Community Forums

Terry W · 09-29-2015, 06:42 AM

How big a deal is it to remove the alternator? Is it a one man job? I want to yank it out and get it tested.

If you've read some of my recent posts you probably remember I had it replaced a couple of weeks ago. I believe there may be an issue so I want to have it bench tested to make sure things are as they should be.

Pretty mechanical and I have the necessary tools.

Thanks, Terry

wolfe10 · 09-29-2015, 07:01 AM

Terry,

Not difficult if you are "pretty mechanical".

Be sure to CAREFULLY remove the wires, label them and insulate them (I use an old bicycle inner tube cut into 6" lengths to slip over connections and tape in place).

Then use a rachet to detension the belt tensioner so you can remove the belt.

Then physically remove the alternator. If you have never done this before, take some pictures.

Assume you have done troubleshooting in place and verified that the alternator indeed is bad.

Terry W · 09-29-2015, 07:59 AM

Thanks Brett,

I'll get it pulled. I had it replaced a couple weeks ago and on our way home a week and a half later I got a check eng light and the volt reading was over 16 volts. I had been running for a couple of hours with cc on at a steady 60mph when the light lit. I turned off cc and raised and lowered the rev and things went back to normal. This happened a couple times while using cc, but not during normal driving in traffic with the usual variations in speed.

It seems too coincidental. The alternator has 12 mo/12k warranty and I've already contacted the installing shop, 650 miles away, they are onboard with getting it tested.

There is a very reputable local shop that will test it and give me their opinion.

Terry

ahicks · 09-29-2015, 08:32 AM

Maybe just me, but prior to removing an alternator that's just been replaced for "testing" purposes, I think I might be focused on coming up with ways to accurately troubleshoot the charging system.

Terry W · 09-29-2015, 08:43 AM

I am thinking I should start with the last thing changed. Eliminate the alternator and go from there. If it tests good then I'll have to regroup and do some brain picking on here. It's hard to find an intermittent problem, I don't know of a way to recreate the over charge situation. Like I said it happened 2 or 3 times after extended runs on cc and wouldn't happen under normal driving with varying rpms.

Any suggestions?

Old Scout · 09-29-2015, 10:16 AM

Might be off base here but believe our Alpines use an "exciter" system call "DU-vac" to control alternator charging. If not working or wired correctly, the problem with a bench test is that the alternator will "test" fine on the bench but doesnt address the on-board issues with the coach....

wolfe10 · 09-29-2015, 10:26 AM

Yup, three different "types" of alternator wiring-- and as Old Scout said, of not wired properly they will NOT work:

1. Standard alternator with just a B+ lug (may or may not have separate ground).

2. Alternator with external "sense" wire. Particularly common with diode-based isolator. Sense wire from chassis battery side of isolator or chassis battery itself to alternator. Small gauge wire. If left off, the alternator will NOT charge.

3. Alternator with 2 above and excite terminal that is only hot when the ignition is on. If not wired, alternator will not function.

Look carefully at the wiring diagram for BOTH your coach and you alternator.

Brett
2003 Alpine 38 FDDS

Terry W · 09-29-2015, 01:22 PM

Brett and OS,

I can see how the above conditions would/could result in a no charge situation. What I'm experiencing is an overvoltage on an intermittent basis. It will go from normal 13 - 14 volts to 15.8 - 16.3 for a short while and then back to normal. Can either of you think of an onboard problem that might cause this?

Like I said earlier, I feel that the last thing changed should be the first thing checked???

I am open to all suggestions.

Thanks

**pasdad1** · 09-29-2015, 01:27 PM

How are you reading the voltage while driving? Seems you need an independent gauge to verify readings with...In case the dash gauge is what is malfunctioning 😃

dennis45 · 09-29-2015, 01:27 PM

Quote:

Originally Posted by Terry W

Brett and OS,

I can see how the above conditions would/could result in a no charge situation. What I'm experiencing is an overvoltage on an intermittent basis. It will go from normal 13 - 14 volts to 15.8 - 16.3 for a short while and then back to normal. Can either of you think of an onboard problem that might cause this?

Like I said earlier, I feel that the last thing changed should be the first thing checked???

I am open to all suggestions.

Thanks

Terry,

Charge rate for the alternator is based on the voltage it sees from the battery. Before you remove the alternator, revisit all the connections on the back of it to ensure they are all clean and tight. A loose connection on the remote sensing terminal could fool the alternator into thinking the battery is dead.
Is this a new assembly or did you have it rebuilt?

wolfe10 · 09-29-2015, 03:48 PM

If this is an external sense alternator: Sure, a loose or corroded connection, particularly on the small gauge sense wire can cause that.

Were it me, and you have the alternator with external sense wire, I would run a new sense wire from chassis battery terminal of the battery isolator OR directly to the chassis battery positive terminal to the alternator. A couple of feet of wire and a few minutes time.

Brett
2003 Alpine 38FDDS

Terry W · 09-29-2015, 04:02 PM

I checked all the connections and they were all tight.

This is a rebuilt alt.

I would run a wire to batt. pos. but this is a problem that only showed up after an extended period of time at constant speed. When it did show up I could make it disappear by varying the rpms. I have the alt out and I will let the shop test it and run it as long as they feel is necessary. Hopefully something will show up. If not I'll see what they suggest as far as changing the internal electronics just for good measure.

I'll keep you all posted.

Thanks, Terry

Terry W · 10-02-2015, 08:08 AM

I posted before that I was having an intermittent overvoltage problem with the rebuilt alt. that I had installed a couple of weeks ago.

I pulled the alt. and took it to a local shop that I have dealt with over the years and have always had excellent results from. They bench tested and found some fluctuations in output. A teardown turned up a couple of bad looking connections and an overall poor rebuild job.

They replaced the stator, bearings and regulator and bench tested it. They say all is well and I have no reason to not trust them. They've been in business in town here for 37 yrs and are a father and son shop. They rely on word of mouth for business. It's one of those places that treat you like you're their best customer and your job is their most important job. Rare in So Cal these days.

Enough of the commercial, I will install the alt. this week end and move on to the next item on my list.

BTW, I contacted the installing shop and they requested a copy of the bill and said they will get a check on the way.

Thanks again for all of your suggestions!

Terry

dennis45 · 10-02-2015, 08:57 AM

Glad to hear things are coming together. When mine failed, I replaced it with a new OEM replacement for the very reason you are describing. Without replacing everything but the housing, all the components are subject to failure. Not to say a new one won't fail but the chances are much less. I hate doing things twice.