Inter battery connector sparking

[totaljoint]

Question for the electrically inclined:

I've had problems starting the 712 for a couple of months. In the process of tracking down cause, the batteries (2year old Interstate) I found the dash voltmeter was reading 18 or less volts last week. I jumped started it just fine using the instrucionts re-posted recently here. Assuming the recent cold weather was the culprit, time to change/charge the batteries right?

As I was unscrewing the connectors on the short wire between the batteries (to take them out to replace/charge), there was sparking under the connector screw as I turned it. Not between the two posts, just when I loosened the connector screw on one post.
My main electrical switch was off.

The batteries behaved well holding charge until 2 months ago. No new connecitons were made. Invertor/Webasto all off and down line from main switch anyway.

Shouldn't there be no current between the batteries with that main switch off, and therefore no sparking when loosening the connector between the batteries? Does this indicate an occult drain explalining the recent low voltage on the batteries? Sneakng up in the last two months, could this indicate a corrosion/short on the hot side causing the drain?
Thanks for your thoughts!
Ed

[Jimm391730]

Shouldn't there be no current between the batteries with that main switch off, and therefore no sparking when loosening the connector between the batteries? Does this indicate an occult drain explalining the recent low voltage on the batteries? Sneakng up in the last two months, could this indicate a corrosion/short on the hot side causing the drain?

Yup, you are correct. Somehow, some where, you have a drain that continues to pull current even with the battery key off. There is a relay that parallels the key, the relay is supposed to close when the engine is running (in case the battery key is turned off at that time, the electrical system needs the battery(s) connected to operate properly when the alternator is running). I believe the relay is behind the spash plate just in front of the battery box (I think, I've never looked for it) along with the switch. Check there first; it is possible that the relay has welded the contacts closed or some other type of falure.

24 volts is enough to create some sparking if current is flowing and then interupted. No current should be flowing with the switch off, so obviously the switch and/or relay is not preventing current flow as they should.

I suspect that your phantom drain is small, perhaps just a few tens of milliamps that eventually discharge the batteries in a few days/weeks. You can remove the jumper between the two batteries and replace it with a multimeter set to DC current and you should be able to measure some current flow; the current should be zero when things are correct and as you figure out what is going on with the battery key or relay you should see the meter show zero current when the issue is corrected. Don't turn the ignition key on, or any other loads in the truck while the meter is substituted for the jumper or you might fry your meter or blow it's fuse if it has one.

Best of luck,

Jim M.

[edzz]

Disconnecting the jumper when the truck is stored also will eliminate the chance of parasitic drain. Is also a good theft deterrent.

Bypass relay test - http://www.sdp-pinzgauer.org/html/bypass_relay.html
Good source of battery and battery charging information - http://batterytender.com/resources/technical-info
Ed

[David Dunn]

With the main switch turned off, there should not be any parasitic drain at all. As Jim suggest, the relay could have failed in a close position, if ANY other electrical item has leads going back to the batteries, it will defeat the main switch .... and possibly making that electrical component a fuseible link if you attempt to start the truck while the switch is off

[pcolette]

The battery switch relay is located in the engine compartment under the driver's seat. Not the easiest spot to get to but not impossible. I removed 2 of the heat duct hoses and replaced it from underneath. Be sure to mark your wire locations because the wire colors are dirty and often inconsistent from the wiring diagram.

Here's a photo from underneath:


Relay part number: 7111850380

Paul

[totaljoint]

Thanks for the info.
Update: I disconnected the batteries, charged them individually and when I hooked them back up, no sparking, no mysterious current between batteries with all systems off. Starts up really easy (just like when I first got her from Jim) even in the cold and damp. Go figure.
I tried to find the relay. Can't fit my head between the cylinder heads and body from above, and too many hoses from underneath for me to deal with at this temp. Wonder if the access panel just to the driver's side of the tranny cover will get me to this?
Jurgen's site descibes a test by finding the Molex connector....what's that? This will be a job for a warmer day.
As a definitive electrical shut off, has anyone installed a switch between batteries? Considering something like this:
http://www.harborfreight.com/heavy-duty ... ag=froogle
Ed

[edzz]

Jurgen's site descibes a test by finding the Molex connector....what's that? This will be a job for a warmer day.
As a definitive electrical shut off, has anyone installed a switch between batteries? Considering something like this:
http://www.harborfreight.com/heavy-duty ... ag=froogle
Ed

Molex is a manufacturer of connectors. The Pinzgauer has numerous “Molex” connectors in a variety of locations and sizes.

http://www.molex.com/molex/index.jsp?langPref=english

In general saying “Molex connector” is kind of like saying look in the parking lot for a ford vehicle, it could be a car, truck or a front end loader etc.

As far as the cut off switch it could be a good idea, would also provide an additional level of theft prevention as long as the battery box is kept locked. I have however found some of the Harbor freight electrical products to a bit questionable.

Ed

[Jimm391730]

Jurgen's site descibes a test by finding the Molex connector....what's that?

THE Molex connector is the one that feeds power to and from the alternator -- it is located at the bottom edge of the air tin on the passenger side, roughly beteen the front carb and the distributor. These connections are subject to corrosion and when they fail (not if they fail) it is likely that you will lose a voltage regulator or alternator (ask me how I know!). Check them at least every year or so. They tend to corrode to nothing between the crimp on the wire and the actual spade connection, this is where the plastic housing can hide problems.

Jim M.

[undysworld]

Re. the Harbor Freight switch: I got a switch from a BMW mechanic buddy. (BMW ships them with a battery disconnect switch, and the dealers remove and return them to the factory.) It appeared to be the exact same switch that Harbor Freight sells. FWIW. (I use it in my Jeep)

Jim,
Thanks for a reminder. Just a thought. Is it the Molex connector that is crappy? Or just age on the crimped connections? Just wondering if it would be an improvement to replace it with a Weatherpak version? I know the Molex fits very nicely in it's mount, but perhaps a weatherproof connector and newly crimped wires would solve issues? Or am I just redesigning a wheel?

Paul

[totaljoint]

perhaps a weatherproof connector and newly crimped wires would solve issues?

Or spray it with CorrosionX?

[David Dunn]

Two of the earliest problem points for gas pinzes in "civies" hands were the corroded battery cable in the molex connector ( big red wire) and bad/ disconnected idle solenoids.

Certain phrases and words became synonymous in Pinz vocabulary (ex... red death = flaking of the liner in the gas tank... (people make too much of this), molex connector = the connector through the tin on the engine ( though other connectors, this is the most frequent to have a major problem).

Other than a little more " security" and "peace of mind", there is no reason to add another point of failure to the truck... You already have the same type switch behind the seat. If you do find you have a power draw with the switch off, find the problem and fix it... don't mask it..

[David Dunn]

perhaps a weatherproof connector and newly crimped wires would solve issues?

Or spray it with CorrosionX?

Do a search, there are many, many threads fixes for the connector... don't overthink it... the original connector usually survived 25 plus years

[Jimm391730]

Well, because of the location of "THE" Molex connector it does seem to fail more often on these trucks than other connectors. One failure mode is to lose the power from the alternator, which causes the regulator to over power the alternator rotor, either frying the rotor (in my case) or ruining the regulator. Some trucks have had no problems, some have. Some have repaired/replaced the Molex, some have used other connectors, some have hard wired through the shroud directly to the alternator. But it has been mentioned many times that it is worthwhile to examine this specific connector for deterioration as failure can be costly.

How it is maintained, fixed, or changed to prevent failure is less important than ignoring it and allowing a failure to happen, but you must be certain that whatever is done is as dependable or more dependable than the factory Molex. A little maintainence goes a long way in ensuring the Molex works as expected for a long time.

Happy Holidays to all,

Jim Mettler