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Old 02-07-2012, 01:18 PM   #1
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Battery Isolator: What is wrong with this picture?

OK, so I have this big old beast of a class B, and while she runs great, her battery isolator either is not working, or is wired wrong, or may be just plain shot. If so, this is causing two problems. One, my batteries keep equalizing, and of course that means that I won't have enough power for the engine battery to start the vehicle. Two, because of this switch that I can't seem to identify, I can't seem to get her into the right position to keep the batteries independent of each other. Here is what I have:

Photo #1 is the iso itself. The top center post is the "A" post which apparently is supposed to go to the alternator. The left-lower is battery 1 (engine) and the lower-right is battery 2 (house). The leads from post "A" and post #1 come off the iso and go across the engine compartment together. All good, so far.



Photo #2 is the engine battery. It looks a little fuzzy, but what we have is both the "A" lead and the #1 lead hooked into the pos (+) terminal of the battery. This can't be right, can it?



There is a relay bolted to the fender-well, right next to the iso itself. It appears to be a standard automotive type. The lead from post #2 leads into this relay and then, I believe, the relay goes to this switch, located underneath my steering column.



Obviously there are no markings on this ancient little switch. All I know is that it is a three-position switch and the photo currently shows the switch in the middle position.

I assume that all three positions signify something, although what is a mystery to me. I'm thinking that one is for charging both batteries, and another might be a way to use battery #2 (house) as a booster to battery #1 (engine). Beats me though, since I seem to detect no changes in the way the batteries charge or discharge based on which position the switch is in. It may be the switch is bad or even the relay, but who knows, since I really have no idea which switch position does what, and no real way of finding out.

Getting back to the wiring for the iso, I am having problems getting battery #2 to charge when driving. It seems to take forever, and I don't mean a few hours. I am talking about a full day's worth non-stop driving, or even more, to get the house battery up to snuff. That can't be right. That battery is relatively new (1 year old) and does not have any problems charging when I put her on a standard trickle charger.

I suspect that the "A" lead being wired into the #1 battery (+) terminal is the reason shes charging so slowly. I want to move that lead to the back of the alternator.

Is that correct, or will wiring directly to the alternator output post possibly blow my #2 battery, alternator, or both? I don't think it would, but if anyone knows for sure, I'm all ears.

Anyway, this is all on an old Ford Intervec Falcon. I know that Falcons aren't all that rare, so maybe there is another Falcon owner lurking around here that has the same setup and can fill me in on the wiring as well as the switch.

I hope all this is not too confusing, and thank you in advance for any help or ideas you may have.

One more thing: Is there any way to test the isolator itself to see if it is in proper working order? I have all the basic tools I need (multi-meter, automotive tools, wire and fittings, etc.) but I just don't have the know-how.

Edit: OK, obviously I am having problems uploading the photos. I am using tiny pic, which is what I normally use for forum posting. Is there a preferred pic re-sizer for this forum?

Edit #2: Fixed

Edit #3: For clarity, he says, with a straight face.
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Old 02-07-2012, 03:20 PM   #2
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Equalizing merely means that high voltage is being applied - nothing special in the isolator or elsewhere. Equalization voltage is typically around 16dcv - is that what you are measuring at the batteries? If so, the voltage regulation in your alternator is bad and it is either (1) not getting the voltage feedback it needs to regulate or (2) the regulation circuit in the alternator is bad.

What is the measured voltage at house and engine batteries when the engine is running? Have you removed and cleaned all connections?

At a guess, I would thing the switch selects the house power source, one battery, the other, or both. That would not affect charging - it appears the charging voltage comes straight from the isolator terminals, not that relay you mentioned. What else is wired to that relay?
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Old 02-07-2012, 03:38 PM   #3
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The alt is punching out 14.4 and it's only the months old, so it's strong. There is a much larger drop at the house battery though, only a little over 13. Thats why I want to connect the "A" lead right to the alt output post.

As far as the relay goes, it apparently leads to that switch. I'm sure that there is another line that splits off it to the
house battery, but I don't have visual confirmation of that.

My main concern tough is why is the house battery drawing down the engine battery? If I use the house power for very long, my engine battery goes dead and I need to jump start the vehicle. Isn't the iso supposed to keep that from happening?
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Old 02-07-2012, 04:44 PM   #4
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I'm not sure how old your rig is but have seen pictures of that type of isolater. Mine is a 01 and the isolator on it is quite different. The one on mine looks more like a solenoid with 4 terminals, There are 2 larger terminals, 1 is hooked to house side and the other to chassis side. The other 2 wires, one being a ground and the other goes back up to the alternator. If the isolator fails then as far as I understand the house batteries can draw down the chassis batteries. On the back of my alternator there are the 2 big terminals pos. and neg. and also 3 smaller terminals. One wire there is to the ignition. and the other goes down to the isolator. There has to be power to both those terminals when the ignition is turned on. Yours may be a different system so I don't know if this will be of help. To me it looks like your may be wired wrong. Good luck.
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Old 02-07-2012, 08:34 PM   #5
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That sounds like a mess.

That's a circuit breaker next to the isolator. Normally, that wire would lead to the house/aux battery.

It sounds to me like you need to trace some wires. Compare what you see to what's supposed to be there. The 2 wires at the engine battery are not right.

When we were installing these, we used to run the "A" and #1 wires to the back of the alternator. "A" would go to the alternator itself, and #1 to the wire that USED to go to the alternator.

The isolator can be tested with the engine running and the wires removed from #1 and #2. You should have power to all 3 terminals. You should also have power at the #1 and #2 wires - without being connected to the isolator.

The switch under the dash is a separate deal. Don't confuse it with the first one. They are not related.

Hope this helps!
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Old 02-07-2012, 08:47 PM   #6
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Actually it helps a lot. Confirms what I thought about the placement if the "A" lead.

I am not sure what you meant about the #1 l lead though. If it replaces the lead from the output post of the alternator to the #1 battery, won't I lose my connection from the alt to the batt? Maybe just reading it wrong.

And if that switch isn't for the iso, that actually makes more sense. But WTH would it be for? Doesn't seen to affect anything on the vehicle when I play around with it.

I now feel reasonably certain that the isolator is shot though. I'm definitely going to check it with the multi first thing in the morning. Thank You very much.
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Old 02-08-2012, 08:51 AM   #7
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Originally Posted by straygoose View Post
Actually it helps a lot. Confirms what I thought about the placement if the "A" lead.

I am not sure what you meant about the #1 l lead though. If it replaces the lead from the output post of the alternator to the #1 battery, won't I lose my connection from the alt to the batt? Maybe just reading it wrong.

And if that switch isn't for the iso, that actually makes more sense. But WTH would it be for? Doesn't seen to affect anything on the vehicle when I play around with it.

I now feel reasonably certain that the isolator is shot though. I'm definitely going to check it with the multi first thing in the morning. Thank You very much.
#1 lead attaches to the wire that's been removed from the alternator.

So to follow the power from the alternator - first to the "A" terminal on the isolator, through the diode inside the isolator, to the #1 isolator terminal, then to the original wire hooked to the alternator - which will supply power to the chassis systems exactly as it did when originally connected directly to the alternator.

Maybe try thinking of it this way? If we could mount that isolator in back of the alternator, we could cut the wire on the alternator and just insert this isolator between the cut wires. The wire from the alternator would lead to the "A" and the other side would lead to the #1. The isolator should be completely transparent to the chassis systems?
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Old 02-08-2012, 02:42 PM   #8
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First thing I would do is contact the manufacturer of the isolater and get a wiring diagram for your particular model.
Then use that information to trace and confirm if your wiring is set up correctly. Otherwise you are only guessing, and that can lead to problems.
Good Luck
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Old 02-08-2012, 04:00 PM   #9
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Quote:
Originally Posted by ahicks

#1 lead attaches to the wire that's been removed from the alternator.

So to follow the power from the alternator - first to the "A" terminal on the isolator, through the diode inside the isolator, to the #1 isolator terminal, then to the original wire hooked to the alternator - which will supply power to the chassis systems exactly as it did when originally connected directly to the alternator.

Maybe try thinking of it this way? If we could mount that isolator in back of the alternator, we could cut the wire on the alternator and just insert this isolator between the cut wires. The wire from the alternator would lead to the "A" and the other side would lead to the #1. The isolator should be completely transparent to the chassis systems?
Ok, got that, but that means a re-wire job is in order. The leads being used right now on the iso are probably 12 ga and I'm going to need at least 8 ga, if not 6 ga. Otherwise, the alt will just fry all.

Looks like I'm off in search of some auto grade wiring. No way am I going to trust this flimsy stuff the previous owner rigged up.
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Old 02-08-2012, 08:38 PM   #10
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Straygoose.......I'm still confused by what I'm reading from others. The isolator is definitely wired wrong. Those type of isolators were prevalent in the old days.

If you DID NOT have the isolator and the vehicle was wired in a non RV configuration, the alternator wire would run to the battery of the vehicle for charging. Since the purpose of the isolator is to charge two battery banks, it splits the charge. I believe those older models were simplistic and chose the battery bank with the lowest charge and charged that bank, eventually moving to the other bank.

In you're configuration, the alternator lead should go to the center post with a substanstial cable, probably a 6 or 8. Remember, this is not a starting cable, just a charging line. The #1 post should go to the engine battery and #2 to the house battery(s). Keep in mind that those isolators were also notorious for failing. I would rewire the iso;ator and then test to see if it's working by checking to see if you're getting a charge voltage of 13.8 - 14.5 at both #1 and #2. With the engine off, you should get 12+ volts at both #1 and #2, but not at "A".

I'm not sure what your last photo is, but my guess would be an early version of an emergency start/jump switch.
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Old 02-08-2012, 09:01 PM   #11
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That's my main concern right now. It's hard to tell in the photos, but those two red leads for the "A" and #1 posts look like 10awg, or maybe even 12awg. I got my hands on the Sure Power spec sheet for the isolator, and it recommends 8awg for any run under 15' (with circuit breaker in-line). I have to run from the alt lead across the engine compartment to the "A" post then from the #1 back to the alt lead. It measures out to probably 10' total, so I'm going to go with the 8awg and add a breaker between the alternator and the isolator, per the specs. I am considering over-engineering it with 6awg, but I'm not sure it will be necessary. After that, I will deal with the wiring for the #2 side of the circuit. I figure I might as well lay fresh wire down on that side too, since it looks like 10awg also. Just need to figure out how it threads its way through the chassis back to underneath the sofa.

Can't check the operational status of the isolator itself until I get the wiring straight, but I still believe it's bad anyway, due to the fact that the house side of the system pulls down the capacity of the engine side, if that makes sense. If the store has one in stock I'll probably just go ahead and renew without even checking.
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Old 02-08-2012, 10:30 PM   #12
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straygoose.....An ohm meter from the #1 post to the #2 post should answer your question if the unit is good. There should be no continuity.
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Old 02-09-2012, 09:29 AM   #13
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straygoose.....An ohm meter from the #1 post to the #2 post should answer your question if the unit is good. There should be no continuity.
That doesn't test it for the most common failure mode - an open diode. You would want to test for continuity from the "A" terminal to the number one terminal, then the same to the #2. This thing is just a couple of heavy diodes installed from the "A" to #1 and "A" to #2. Because you are checking a diode, in the case where it's showing open, reverse your meter leads and try it the other way. Not going to get into why this is, but as long as it works one way or the other you're good to go.

Personally, I wouldn't replace this with another. I'd go with a relay. I'd just go with a common relay that looks like a starter relay, but rated for constant duty - commonly seen for powering snow plow hydraulic pumps. MUCH simpler operation/installation, maybe less money, and just as reliable (maybe more?).
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Old 02-09-2012, 04:13 PM   #14
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Let me gather up all my new info and I'll get back to y'all. I just re-wired to get rid of those two wires on the + post. Ohmmeter tests indicate that the isolator is shot, but I want to do it again in the morning to make sure. Thanks for your patience and your help.
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