Isolater Question - This is a rough one

[KurtFranz]

2002 Chevy Roadtrek 190 - Had an issue with my house battery not charging while driving. Investigated and found out that the isolater was bypassed. The isolater is a surefire 12023A similar to the original that came on the van.

The PO had the alternator replaced a few days before I picked up the van.

Here we go....

The isolater adapter cable still had the red sense wire connected to the chassis terminal on the isolater - no biggie there it is not doing anything. Also the yellow wire that goes to the ignition was still connected to the isolater - no biggie

Here is where it gets odd and deviates from the instructions and everything I have researched up to now. The alternator cable and the chassis battery cable were connected - screwed together and taped up. No biggie that makes sense if one is bypassing the system. However, there is a black wire that came from the same wire loom as the yellow wire and it is clamped onto the end of the chassis battery cable. Not certain where this black wire is coming from but it was routed with the yellow wire inside of the spiral wrap loom. Nowhere have I seen any mention of this with regards to setting up the isolater. So that is the first place that I am looking for some insight. So the alternator cable, the chassis battery cable, and the small black wire are all screwed together and taped up. I am fairly certain that whatever that small black wire is there would be no issue whether or not it is screwed together as it is now or connected to the isolater - it is getting power either way. I did not want to tear into the wire loom and tear that all apart at this time to find out exactly what is is - if there is no reason to do that.

The second issue - and the one that I am more concerned with - is the adapter cable that goes on the alternator where the factory cable was. The factory cable plugs into the adapter cable on one end and the other end goes into the alternator. If you are familiar with an isolater install you should know what I mean. The question I have here is that the adapter plug that goes into the alternator has 4 wires coming out of it - three plus the red sense wire which is the purpose for this. However, the factory cable only has 2 wires coming out of it - two in the middle two holes. I am wondering if the third wire coming out of the adapter plug which goes into the alternator will cause any electrical issues - it dead ends in the connection where the factory plug with the 2 wires is connected.

I had everything hooked up according to the books, tested the voltage across the terminals with the engine off - good results. Tested the ohms - good results. But when it came to starting the engine and checking - i chickened out because I was worried about the possibility of the two anomalies discussed above causing damage to my alternator or ignition system or something.

If anyone makes it to this point in the post and has not thrown up on themselves, I would be interested in your insight. Past experience has prompted me to post this before I move any further ahead.

[mloganusda]

Here is a photo of my 2017 Winnebago Trend wiring. I know it is not the same but is labeled with wire names. This may help with your wiring to trace how it should be hooked up.

[markopolo]

Originally Posted by KurtFranz

...................... However, there is a black wire that came from the same wire loom as the yellow wire and it is clamped onto the end of the chassis battery cable. Not certain where this black wire is coming from but it was routed with the yellow wire inside of the spiral wrap loom. Nowhere have I seen any mention of this with regards to setting up the isolater. So that is the first place that I am looking for some insight. So the alternator cable, the chassis battery cable, and the small black wire are all screwed together and taped up. I am fairly certain that whatever that small black wire is there would be no issue whether or not it is screwed together as it is now or connected to the isolater - it is getting power either way. I did not want to tear into the wire loom and tear that all apart at this time to find out exactly what is is - if there is no reason to do that. ......................

Can't help you with that small wire. It's a good idea to try to find out what it's for though. Does it have a fuse on it?

Originally Posted by KurtFranz

..................The question I have here is that the adapter plug that goes into the alternator has 4 wires coming out of it - three plus the red sense wire which is the purpose for this. However, the factory cable only has 2 wires coming out of it - two in the middle two holes. I am wondering if the third wire coming out of the adapter plug which goes into the alternator will cause any electrical issues - it dead ends in the connection where the factory plug with the 2 wires is connected.

As far as I know the OEM setup just used the two center wires. Adding an isolator necessitates the use of the added sense wire to eliminate the voltage drop. As that last wire (P for pulse/phase, I think) would be dead ended I'd assume it's OK to just tape it up and add shrink wrap or a zip tie to make sure the tape can't come off.


You should end up with 5 wires on the 4 post isolator. Excite, sense + chassis bat, alternator, & aux bat.

[KurtFranz]

Originally Posted by markopolo

You should end up with 5 wires on the 4 post isolator. Excite, sense + chassis bat, alternator, & aux bat.

Yep - that is exactly what I have except for that black wire. I doubt that anything catastrophic is going to happen if I test it due to the fact that it is clamped on the Chassis battery cable and was getting power previously when bypassed.

[JohnnyFry]

At this point, since someone, apparently the alternator installer, has modded the system, probably because they did not understand the whole isolator thing.

My approach would be to disconnect the mysterious black wire and tape it up, for now, and reconnect the isolator: Alternator wire to the center terminal and batteries to the 2 side terminals. I would fire it up and measure the voltage at each of the isolator terminals. You would be looking for 13+ volts at each of the battery terminals and roughly 0.75 volts higher at the center terminal. If this is OK, I would use a clamp on DC ammeter to measure the current at each of these leads. If the alternator fails to come up and produce voltage I would connect the black mystery wire to the engine battery side of the isolator, but in series with a 12 volt light bulb in order to limit current. If this turns out to be the exciting lead the alternator should start to produce voltage. Negative results will call for more sleuthing.

[KurtFranz]

How long does it take for two 12 volt batteries to "equalize" if the isolater is not functioning correctly and one of the batteries is dead?

For example, if I hook up my isolater, it is bad, and the house battery is currently dead, how long would it take for the chassis battery to become "equal" in voltage to the house battery resulting in both batteries being dead? This is assuming that both circuit breakers are good.

Is this something that happens rapidly or over an extended period of time?

Or is it a "it depends" kind of thing?

[KurtFranz]

FWIW -
Hooked it all up left the black mystery wire in place. Ran the fan and lights continuously until house the battery went dead. Let it sit for a day and the van started fine. Had 9 volts on the house battery and 12.4 on the chassis battery - not 12.7 - House battery is charging when engine is running. Alternator is putting out 15 at the isolater when running and 14 plus on both batteries. Also the dash volt gauge is reading a tad over 14 when running - it was reading 12-13 prior to this. I do not believe the 2002 express van had the alternator that fluctuated based on the electrical demand as so many people mention.

After I get my intake manifold gasket replaced I am going to perform additional testing to see if the chassis battery gets to 12.7 and stays there. Maybe this will help someone else out who runs into this problem.