Isolator problem

86Scotty · 11-27-2012, 09:22 AM

In the Campfire section, you'll see that Twogone (Marc and Christine) dropped by for a visit on their way home from a trip. They stayed the night with me and then headed off this morning, only to return within about 30 minutes. Marc's van was having a strange electrical issue which I be someone here can shed some light on.
The van: late 90's Sportsmobile, 7.3 diesel, partially re-converted, but under hood wiring, isolators, solar, and coach batteries are unchanged from Sportsmobile's work.
The problem: rear solar meter and CO2/LP detector pinged at 17-18 volts when van is running. Normal operation when turned off. Also, front battery gauge (OEM dash gauge), which Marc says has always stayed right in the middle, was sagging pretty far to the left (low), yet batteries under hood showing a solid 14 +/- volts with van running.

My guess: Isolator problem. This van has the big blue heat-sink type beside one of the 2 van batteries under the hood. It isolates to the 2 rear coach batteries. We temporarily solved the problem by disconnecting the line to the rear batteries. Everything returned to normal except they aren't charging the rear anymore of course. Dash guage returned to normal.

Question is: Is there a way to test an isolator, or is there something else we should check?

Marc may want to add to or reword some of this when he gets home, but I wanted to go ahead and pick some of you guys' brains since this is probably a common setup and isolator on older Sportsmobiles.

Thanks!

Ford_6L_E350 · 11-27-2012, 11:21 AM

First, if the engine electrical system is at 14V, the isolator cannot make the camper system show 17-18V. I would suspect the solar charger is is running away (overcharging the house batteries). I'm not sure what the isolator does when the house voltage is greater than the starting battery voltage.

Of course, if that was happening the house side would continue to overcharge when the isolator was disconnected.

So, that makes me think about about a ground problem - probably on the house side, maybe at the isolator.

In any case, upgrading to a bi-directional separator is a good idea.

Mike

**daveb** · 11-27-2012, 11:40 AM

This issue wasn't related to high voltage but sheds a light on some of the problems the isolators had. It might help for what to look for.

viewtopic.php?f=14&t=3292

86Scotty · 11-27-2012, 09:41 PM

Marc, I had a brainstorm at work tonight. No problems until you popped your top and put it down the next morning. Perhaps there is a dead short caused by a kink in your solar wiring (the only wiring that runs through your PH fabric). I wish I would've thought of that before you left so we could raise/lower the top a couple of times and see if your solar stopped freakin' out!

Give it a try!

Eric

**daveb** · 11-28-2012, 08:07 AM

Being the panels put out 17-18 vollts I'd be looking at the controller. Check the input and output voltages. If you throw a blanket over the panel(s) does the voltage drop? [Edit] If a ground is compromised from the solar panel it might try to find it from the chassis. I really don't know what that would do.

twogone · 11-28-2012, 08:13 AM

Most of this issue makes no sense to me, as I have no mechanical/electrical skills. I gotta get the van in to Ray's shop by about Monday and between him and you guys, I believe we can find the "rat".

As to this thread, I want to tell everyone that Eric (86Scotty) was totally a hero for making the effort and taking the time to save Christine and I from what was a dead-in-the-water situation. He had tools, patience (with the babbling idiot standing beside him), and deductive skills that had us able to roll, in minutes, from a total shutdown and 8 hours from home... on the third straight day of 500+ miles. Not sure how to pay that back properly, but I'll figure something out

@86Scotty

86Scotty · 11-28-2012, 08:49 AM

Quote:

Originally Posted by daveb

Being the panels put out 17-18 volts I'd be looking at the controller. Check the input and output voltages. If you throw a blanket over the panel(s) does the voltage drop?

Dave, the panels never put out high voltage. The voltage spike was only when the van was running, and the voltage would jump from 17ish to 18ish when I revved it up. this was only on the rear batteries measured at the solar panel battery guage and also with a digital (cig plug) battery guage I had plugged in right beside it at a power point. The front (van) batteries never spiked when running, revving or not. Definitely related to alternator charging here I think. The only link to the solar panels, I think, is that his solar controller is also his rear battery guage, so this is where we were 'seeing' the spike. At 18 volts it was making his lp/co2 meter start to chirp and flash, but somehow Marc said his Engle fridge is unaffected by the situation. Still clueless and thinking it might have something to do with solar panel wiring through the PH top, but I'm no solar expert, it just seems like the likely culprit since the van rolled in to my driveway fine, he popped the top, lowered it the next morning, and as soon as he fired up to leave the problem arose. Marc never even plugged in at my house.

@Marc, no problem. 1 cold beer on the proper occasion will be plenty.

Well, OK, make it 2, or 3. How much time do I have?

**daveb** · 11-28-2012, 09:24 AM

As long as you got off Marc. I'd have someone check voltage coming into the isolator and the output of the isolator. Isolators generally allow charge in one direction only and that's from the alternator to the house system. They are not like separators that can push a charge in two directions. Seems to me if the voltage regulator is bad you would see variable voltage at the vehicle dash gauge and the chassis battery. On both the regulator and isolator you might have to apply a load to cause the oddball voltage to appear. Never heard of an isolator adding voltage to a system. Usually they fail to allow current through so I'm with Eric, seems like a regulator issue. I've had alternator regulators intermittently work and fail.

Good luck.

Scalf77 · 11-29-2012, 04:14 PM

Instructions for testing a isolator,
INSTRUCTIONS FOR TESTING A SURE POWER ISOLATOR WITH OHMMETER*:
1. Remove all wires from the isolator.
2. Using a needle movement ohmmeter RX-1 scale or a digital ohmmeter diode scale, hold the Red* probe on the terminal "A" and with
the Black* probe touch terminal #1 and #2, and the "E" terminal for 3A isolators (group 2), and the "R" terminal for (group 3) isolators.
A good isolator will show a current flow from "A" to #1, #2 and "R", and no current flow to "E".
3. Next, hold the Black* probe on the "A" and with the Red* probe touch terminal #1 and #2 (terminal "E" and "R", if used). A good
isolator will allow no current flow from "A" to #1, #2 or "R" and will show current flow from "E" to "A".
4. Hold one probe on the aluminum heat sink, being sure there is contact by scratching through the protective coating. Then touch
with the other probe, terminals "A", #1, #2 (the "E" terminal for 3A isolators [group 2] , the "R" terminal for group 3 isolators). A
good isolator will show no current flow.
5. Colored terminal indicates "E" post on group 2 isolators and "R" terminal on most group 3 isolators.
*On some import ohmmeters, the red and black probes are reversed for these tests.
**If using a digital ohmmeter, a diode scale MUST be used.

You also may have a circuit breaker between #2 and house battery that has gone south. If you are using the E terminal it is also probably fused.

-greg

twogone · 01-27-2013, 08:05 AM

OK, alright, all fixed-up! Ray convened all of his resources and input from this thread. All evidence pointed toward the isolator as the fail point. He swept-the-hall on this project. We got new isolator (replaced 17 yr old) and new starting batts (replaced 4 yr old), and a new (not rebuilt) OEM alternator. All systems normal!

One of Ray's advisors is a 48-yr veteran mechanic who specializes in automotive electrical issues. He warned that the failed isolator allowing everything the alternator could produce causes "spiking" in the alternator and PROBABLE damage in the alternator/regulator, some of which is not readily detectable, so he advised NEW, OEM-only in this fix to be confident that all is well. I had just put the rebuilt alternator in last Spring, but not willing to risk another issue for our upcoming trip.

Moral to the story... if your house system goes full-on crazy, suspect the isolator!

HUGE Thanks to 86Scotty for his help in all this

and, my curiosity grows... what does Scalf77 do for a living?