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Old 08-27-2013, 12:01 PM   #1
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Strange Electrical Issue

Hi, I'm new here so if I've posted this in the wrong forum, please forgive me.

I've got an '87 SouthWind. It's been a few years since I've used it. I finally got it to the point where most of the issues have been corrected. Yesterday I went to install a radio in the dash. I got my trusty digital VOM and started hunting for a 12 volt wire to power the radio.

This is where it gets strange... I couldn't find one. Most of the wires are showing -6 volts DC. I figured that my meter must have gone bad and went and pulled another meter out of my toolbox. It showed the same results. I even sampled the voltage off of the fuse block. I found a couple of wires that were +6 volts. I figured that the house batteries were old enough that they should be replaced anyway, so I bought a couple new batteries. That didn't correct the problem. When I disconnect the starting battery I don't get any voltage off of the fuse block.

By the way, all of the dash instruments appear to be opperating properly.

I'm really puzzled. Does anyone have any idea what is causing this?
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Old 08-27-2013, 01:33 PM   #2
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Are your new batteries 12 v or two 6 v batteries? Perhaps you have 6 v batteries wired in a parallel circuit instead of a series one.
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Old 08-27-2013, 01:34 PM   #3
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I would think the dash would primarily pull power from the starting battery. How many volts does it measure across the terminals?
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Old 08-27-2013, 06:08 PM   #4
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Yes the batteries are wired in parallel and they are 12 volt batteries. Each of the batteries measure 13 volts across the terminals.

"
I would think the dash would primarily pull power from the starting battery. How many volts does it measure across the terminals?"

I'm surprised also that the fuse block goes dead when I unhook the starting battery.

I'm stumped.
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Old 08-27-2013, 06:27 PM   #5
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Which fuse block are you measuring? There should be one under the dash or under the hood that comes from the chassis battery and supplies power to all the driving accessories, driving and head lights, heater fan, a/c, wipers, etc. Another fuse block is usually located nearer the house batteries or converter/charger and powers thermostat, refrigerator, water heater, interior lights, etc. All fuse blocks should read 12 v or actually 13.6 v or so. Since you installed new batteries, I assume the connections are clean and tight on the batteries, but how about the ground connection? Start there and continue to check voltage across ground and 12 v (+) until you find a bad connection. If you have shut off switches for house and chassis batteries, check voltage across the solenoids that turn power on and off. They could be dirty or corroded to the point they are causing resistance to current flow.
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Old 08-28-2013, 10:50 AM   #6
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So far everything I've measured forward of the firewall measures 12plus volts. I only goes to -6V on the passenger side of the firewall. I haven't been able to find the source that feeds the Chevy fuse block. The only thing that I can think of is that the polarity is reversed on the source that feeds the Chevy fuse block. But that still doesn't explain why it reads -6V instead of -12V.
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Old 08-28-2013, 11:31 AM   #7
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OK this is what I've done thus far. I've replaced the house batteries even though I knew that they weren't the issue. (They were old enough that I didn't want to rely on them.) Yes they are 12 volt batteries. Yes, they are wired in parallel. The voltage going to all of the fuse blocks installed by Fleetwood are measured at 12-13 volts. The battery isolator is wire correctly and show the correct voltages. The relays for the main and aux house show 12 volts. The starting battery is a few years old but is measured at 13.2 volts and has no problem starting the engine. When I plug into shore power the built in charger charges the house batteries. I haven't checked to see if it is charging the starting battery. I haven't pulled any DC lamps and measured the voltage, but when turned on they are the appropiate brightness. The diagrams that I recieved from Fleetwood show the house batteries in a different orentation than what is currently setup in the MotorHome. I understand that there was a recall due to battery cables rubbing against the oil cooler. This is probably how it was corrected.

When I get under the dash I get -6 volts instead of +12 volts. I have an electronics background and I know how to use a multimeter.

I posted because I was hoping that maybe someone has encountered this problem and has an answer.

I really appreciate your input.

Thanks

Steve
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Old 08-28-2013, 12:23 PM   #8
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The wires that show -6 v, are they wires to instrument lights or gauges? For a radio you'd want a full time 12 v source for the clock and presets, then a switched 12 v from the ignition. I guess I'd start at the ignition switch, and/or power to accessories. Lights are probably full time powered, wipers switched, etc. Sorry if previous suggestions were too simplistic, I always start with the most obvious.
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Old 08-28-2013, 09:05 PM   #9
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2 things come to mind.
1) The Chevy P30 chassis uses several fusible links. They are located at the starter and the junction block. They become soft and rubber feeling when failing and result in high resistance causing voltage loss to the P30 chassis loads.
2) I believe many fleetwood products use a Battery Control Center (BCC) under the hood. I think some of the chassis controls are routed through it. It is possible something in the BCC could be breaking down.

As far as the stock p30, alternator output is feed directly to the Headlight switch, Ignition switch, and fuses TAIL LPS and HORN. So, question becomes, do you see the full 12VDC at the TAIL LPS fuse when engine is running and only 6 VDC when ignition is OFF? If so, the you have a fusible link problem. A fusible link problem can make things look ok under the hood but have low voltage under the dash.

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Old 08-28-2013, 09:23 PM   #10
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Another issue that I've read about is the ignition switch or connector. So much is powered by the switch, it can cause heat to melt plastic. See this thread:
Ignition Switch
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Old 08-29-2013, 10:16 AM   #11
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Quote:
Originally Posted by Dave78Chief View Post
2 things come to mind.
1) The Chevy P30 chassis uses several fusible links. They are located at the starter and the junction block. They become soft and rubber feeling when failing and result in high resistance causing voltage loss to the P30 chassis loads.
2) I believe many fleetwood products use a Battery Control Center (BCC) under the hood. I think some of the chassis controls are routed through it. It is possible something in the BCC could be breaking down.

As far as the stock p30, alternator output is feed directly to the Headlight switch, Ignition switch, and fuses TAIL LPS and HORN. So, question becomes, do you see the full 12VDC at the TAIL LPS fuse when engine is running and only 6 VDC when ignition is OFF? If so, the you have a fusible link problem. A fusible link problem can make things look ok under the hood but have low voltage under the dash.

Dave

Thanks for the info.

I'll check the fusible links tonight when I get off work. By the way it's not 6 volts that I'm measuring. It's -6 volts. The dual battery isolator is showing 12 volts in and out for each of the banks of batteries. My biggest problem is tracing between the battery isolator and the Chevy fuse block. It has to be a point that is common to all of the circuts coming into the fuse block.

Also it doesn't matter if the engine is running or not. It reads the same.
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Old 08-29-2013, 10:17 AM   #12
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Originally Posted by BFlinn181 View Post
The wires that show -6 v, are they wires to instrument lights or gauges? For a radio you'd want a full time 12 v source for the clock and presets, then a switched 12 v from the ignition. I guess I'd start at the ignition switch, and/or power to accessories. Lights are probably full time powered, wipers switched, etc. Sorry if previous suggestions were too simplistic, I always start with the most obvious.
Every circuit on the Chevy fuse block is showing the -6v.
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Old 08-29-2013, 10:25 AM   #13
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Another issue that I've read about is the ignition switch or connector. So much is powered by the switch, it can cause heat to melt plastic. See this thread:
Ignition Switch
The one problem that has plagued me with this motor home is a starting issue. There are times when I turn the key to start and nothing happens. No clicking from the starter soleniod or any other sign of it attempting to start. If I continue to keep turning the key it will eventually decide to start. It doesn't matter if the engine is hot or cold. It will do it the first time I go to start it or sitting at the gas station after filling the tank. I've replaced the ignition switch, (No sign of damage to the wiring harness visable), replaced the starter soleniod, replaced the neutral safety switch. The Aux start button has no effect. I've even ran a wire directly from the battery to the starter solenoid. That hasn't cured the problelm. This has been the main reason why the motor home has gone unused for the past 4 years. I never know if I'll be stranded at some point.
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Old 08-29-2013, 10:42 AM   #14
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If you were using 6 volt batteries I could show you how you can get -6 volts.

Grab a 12 volt test light and see if the place you are measuring lights it up.

Plug an extension cord into one of the AC outlets in the rv and place the negative lead of your meter into the ground slot of the cord.

Probe the place you have been using for ground and then probe the place you are measuring -6 volts.

I suspect you do not have a good ground reference.
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