quote:

Originally posted by humbojb:
Hey, I've got tears in mine, too, because my Barth is still sitting in Tennessee, waiting for someone to put an new alternator on it to see if that solves my no start problem.

Huh? The alternator doesn't start your coach. I know you know that. Was it not charging while being driven? Did it just click?

I would hate to find out you got new batteries - alt - starter because someone is going to "install an alternator to see if it will start"

Red Flag! Very scarry.

There must be more to it then that! He should be able to jump you. He could then put a volt guage on the batteries and alternator and then "tell you" if it needs an alternator. Load test the batteries and take an amp reading while attempting to crank it. A test lite would go a long way here.


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1991 Barth Regal
460 EFI C6 Transmission
33' Oshkosh/John Deere Chassis

http://www.TruckRoadService.com/

"Without Trucks,

America Stops"

Bill, sorry to post such an abbreviated thing on the alternator. We had driven it over to Tennessee last October when our daughter lost her baby. It sat for a few weeks and when we went to start it, the chasis battery was dead. Our son-in-law, who is a pretty fair mechanic, spent a good bit of time checking things out and discovered the alternator wasn't putting out enough to charge anything. We actually started it with the aux start switch that put the house batteries in line. So we have a new alternator there. Of course the mystery is why the battery discharged in the first place. We had let it sit for far longer periods of time without that happening. We just had a Gear Vendors unit installed and maybe they wired it wrong and it's on all the time. But that wouldn't explain why the alternator went bad. Tere did start the generator once while the Barth was hooked up to shore power and the transfer switch in the "shore power" position. Any thoughts? We had no problems on the way over there last October. Both chasis and house batteries were working fine, and the voltmeters indicated they were both charging fine while the Barth was running.

This could be a combination of two issues, or just one, but either is centered about the alternator.

A bad diode in the alt would prevent adequate voltage to charge, and could likewise be leaking current to ground, discharging the battery. There could also be (very unusual) a short in the rotor, causing the same thing. Sometimes alternators do fail unexpectedly, and a diode is usually the culprit.

The chassis batteries could also be bad - and unfortunately, starting batteries have a low tolerance for being completely discharged, and this can be worsened by cold weather.

To emphasize what Bill said, both batteries and alternator should be load tested; many auto parts stores have benchtop alternator testers inside (The alternator has to be removed for bench-testing).

Sometimes a really messed-up battery (like one with an internal short) will cause a low voltage reading due to so much current being drawn, but this is thankfully rare.

Any good auto electrical shop can also make the tests, but you'd have to get the coach there. Hint: All the good auto electrical shops I've patronized look like disaster areas.

[This message has been edited by Rusty (edited January 26, 2006).]

quote:

Originally posted by Rusty:
Hint: All the good auto electrical shops I've patronized look like disaster areas.

That's the truth!

I would have you do a couple of things if you were standing there. I'll post this for others to see.

Shut off your coach & place a wrench to the pulley of the alternator with the batteries fully charged. If the wrench sucks in and gets magnetized then the regulator is full fielded and this is what killed your battery - replace the alternator

Start it up and see if your voltage is between 14.05 & 14.5 at the alternator then go to the batteries - there should be minimal drop between the two. If there is good voltage at the alternator and it is weaker at the battery check the wiring.

Check to see if your loosing voltage: you would disconnect the starting batteries ground cable only. Hook up a test light between the ground post and the ground cable. The test light should light if there is a voltage draw. Start disconnecting fuses one at a time until the test light goes off. Start at the memory wire fuses for anything that holds a clock setting - keep disconnecting until the light goes out. rehook all of the fuses starting from the first one until the light comes back on - keep hooking up fuses until all are in that won't light up your test light.

The fuses that are now out is where your voltage is going. Look again at what is on the circuit as a clock memory might cause the test light to come on but the mili-amps that it's drawing will light up the test light really dim. That type of draw is not an issue.

Only use a regular test light. A diode light is too sensitive and you can't tell by looking at one how strong the voltage draw is. Test the test equipment, make sure you have a good test light. If you hook it up and the test light does not come on then go inside and turn on any 12v light. The test light should go on - if it doesn't then you have something hooked up wrong between the ground cable and ground stud on the battery.

Good luck.

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1991 Barth Regal
460 EFI C6 Transmission
33' Oshkosh/John Deere Chassis

http://www.TruckRoadService.com/

"Without Trucks,

America Stops"

This falls into the "Duh" category, but I forgot to mention that it's a good idea to check the battery terminals for corrosion, then to clean them and spray with a good battery terminal spray (at least the positive terminals). If that's an issue, however, the alternator, if good, will not show low voltage....

And heed Bill's advice - sometimes (and the most fun) there are two faults that appear at about the same time - the alternator may be bad, but that may not be what's causing the unwanted discharge.

Electrical problems can be really "enchanting" - on my SOB, the voltmeter would suddenly show "blecchh". I checked the system and could find no faults. Took it to the local shop, and they discovered the terminal from the isolator to the chassis battery was bad, and that the 15A fuse to the voltmeter (among other things) had blown. New terminal, new fuse, and I'm on my way. But the voltmeter soon pegged at the low end.

So I pulled the second blown 15A fuse, and replaced it with the called-for 20A, and everything's been fine since...and found another circuit underfused, and a third overfused...

The most important concept to get from Bill's post is that there's no mystery to electrical problems - first, an issue (or issues) has to be isolated before a fix can be made. Unfortunately, a lot of "mechanics" are wary of "electricjuicity", and can't deal with the systematic search for the problem.

I'd suggest that if you have the time, you do what Bill recommends yourself, because there's nothing more comforting than knowing your motorhome's systems.

Yes Jim it is an MCI...and it would be more like calling a Barth....a Bounder. :>) Just read the posts in tech about diesel engins, ours is an 8V71 Detroit Diesel with an Allison 4 sp. auto trans. Wouldn't have bought it if it had still had a manual trans in it. Hey Dave thanks, you saved me from having to dig around looking for that photo...i forgot that i had sent that one to you too. Bill H must be there right now, i noticed he hasn't posted for a day or two. Still no rain here, getting close to 100 days with no rain.....i like it.

Jim i forgot to mention that there are 5 bus sites that i go to....2 are just MCI's the other 3 are all brands of buses and of course each of the other brands have their own web sites too. But of course this is my favorite site to go to. :>)