Charging issue while driving
 

On our maiden trip with the rf18 I noticed that the house batteries were not being charged while driving (the house volts will slowly drop on both the dash and inverter panel), although it seems like the chassis batteries were fine. I thought maybe the isolator was bad so I used the aux switch to combine them. That doesn’t seem to help. Starting the generator and running it while driving kept the batteries charged. I just tested the isolator and it checks out okay. The aux switch and combiner solenoid are functioning properly also. I figured it was since you have to engage it when parked to keep the chassis batteries charged and that works correctly. So I am leaning towards an alternator issue. The dash gauge always reads 13.5 roughly with no fluctuations. Do you think that it is just not putting out enough current to keep up? Is there something else in the system to check? Thanks.

I find that when I am driving down the road and using the inverter that my voltage is around 13.5 to 13.9 routinely. That has been what it has been since I put the Samsung in and that has been 3 years. I thought it was fine and never questioned it. By the way, that is not the dash gauge readings, which can't give you that precise of a reading. I get those readings from a digital gauge I have plugged in and have used since the fridge change.

I pulled the alternator out. It spins freely. I was thinking maybe the belt could be slipping. It only has OTR on a tag no other model numbers. The only connections to it are ground, positive and a two conductor plug. The r and I terminals are not hooked to anything. Does anyone know what model this might be so I can look up more info?

What is the alternator putting out ?
Check th voltage at the alternator and the isolator .

Ours charged over 14 driving down the road with the inverter running our household refrigerator .

Here are some pics of it. I was guessing it was a Leece Neville, but the back doesn’t look like it.
https://www.wanderlodgeownersgroup.c...ictureid=10029
https://www.wanderlodgeownersgroup.c...ictureid=10030

It looks like a delco 21si so far. That is a 100 amp unit if so

I they came, according to owners manual, with 160 amp.

I don’t have a charging circuit schematic, does any else? The wiring has been all hacked up. Four splices within 6 inches of the alternator. There are three wires in the loom. One labeled “tach” is chopped off. One labeled “ign to reg” goes to pin 1 of connector. One labeled “alt output” (I think) goes to pin two of the connector. I assume that the “ign to reg” comes from the key switch? Is the “alt output” the sense wire? What is the tach wire for?

Leroy, here is a condensed version along with cruise control info from WOG files section. https://www.wanderlodgeownersgroup.c...leShooting.pdf

That is a Chicom knockoff of a 22SI, so it's probably 160 amps if it still works.

I found an old post from ac7880 about his alternator and it seems mine is wired the same way. “Alt output” wire sees 12v from the chassis bats. “Ign to reg” wire sees 12v when key is in run position. I checked at the alternator, bus off 12.94 volts, bus on voltage jumping wildly from about 13.2 to 14.2. Reving the engine same result. From there I checked at the isolator.

Bus on: chassis 13.9, alt 14.2, coach 13.6
Bus off: chassis 13.5, alt 13.5, coach 13.1

Plugged in/aux off: chassis 13.3, alt 13.3, coach 14.6
Plugged in/aux on: chassis 13.7, alt 13.7, coach 13.7

I’m thinking a new alternator is in order especially if it’s a Chinese knockoff.

What kind of isolators do you have? It could be fragged alternator doing that, but it could be a screwed up wire, too. Isolators don't often go bad, but it can happen.

The isolator is a sure power 1602 160 amp model. The alternator has the j180 short mount. It looks like the original would have been a long mount from reading other posts. Does anyone with a long mount alternator know your belt number? I figure I’ll put it back to the correct mount size. It was a bear getting the belt off now and it definitely won’t work with a long mount.

I have two spare belts in the basement a gates k080610 and a Cummins 3911572. They seem to be the same length. I didn’t pull the one from the engine to compare sizes and it doesn’t have any markings left. The Cummins belt says it was made in 2000 so likely was for the original alternator. Crazy it has been riding around in there for 19 years.

K080610 is the correct belt for my 1994 BMC. Your alternator looks similar to the Delco unit that was on our BMC when we bought it. I bought a new Leece Neville DUVAC alternator, installed it and put the Delco in the bay for a spare.

As originally equipped(at least for 1994), the large Alt+ terminal that runs to the center post of the isolator should not show voltage when the engine isn't running. I've read on irv2.com about guys replacing alternators with a "will fit" and then finding goofy electrical issues such as things being energized when they should not be. Wouldn't your engine not shut off once upon a time? That and the hot Alt+ terminal make me think you've got other issues besides just Alt output.

Here is a basic DUVAC troubleshooting chart that may be helpful:

https://www.dixie-electric.com/tsb/TSB_704.pdf

I will confirm the path of the alt + wiring to the isolator and let you know where it goes.

It is true, for a while my engine did not like to stop playing. That stopped after I replaced all of the batteries and replaced the cabling in there.

Sounds logical. I’ll report back on what is in the path of the alt to isolator circuit tonight.

Thanks.

Okay guys I need the think tank to activate. I checked just installed the new 28si 160 amp alternator. I checked on what Dave said above about the isolator center post not having 12v when the engine is off. The wire from the alternator to the isolator center post seems to be a uninterrupted run and now doesn’t have 12v when the engine is off. I guess there was a problem internal to the old alternator. I thought it was fixed. However when you start the engine you get a solid 3v output regardless of rpm. I then removed the sense wire and ran it to see if maybe it just doesn’t output if the bats are full, solid 3v. Next I watched a delco video that shows that the sense circuit compares the bat voltage on the output to the bat voltage on the sense input to regulate output. I thought maybe the issue was the isolator in circuit so I moved the chassis bat wire from its isolator post to the alternator post to tie the alternator directly to the battery. Shebang the alternator is putting out a solid 14.3 at idle. So here is the question. Is my isolator bad (it seemed to test fine) or is the alternator not compatible with a isolator system? Obviously I can’t leave the connection as is or the coach bats could draw down the chassis bats. Thoughts?

Isolator could be bad, they are just big diodes. The alternator doesn't care about the isolator and there will not be any compatibility issues between them.

Honestly I would toss the isolator(s) in the garbage and run an Eaton Surepower 1315-200 in its place. The diode isolators will drop any voltage going through them 0.7 volts on top of whatever loss you have in your wiring, but the Surepower doesn't because it's a giant solenoid with some smarts built in. The reason they run the sense wire from the alternator down to the isolator is to have the regulator make up the voltage drop while charging.

Found the issue, now I have to come up with a solution. The 28si requires bat voltage on the output initially to start the exciter. So it you bridge on of the battery terminals to the alternator post briefly it will take off as intended. I guess they make isolators with an excite terminal for this. I’ll compare the cost of that to installing a circuit that brings power to the post briefly at startup. Has anyone else gone down this road?

LeRoy - don't do all that monkey business. All a 28si needs is a power wire on its output directly to a battery (or isolator if you still use them) and a ground strap. It will not discharge the battery by being connected like this.

The problem is there is not 12v on the isolator terminal until the alternator begins producing power.

https://www.waytekwire.com/images/it...or_80003_f.png

Throw the stupid diode isolators out and do it the right way... Sorry to be so blunt :)

https://www.rvupgradestore.com/v/vsp..._Isolators.pdf

Might be of some help , page 3 .

Switching to the solenoid type Andy is talking about is a great way to go . You don't have the voltage drop from the diodes .

A hot wire on a correctly working alternator should not have much current draw when not running .

Just got back from dinner and read the sheet on the 1315-200. Looks like I could tie the chassis bat and alt out to the main terminal and the aux bat to the other terminal. It sounds like it will tie the banks together when either one reaches 13.2 volts. If that is the case then I wouldn’t have to use the aux switch to keep the chassis batteries charged when on shore power. It sounds like a win on both fronts. Is this what your using in your bus Andy?

Got one on order. Thanks for showing that to me Andy.

I do use it on mine and it works perfectly!

I installed this a while ago, but have been busy since. BMC people might like to know that this eliminates the need to combine your batteries when parked. I didn’t use the combiner function in the 1315-200, instead I retained the original system. This also solves the issue on having bat + visible to the alternator output if you switch to a 28si alternator. Thanks for the recommendation Andy. Both battery banks were rock solid today during a cruise around town.