this switch in the middle that would allow any appliances to stop operating.

[Fred Brooks]

  Mike, you are correct concerning the roof air conditioners. Duo-Therm (Dometic) have the 180 second delay that engages the compressor after the blower fans see 120volts. Happy New Year and Happy Trails to you! Fred