Alternator issues

[oldtech]

I have a 96 Monaco with a problem I've seen many others with. A flaky Tach with inconsistent voltage. I've installed new brushes and replaced a bad diode and it seemed ok but on a recent trip it raised it's ugly head again. It currently has a Hehr Powerline 190 alternator. I've seen others have replaced their alternator with the Delco Remy 28SI 200 amp. If anyone has done this I'd like to hear about it!

First what did you do about the battery isolator, replace it, with what?
The 28SI has a single sense circuit how do you keep from overcharging the second set of batteries?

I don't know what the pulse signal is on the DR but I'm sure it's not the same as the Powerline, is there an adjustment on the tach for the different pulse output?

Any ideas would be appreciated.

[wa8yxm]

Is the isolator a diode type or a relay type? (Solenoid)

In either case the single sense line is all you need, here is why.

Let us assume the house batteires are low but the chassis battery is near full. In that case the house batteries will get ALL the charging current, don't matter if it's a diode or solenoid type since they have the lower voltage they get it all (Assuming the connections are good and the wire is heavy enough)

Reverse that and the chassis battery would get it all

Once they have both reached the same state of charge.. Then they finish charging at exactly the same state of charge rate.. That is if they team up at say 80 percent, they will each reach 81, 82, 83.....99-100 percent at exactly the same instant.

I might add,, all those things you have heard about "Do not connect different size batteries in parallel" When someone starts yammering about that plug your ears,, You do just that EVERY TIME you start your coach.

[oldtech]

Diode type.

Yeah I kind of figured that would happen but I've read so many articles discussing methods to charge house batteries, and I was a little concerned about overcharging. Relay, Smart isolators, dc-dc chargers all have benefits and sound like a better idea... but I think you're right a single sense should be sufficient regardless of the isolator. But I'll still have to make a decision of the isolator, it's a 190 and I'm going to 200 although that might not matter.

I have read something about Delco Remy's not working with diode type of isolators but I can't find that article again. Any knowledge? I know there's some voltage loss in the diodes. Any recommendations of a isolator replacement? Is it true most new MH have relay type of isolators?

My other puzzle is the tach. Has anyone pulled out the tach on a Monaco and know if it has any adjustments for pulse signal?

I appreciate any help.

[Mike Canter]

Oldtech, my recomendation is to take your Hehr alternator into a local alternator/starter repair shop and get it tested and rebuilt by experts. Don't complcate matters by swapping out to a Delco. I have this local alternator repair shop in Marietta, Georgia that has been repairing my starters and alternators for 20 years and have never had one fail again. He uses the original parts and is great. You can find a shop like that around you. Call a truck repair place and see who they use.

[oldtech]

The alternator was repaired by someone recommended by a Cummins store locally. It was an old guy that's been doing them for 100 years, he took one look at it and said, ' another old piece of junk.'

I had read many others similar stories as mine, many discussions of Delco 28SI, and that's what he said too. He told me he could get my Hehr going and did, ( he put in the brushes and diode), but said it should be replaced. I should add, he wasn't in the business of selling them.

The Delco is a fraction of the cost and is a newer, more efficient design. The Hehr has only 39,000 miles on it. Not good.

I'm going on a long trip in July and I'm not interested in heading out with a questionable alternator. Besides I like to tinker and this looks like a good opportunity.