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RufussSewell · 02-14-2014, 02:49 AM

Ok. I have two problems with electrical shorts.

1. My transmission ECU panel is turning on/off/on/off and the relay is clicking. I can't get into gear or drive at all. Also the PacBrake is firing over and over at the same time that the ECU restarts.

2. Power from my generator flickers about once per minute. On shore power I'm fine.

I have a volt meter and plenty of time. I've watched several videos but they seem to skip important steps. Like what do I set the dial on the volt meter to? Should I have the key off or power on or engine running? Am I looking for full 12VDC?

I'm sure there is just a loose connection or a bad relay or solenoid. But I need the "electrical shorts for dummies" guide to find it.

Are there any good tutorials or YouTube videos out there?

Libero · 02-14-2014, 03:23 AM

It does indeed seem to me that you have an intermittant DC problem in your chassis system. It may or may not be a short circuit. It could be just a bad connection, this could be on the hot or ground side.

I would recommend first to determine if all DC electrical connections are clean and solid. Any short circuit would likely get hot and blow a fuse unless it was an intermittant battery short or anything before a fuse. There is no fuse to blow if the problem is in a battery, but a faulty battery might blow up with an internal battery short. (I had an internal short in a car battery once, it was intermittant at first and eventually the battery blew up, what a mess that was with sulpheric acid all over the place. I neutralized with baking soda but batteries can be dangerous so if you have a face shield it is always a good idea to wear it when messing with a battery.)

Just loose connections could also get hot if they are on high current circuits and that is a potential for fire. So inspect every plug and wire connection you can see for tightness, including the battery posts. Sometimes they get loose inside the battery.

If you want to measure DC Voltage, put you meter to the DC scale and set for an appropriate voltage range, (if it has a range setting) Since you will be measuring 12-15Vdc, select that range that is ABOVE but closest to 15Vdc. For example it might be a 30v range. It depends on the meter. And polarity matters also. Black on ground and red on hot for most meter leads.

I would first do a connection and battery inspection with the ignition off.

Then measure the voltage. You should measure about 12.5V. Having done that, start the engine and measure the voltage again. It should be higher. It might go up to 15V but it should be higher than 12.5V. The RPM and the state of your charging system will dictate the voltage with the engine running.

Your reference to all is fine when on shore power is not quite understood. Do you mean you the vehicle runs and you can put it in gear with shore power connected???

I don't believe house batteries are in this equation re the transmission and PAC brake ets

Good luck - hope I was helpfull.

RufussSewell · 02-14-2014, 04:14 AM

Hi, thank you!

I just mean that problem #2 (gen power flickers once per minute or so) doesn't happen on shore power. Just when the gen is running.

Libero · 02-14-2014, 04:25 AM

Quote:

Originally Posted by RufussSewell

Hi, thank you!

I just mean that problem #2 (gen power flickers once per minute or so) doesn't happen on shore power. Just when the gen is running.

Thanks. I suspect that is a different issue but you might check all connections from the GEN. Just wondering about the transfer switch also. It comes into play here. One side is shore power and the other side is from the Gen but again loose connections are often the culpit. With all AC power off, (shore plug disconnected and gen Off) check all your AC connections from the Gen including the ones at the transfer switch and if you can see/feel the transfer switch/relay contacts, inspect them also. Take a screwdriver and turn any screw connections slightly left and then secure with a good right turn.

Good luck.

RufussSewell · 02-14-2014, 05:18 AM

Ok, I'll check the screws.

I'm really just trying to learn the basics so in the future I can fix things myself. I know that when I put the red pin from the volt meter on the pos post of the battery and the black pin on the neg post the meter reads 12.xx. In various locations I can touch the pins onto two cables and it'll read 12v.

When I'm looking for a problem I want to check at the source (battery) and at the problem area (trans ECU) and then follow from each direction until I find the problem.

I'm not sure if the power should be on while I'm doing this. Or the engine on. Or everything off.

If everything is off won't it lack power because it's turned off?

Also perhaps I should just buy new batteries. The thought of them exploding is pretty scary.

Libero · 02-14-2014, 07:24 AM

I suggest you check the connections and voltage with the ignition off first. Then start the engine and check voltages again with the engine running. This is just a test to see how your charging system is working. Then you could turn the engine off and put the ignition on and continue checking voltages to troubleshoot. There might be a fuse to your transmission. Check all fuses also while you are doing that check. But the clattering relay certainly points to a bad connection or a possible short somewhere but a short should normally pop a fuse if it is in a protected circuit. Anything from the battery to the fusebox, or an inline fuse is not protected.
I do not want to scare you about checking the battery, but they can be dangerous under certain circumstances. Go ahead. Check the voltage and make certain the connections are secure.

You have not yet determined if the battery(s) are the problem so I would do further checking in that regard.

Good luck.

RufussSewell · 02-14-2014, 12:57 PM

It's being towed to the shop :(

I'll update what the issue was.

deandec · 02-14-2014, 01:38 PM

You might have the shop focus on restoring the transmission function rather than finding and fixing a potential short in the wiring.

If they can bypass the coach wiring effectively, that would allow you to use the rig while trouble shooting the remaining electrical issues.

Isolating a wiring short in the wiring maze could get to be expensive....

bsinmich · 02-14-2014, 04:20 PM

A Short is when the wires contact each other and provide a Short Circuit before getting to the proper accessory or light. An open circuit is when the connection is broken by a break in a wire, a loose connection, open fuse, or anything else that interrupts the flow of electricity. Open circuits are probably more common than shorts.