TheSamba.com :: View topic - Need help from electrical gurus

Sun Feb 28, 2010 4:43 pm

On my 1974 Westy, there is something that is killing batteries. I have gone through two new ones this year. Where do I start to trace the problem? I have an electrical tester, but I am not proficient at using it. I know how to test voltage, but that is about it. Any help would be appreciated. Please be as specific as possible with your answers since electrical is my weakness.

Sun Feb 28, 2010 4:49 pm

what exactly is happening to your battery?

Sun Feb 28, 2010 4:52 pm

Remove the negative post from your battery and connect your meter between it and the cable, set it to mA if it's not showing anything. Then start removing fuses and either run back or have someone watch the meter to see if the draw stops.

Sun Feb 28, 2010 4:54 pm

It dies overnight. I know my alternator is charging properly b/c I can restart the bus after a drive. If the bus sits overnight, there is nothing left on the battery in the morning. It will drain so low, that my charger won't even charge it. I have to jump it to get enough juice (min. 3V) to get my charger to work.

Sun Feb 28, 2010 5:13 pm

Do what BusDaddy is recommending and check for errant current loses. First set the meter to the scale you need to test for 12VDC. I don't think you have a milliamp size leak, probably something much bigger.

You should check that you are getting the correct voltage while it is running as well. If it is only barely charging, that would amplify the effects of any current leaks.

Sun Feb 28, 2010 5:21 pm

check that the cigar lighter isn't pushed in.

Sun Feb 28, 2010 6:55 pm

do you have an aftermarket stereo/amp installed? these are the usual culprits. But follow busdaddy's advice, even though he's got a picture of Cindy in his avatar.

Sun Feb 28, 2010 8:17 pm

regis101 wrote: check that the cigar lighter isn't pushed in.

Regis, you know me better than that.

Sun Feb 28, 2010 8:30 pm

panicalum - I am off Friday afternoon unless the stay in the court furlough case isn't lifted. Bring it over then or during the weekend and we'll help you solve it. It is probably something like a stereo or amplifier being left on. It can also be a gauge left on (excluding CHT) I've seen overhead lights left on too. We are off Old Auburn Road near Antelope so you aren't too far.

Another thing that can kill it is corrosion. If any of the ground straps or battery cables are corroded that can lower the voltage available to the battery to charge it. If you start off with a partially charged battery and never get it up to a full charge that can cause issues too. You should have about 14.5 V between Battery POSTS when it has been charging for 5 or 6 minutes.

FYI - if you start out with the mA setting on your meter and the current is too high you will fry your meter or pop the minature fuse in it. If you do it start with the 10A setting first. Another way of testing it is let it sit 10 minutes after driving it to disapate any hydrogen then pull one of the battery cables. If it sparks when you hook it back up then something is on drawing current.

Sun Feb 28, 2010 8:45 pm

panicalum wrote: regis101 wrote: check that the cigar lighter isn't pushed in.

Regis, you know me better than that.

Yuk, yuk

Mon Mar 01, 2010 1:40 am

SGKent wrote: panicalum - If it sparks when you hook it back up then something is on drawing current.

A famous cause of discharge in these Type 4 buses, after you pulled every single fuse and still get a spark between the negative terminal and post, is the alternator diode bridge assembly. One of those stupid diodes will start leaking to ground even though the alternator can still charge the battery. A common parallel symptom is ghostly light dimming/brightening around idle at night.
Colin

Mon Mar 01, 2010 1:49 pm

Here's a story to relate to you guys. I was working in North Carolina as an Airline mechanic for US Air back in the 90's. One of our inspectors who was an excellant mechanic was having a problem with his diesel passat. The battery would drain after a couple days and it was killing him. He was out in the parking lot during work trying to solve the mystery and was convinced that he had some kind of bad computer causing the draw. He tried everything and had been working the problem for several days. Then he pulls out the rear seat back and could now see into the trunk. Low and behold the damn trunk light was on. Always look for the simple things first.

Tue Mar 23, 2010 6:58 am

Alright, I finally got back to working on the bus. Here is what I have found. By turning the key, I no longer get any power to any part of the bus. I disconnected the power cables from the battery terminal (except the large cable that goes to the starter) and started looking for problems. With the black multimeter wire going on ground and the red one on the wire that goes to the alternator, I am getting a voltage of around 5V. that should be reading 0, right? Also, I was getting no power at the fuse box. I found that if I disconnected the large red wire that supplies power from the battery to the fusebox, there was 12.5V of power. This led me to believe that I had a problem at the fusebox or "after" it.

After disconnecting different wires at the fusebox, I found that there was a problem with the emergency flasher switch. By disconnecting the red power that supplies the switch, power returns to the fusebox. Either the switch is bad, or there is a live wire grounding out. Is this correct? How do I tell if it is a bad switch? Be very specific since I don't understand resistance and other electrical properties.

Even with that switch disconnected, I am not getting anything by turning the key. That could mean that my ignition switch is bad too I think. There is power at the wire connection into the ignition switch. I took the ignition switch out and found that the plastic wire connection looks "cracked." There is a little black pin (or end of a wire) that doesn't look like it is sitting in the plastic housing properly.

What are my next steps for testing. I really need to get this thing back on the road. Thanks in advance for your help.

Aaron

Tue Mar 23, 2010 7:13 am

Replace the ignition switch

Tue Mar 23, 2010 7:24 am

Doesn't the ign switch get its power via the flasher? I would borrow a switch from someone before I replaced anything.

Tue Mar 23, 2010 7:25 am

What about the flasher switch? I guess that it could also be the headlight switch since those are connected.

Tue Mar 23, 2010 7:47 am

You should still have power to the fuse box whenever the large wire going to the starter is hooked up. The fuse box originally got its power from the starter. All the other wires that may be hooked to the positive post on the battery have been added at some point.

The power should run, first to the starter, then to the fuse box, then an unfused circuit should run to the ignition switch. The ignition switch then sends unfused power back to the fuse box and to the coil and FI relay in the rear of the bus.

Tue Mar 23, 2010 7:52 am

Sounds like you need a wiring diagram. Spend some time and trace everything out learning the flow. I've never seen power loss from a bad flasher or headlight switch but I sure have seen one many times from a bad ignition switch.

Thu Apr 08, 2010 7:42 am

So, I found that my stereo was grounding out and causing some electrical draw. I have disconnected that. I replaced the battery + and - cables. Also, I replaced the flasher switch, the key tumbler, and the ignition switch but there are two extra wires: Brown with blue line and solid gray. I think they are for the buzzer and dome light. I now have power at the fuse box and at all of the connections, but still get nothing when I turn the key. Without any wires connected, I get a click from the ignition module when I turn the key. That indicates that it is working correctly, right? No electrical is working even though there is power at all the switches. What's next? Steve, please come help me. The Ranch Run is this weekend. I really want to take my bus.

Thanks again for the help.

p.s. I lost that tiny little screw that holds the ignition switch in. I lost it after I tested and got nothing. When I took it out again, It disappeared. Does anyone have an extra?

Thu Apr 08, 2010 8:11 am

"I lost that tiny little screw that holds the ignition switch in. I lost it after I tested and got nothing. When I took it out again, It disappeared. Does anyone have an extra?"

it's just a very small metric thread like a 3mm or something. I'm sure you can find a screw that will work.