Alternator question

prpickett · 05-26-2011, 08:45 AM

I have a 1999 Dutchstar 38 ft and on a recent trip noticed voltage on the instrument panel staying around 12.5. It started raining (and eventually snowing) and voltage started dropping to around 12 and windshield wipers got slower. Suddenly (over the course of about 10-15 minutes) the voltage dropped to 8-10 volts and the engine shut off. I disconnected the tow, pulled the chassis batteries and took to NAPA. They said 1 battery was bad and the other showed recharge and test. I replaced both batteries, drove to the nearest campground and plugged in for the weekend. On Sunday, drove straight home (without blower, headlights, or wipers) and voltage showed 12.5 volts for the trip (4 hours). I am assuming that the alternator has gone bad since with the engine running and testing battery voltage directly with a voltmeter shows no increase from without the engine running, but is there possibly something else to check before I pull the alternator and order a new one? Thanks, Phil

smoker · 05-26-2011, 09:38 AM

I think that you will have solved your problem, when you put on the new alternator. I had the same problem with mine, and I was stuck in a city, where I didn't know where to go. Went to the nearest truck garage and had it check, and they said that it needed to be replaced, so after overnight and 615.00 bucks lighter, I was on my way.. not a good way to find out, that I could have done it myself, had I been home...
smoker

Arch Hoagland · 05-26-2011, 10:02 AM

Belt slipping on alternator???

**RJay** · 05-26-2011, 10:11 AM

It could be a bad voltage regulator but in the newer alternators it is internal to the alternator so a complete replacement is in order. The normal voltage output should be 14.5 volts. I would consider Arch's suggestion before ordering the alternator.

clubmed98 · 05-26-2011, 10:56 AM

RJay is correct but remember you can start gen set and run while driving and that will almost hold voltage so you can continue on trip with bad alt...

Triker56 · 05-26-2011, 11:26 AM

You might check for a alternator rebuild shop in the area.

The last one I replaced also only was putting out 12.5V by my VMSpc at idle or any RPM.

Mine was a 120 AMP and got it rebuilt for $138 and carry it as a spare.
Bought a 160 AMP new one for $208.65 to put on May 06.

prpickett · 05-26-2011, 12:04 PM

I checked for the belt slippage and that looks good, although I will replace the belts when I replace the alternator. I was looking around at the alternator and can't find any markings or label plate. Any ideas on how to ID it?

prpickett · 05-26-2011, 06:58 PM

Removed the alternator. Once I cleaned it up, I could see the data plate. 160 amp. A local shop can rebuild for $160 so that's probably the route I'll take. Anybody have any thoughts negative or positive on rebuild vs new?

Norm4015 · 05-26-2011, 08:34 PM

A rebuild is much cheaper than buying a new alternator. I vote for the rebuild.

Arch Hoagland · 05-26-2011, 11:13 PM

I suspect if you take it to a rebuild shop they will know exactly what it is. I'd do a rebuild on it also. That way you know what's going on with it.

And if you have to buy a new one I'd go to the original manufacturer.

Aftermarket alternators from Kragens, etc have given me enough problems to cause me to never buy components from them anymore. They'll give you another one when it dies but you still have all the hassel of installing it, etc

prpickett · 05-27-2011, 02:06 PM

Just got the alternator back from the repair place.The guy said it would have taken a week to get it apart for a rebuild due to rust. They replaced the brushes and said it was good to go. $55 out the door. I'll get it put back in today or tomorrow (waiting on new belts from NAPA) and keep my fingers crossed.

GaryKD · 05-27-2011, 02:23 PM

For future reference, if an alternator goes bad, one should be able to run the generator until you get to a place where further investigation can be made. The generator should keep the chassis batteries charged enough (or at least >12 VDC going into the circuit) to get you to your next destination.

popsuscdds · 05-27-2011, 03:03 PM

Greetings,
Be careful buying a rebuilt alternator. Some shops use too many questionable parts in a hurry to get them out the door. It took me three tries to get one that lasted. One rebuilt alternator installed in Alabama lasted about an hour(cost was $168.00). The second one from the same shop lasted 2,000 miles(cost was $193.00). The third one was new (costs $176.00) from a truck repair facility and is still going strong. This particular truck shop repair lots of log trucks. They don't use rebuilt alternators.
Have fun!
Milt