Positive Ground Question

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Positive Ground Question

Postby Woodee361 » Thu Sep 19, 2019 8:48 pm

Evening,
I've searched online quite a bit and haven't found a real clear answer to give me confidence. I even searched the forum and found a thread that Stan started that was called Brockway quiz 9. Mike Pacittos answer fits how my starter is wired almost. Mine has 2 battery cables and 2 smaller wires on the same stud of the solenoid. The other 2 battery cables are attached to the stud on the starter motor itself. It also has a strap that goes to the frame. The 2 smaller wires on the solenoid run from that stud up to another solenoid on the firewall. I've attached a couple of pics, hopefully they are clear enough. Does this sound like positive ground? I just don't want to cook anything when I try to get the engine to turn over.
Attachments
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Woodee361
 
Posts: 19
Joined: Sun Jan 06, 2019 11:28 pm
Location: Fort Valley Ga

Re: Positive Ground Question

Postby Huskiedrive2 » Fri Sep 20, 2019 6:53 am

Both positive and negative ground systems are wired similarly at the starter. Brockway uses a remote firewall mounted solenoid to trigger the big solenoid on the starter. This reduces the current draw passing through the ignition switch. A positive ground or negative ground system both have the wiring you described at the starter solenoid location. The only difference of course is which set of battery cables goes to the frame and which set goes to the solenoid.
Here are some ways to identify polarity of your electrical system - - -

Trace the two battery cables from the starter mounted solenoid out to the battery box(es). If you have a battery box on each side of the truck, one of these two cables will be drivers side, the other passenger side. Look at the size of the eye in the battery cable end. If it is the larger eye, that's the positive cable and it goes onto the positive terminal of the 12V battery (or the positive terminal of the two 6V batteries wired in series) In this example, since the positive cable is going to the starter solenoid, the negative battery cables will be attached to the connection at the starter motor. This terminal should also have a strap going over to the frame rail. This would be a NEGATIVE GROUND system.

Another way to identify positive ground systems on a Brockway would be to open the dash access panel and look at the outside circumference of the fuel gauge and/or the water temperature gauge (if electric). Usually printed on the side of the dash gauge will be POS GND if the system is wired for positive ground.

Your alternator may be a excellent source of information about positive or negative ground as well. If your truck has an external voltage regulator for the alternator, the regulator will usually be marked "for positive ground systems" if it is positive ground. If the alternator on your truck has an internal voltage regulator which can be identified by having only two large gauge wires going to the alternator, look near the output terminals for the + and - markings. If the + (positive) terminal cable is attached to the engine or mounting brackets etc., the truck is POSITIVE GROUND.

On a final note, if you cannot identify the system to a point you are comfortable with unhook the wires from the fuel gauge, water temperature gauge, and voltmeter (label and tape them) Unhook the alternator and external voltage regulator if present. Now you can safely start the truck regardless of polarity. The remaining electrical equipment is not polarity sensitive.

If you like, you are welcome to send me a private message through this forum and I'll give you my cell phone number. You can call and I'll try to answer any questions you may have.
Stan Augustine
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Re: Positive Ground Question

Postby Woodee361 » Fri Sep 20, 2019 8:48 pm

Thanks Stan, this is just what I was looking for!

So it appears that someone put new ends on two of the battery cables, maybe lol. There is a very slight difference in size with what I think is the smaller going to the solenoid. Still not a real definitive size difference to me.

Looked at the fuel and temp gauge but didn't see any markings saying positive ground. Fuel gauge is original I believe. Temp gauge is a Murphy with CCC on it, possibly from Crane Carrier?

The alternator has 3 studs on it with 2 wires hooked up. One wire is hooked to the Bat stud and goes back into the firewall, the other is connected to the engine block. I do think it has the internal voltage regulator. There is a plastic piece with 2 metal tabs that can be pulled out and rotated to determine voltage.

I might just go ahead and do like you said though and disconnect the specific components when I do see if it will crank. I appreciate the offer to pm you for your number. I actually tried to do that but it said the member was not accepting private messages. Maybe I did it wrong though.

Anyway, thank you for your response and great info. It helped me to have a direction to go and be able to eliminate some confusion. I appreciate your time!
Matt
Woodee361
 
Posts: 19
Joined: Sun Jan 06, 2019 11:28 pm
Location: Fort Valley Ga

Re: Positive Ground Question

Postby Huskiedrive2 » Sun Sep 22, 2019 2:52 pm

Matt - check your private messages, I sent you my cell number. Give me a call if you like. Stan
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Posts: 373
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Location: Horseheads NY

Re: Positive Ground Question

Postby Woodee361 » Mon Sep 23, 2019 6:27 am

Got your PM, thanks. I'll give a call this evening.
Woodee361
 
Posts: 19
Joined: Sun Jan 06, 2019 11:28 pm
Location: Fort Valley Ga


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