My chassis batteries (2ea 12 V starting batteries)) had discharged to arund 6 volts and would therefore not start my 1993 38 ft Regency. I pushed the aux. start switch and attempted to start. There was definitely more power but it would not start. All I got was that the engine would crank in short spurts and would not start. The coach batteries (4 ea 12V deep cycle) were fully charged. I had previously been able to start my MH with the aux start switch.
My question is, can the isolation switch go bad (i.e. burned contacts, etc.)?
Any suggestions would be appreciated.

It is possible that the severely discharged starting batteries were sucking too much from the coach batteries to leave enough to start the engine.

I would say that your isolation switch was doing its job, as evidenced by the "more power" you observed.

Now, as to the paralleling relay, it was at least partially working, again, by the "more power" you noticed. Whether it was passing full current or not, it would take a meter to tell for sure.

I would replace or recharge the start batteries and see what happens. I suspect they are goners, having been run down so far.

Any idea why they went down?

I can't figure out why the battery drain. I measured the drain and it was only 50 miliamps, all due to the voltage meter in the dash. I think I will move the lead for that meter over to a switch breaker instead. The coach had only sat idle for no more than 3 weeks since last use. I had this happen before and had the batteries checked by the shop and they checked okay. These batteries were purchased last November. A friend at work who used to drive semis told me that the Interstate batteries can be troublesome, especially in determining why they drain too fast.

Other than that I am at a loss.

I also wonder if another relay in the chassis battery circuit just before the isolation relay could function to cut out the chassis battery during the "jumping" operation. Any suggestions?

I thought I had a phantom load on my house batts too. The batteries are 2 years old but never really got used after they were installed. The previous owner left the coach plugged in and ran the batts dry. After I bought the coach I filled the batts up with distilled and charged them up. They held a charge no problem and I drove the coach home, 2000 miles.

After sitting for a week unplugged, the batts dropped to 8 volts. I had the dom switch turned off and thought I had a phantom load killing the bank. I charged the batts back up and took the cables off. Guess what, dead batts in a week.

It wasn't a phantom at all, just abused batteries that will need replacing. These will become my franken-batts and will do some experiments on them. Going to do a test with some EDTA and my desulfator.

I think to keep it simple I would put a disconect on the chassie battery. you could see if your bat. drain goes away or bad battery and seperate for aux start. simple and not an project.

Here is the chassis schematic as sent to me by Spartan. I am currently redrawing it to make it easier to read. When done I will make a copy and revise to reflect how my coach wiring interfaces with the spartan chassis wiring.


The V.I.M. and Allison harness to the ECU are shown on the right hand side of the schematic about half way up just under the horizontal line.

quote:

Originally posted by Lance Walton:
Here is the chassis schematic... I am currently redrawing it to make it easier to read. When done I will make a copy and revise to reflect how my coach wiring interfaces with the spartan chassis wiring.

Lance sent us a cleaned up PDF of this drawing for our files. You can zoom in and see the circuits a lot better on this PDF. When he draws the Spartan-Barth wiring diagram I'll link this too.

SPARTAN_SCHEM_ORIG.pdf (105 KB) Spartan Chassis Wiring - 1993

quote:

Originally posted by Bones:
will do some experiments on them. Going to do a test with some EDTA and my desulfator.

I would be very interested in how that goes. My work with EDTA was before I had a charger with a desulfator feature, so I don't have much to compare. I just used one or the other.

Do you have the Home Power Magazine article on EDTA? I used to buy mine from some off-grid or survivalist supply company. "Trail Supply" or something like that. I believe it is in the article.