Electrical Issues

mrdibbles · Unread post by **mrdibbles** » December 1st, 2007, 2:53 pm

Hey Guys-
Prior to installing the new harness I could leave my Mutt sitting for 2 weeks, without starting, and she'd fire right up. Now with the new harness, front and back, if I let it sit for a week the batteries are dead. No start. Not so much as a half hearted crank.

Anyway I thought the issue was a bad ground. Maybe combined with a bad turn signal box on the firewall. When I replaced the box the turn signals started working right and I thought my problems were over.

Sadly I just realized I am not done with this. She sat for a week and she's deader than hell.

I am out there now charging the system via jumpers but I have a problem. What do you guys think it may be? I am an idoit with electricity. However this idiot did plug everything in right because all systems are a go except for the batteries going out.
Regards,
Matt-

Ralph Fuller · Unread post by **Ralph Fuller** » December 1st, 2007, 7:49 pm

When you disconnect the negative (-) post on the battery do you see a spark indicating something is on.

mrdibbles · Unread post by **mrdibbles** » December 1st, 2007, 8:08 pm

Hey Ralph-
I think the answer to that is yes. I removed the battery cable from the battery closest to the passenger door, the cable to the front, and it does spark.
Matt-

Ralph Fuller · Unread post by **Ralph Fuller** » December 2nd, 2007, 9:26 am

Matt:
I used a test light and started at the "On/Off Switch". This is the kind of test light that has one wire that you alligator clip to a ground, stick the point through the covering on the wire so the point touches the wire inside.
My short turned out to be a bare wire inside the original, factory wrapping. I found it in the dash behind the steering wheel. It was feeding constant juice to my distributor, and running my battery down. Wire #27 on the switch was the constant feed.
TM 9-2320-218-20 has a wiring diagram. If you don't have the TM (Technical Manual) click here and go to page 2-86:
http://www.pedros.cz/M151/TM_9-2320-218-20.pdf

Unread post by **rickf** » December 3rd, 2007, 10:30 am

Matt, I have an easier method but you will have to wait until lunchtime, My break is over/

Must be nice to work at home

Rick

Unread post by **rickf** » December 3rd, 2007, 1:28 pm

Matt, Give me a call.
Rick

Joe · Unread post by **Joe** » December 6th, 2007, 9:13 am

Matt,
As the Pennsylvania Dutch would say, "you've got a short circle"!!! Dead batteries are no fun so it might be time to think about installing a battery lockout switch on your jeep after you find the battery drain problem. I put a switch on my A2 just for security sake and I like it.

Joe

Spike · Unread post by **Spike** » December 6th, 2007, 12:08 pm

I did the same thing Joe. I installed mine with the key part through the battery box and the terminal end between the batteries. The housing is black and with the key removed I don't think the bad guys could easily figure it out. And, it isolates the batteries. I have been known to leave the light switch in the wrong position and have killed my batteries more than once, this protects me from a *senior moment*. Still you need to find the short. The two areas that I've had electrical problems with have been the flasher/turn signal switch and the horn wire. That and the capacitor.

Floyd · Unread post by **Floyd** » December 6th, 2007, 1:17 pm

Ralph: Can you insure you have a good harness before you install it. If you have continuaty with all wires is it OK? I win this one Matt when it comes to any thing electric, the brain goes dead.

Floyd

mrdibbles · Unread post by **mrdibbles** » December 7th, 2007, 10:06 am

Hey Guys-
I'd like to install a battery cutoff switch. I have one on my Healey and I like it. That way I can sleep well knowing she's "OFF" and that it'll sit without draining. Plus I like the idea of a mild theft deterent.

Again though I am little stupid when it comes to Volts and Amps so if anyone can "make this easy" for me I'd appreciate it. Where should I mount the switch and how does it connect to the harness (or batteries)? Does the swtich need to be a 24v switch and if so where can I get one?
Thanks!
Matt-

raymond · Unread post by **raymond** » December 7th, 2007, 11:17 am

Mr.D

You can use a 12 volt switch. About any battery cutoff switch should work. The amperage rating should be okay on any quality one. There are 2 ratings, one is the continuous, and the other is surge. The continuous rating should be more than the total draw of all accessories running simultaneously which on a M151 is not that much, probably less than 20 amps. The surge rating is for starting. Also remember that Ohm's law says that if you double the voltage, you halve the amperage. Because these things operate at 24 volts, they draw less than half the aperage they would if 12 volts. Most of the one's Ive seen will handle at least 200 amps continuous and 500 surge. The general consensus is to put it on the ground. That way it still cuts off the power if you hook anything up 12 volts. Where you put it is up to you, but seeing your beautiful restoration, I would make sure it is out of sight. A good place might be to mount it in the battery box, with the key or switch handle sticking through the wall into the tool storage area. It's not real convenient, but not very noticeable either. I mounted mine originally between the batteries sticking out the front where the passengers feet are, but the switch got broke off. I put a new one in and put it in a hole that was already on the dash on the passenger side. My M151 is a cut model and is a mix of A1 and A2 and Army and USMC parts, so I wasn't too worried about correctness.

Spike · Unread post by **Spike** » December 7th, 2007, 11:40 am

http://www.jcwhitney.com/autoparts/Prod ... 26/c-10101

This is the switch I used. The one with the red key.

I drilled an appropriate sized hole between the battery compartment and the tool storage area, approximately between the two batteries. The terminals point towards the batteries. I then drilled two smaller holes to fasten the switch to the compartment divider. The red key is removable. So to energize the system I lift the passenger seat, raise the tool compartment lid, insert the red key, give it a quarter turn and it locks into position and the current flows. Disconnected, I think, it would be hard for a scoundrel to figure it out, additionally if you locked the seat down with a pad lock that would make it very difficult to bypass the terminal if the bad guy is mechanically inclined. There are a few different ways to stuff your batteries into the battery compartment. If the batteries are installed like these the upper left hand captioned terminal goes to the engine compartment; this is the one you want to isolate. Once it is disconnected it should be long enough to stretch to the isolation switch. You'll need to purchase or fabricate a wire cable of the same gauge that goes from that baterry post to the other isolation switch terminal.

I have the artistic skills of an arthritic chimpanzee

You can interrupt the power at any of these cables, positive or negative. This is how I did it.

mrdibbles · Unread post by **mrdibbles** » December 7th, 2007, 11:51 am

Thanks for the help guys. I went ahead and purchased that one your recommended Spike. I like that's it has a removeable key.

Floyd · Unread post by **Floyd** » December 8th, 2007, 1:38 pm

Soooo! I guess their is no real way to tell if a harness is bad prior to installation?

Floyd

Unread post by **rickf** » December 8th, 2007, 6:20 pm

Floyd, The answer is yes and no. Checking for opens in the harness is easy, Just put one lead of an ohm meter on one end and the other lead on the other end of a wire. No reading means an open circuit. Wires shorted together is another story, The combinations of wire to check for continuity acroo circiuts is astronomical! A circuit tracer would work. clip the generator on one wire and check to make sure the signal does not cross to another wire. Come to think of it you could do that with a battery, put power on one wire and check all of the others to see if you have power anywhere else. I know electrical inside and out, it was one of my specialities along with carburetors but I can not explain it.

I can show you but not explain it in any way that makes sense. That is why I was never a teacher.
Rick