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rogerdodger · 05-09-2013, 02:47 PM

This is where a voltmeter or test light is used. You need to find which wire has the voltage applied to it from the brake controller. Whether red or black, because the other wire should be connected to the frame ground somewhere near the front A-frame. Then you connect one wire from the breakaway switch to the "Hot" brake wire, and the other breakaway switch to the +12 volts at the tongue jack. This will apply full +12 volts from your trailer battery to the brakes in event of a trailer/tow vehicle separation while towing. Assuming, of course, that the breakaway cable is connected to the tow vehicle.

jerryc41 · 05-09-2013, 02:58 PM

Quote:

Originally Posted by rogerdodger

This is where a voltmeter or test light is used. You need to find which wire has the voltage applied to it from the brake controller. Whether red or black, because the other wire should be connected to the frame ground somewhere near the front A-frame. Then you connect one wire from the breakaway switch to the "Hot" brake wire, and the other breakaway switch to the +12 volts at the tongue jack. This will apply full +12 volts from your trailer battery to the brakes in event of a trailer/tow vehicle separation while towing. Assuming, of course, that the breakaway cable is connected to the tow vehicle.

How can I do that without a tow vehicle? The wires at the wheels are black and gray.

rogerdodger · 05-09-2013, 03:14 PM

It will be difficult, unless you have a very good test meter, then you may be able to test using an Ohmmeter. The wire with resistance is the "hot" wire, the one with 1 ohm will be ground. However, if any of the connections are poor, then you will get about the same readngs, because the brake coils are low resistance. Best to wait until you can hook up to your tow vehicle, test for the presence of voltage.

jerryc41 · 05-10-2013, 05:00 AM

Quote:

Originally Posted by rogerdodger

It will be difficult, unless you have a very good test meter, then you may be able to test using an Ohmmeter. The wire with resistance is the "hot" wire, the one with 1 ohm will be ground. However, if any of the connections are poor, then you will get about the same readngs, because the brake coils are low resistance. Best to wait until you can hook up to your tow vehicle, test for the presence of voltage.

I'm surprised that the Service Manual doesn't show the color of the wires. Brakes are pretty important. And having both wires that come from the brake drums colored red doesn't seem like the best idea.

Inland RV Center, In · 05-10-2013, 07:57 AM

Quote:

Originally Posted by jerryc41

I'm surprised that the Service Manual doesn't show the color of the wires. Brakes are pretty important. And having both wires that come from the brake drums colored red doesn't seem like the best idea.

The color of the wires coming from the brake backing plate are totally meaningless.

One of the wires goes to ground, and the other one goes to the brake line.

Electric brakes are not polarized, therefore it makes no difference which wire goes to ground or the brake line.

Andy

jerryc41 · 05-10-2013, 10:22 AM

Quote:

Originally Posted by Inland RV Center, In

The color of the wires coming from the brake backing plate are totally meaningless.

One of the wires goes to ground, and the other one goes to the brake line.

Electric brakes are not polarized, therefore it makes no difference which wire goes to ground or the brake line.

Andy

Right, but I don't want to connect the hot wire to the ground on the brakes, and vice versa.

One wire from the B-A switch will go to power, and the other will go to one of the brake wires, but which one?

idroba · 05-10-2013, 10:33 AM

One of the wires goes to ground, and the other one goes to the brake line.

Electric brakes are not polarized, therefore it makes no difference which wire goes to ground or the brake line.

As Andy says, either wire from the magnets can go to ground, the other goes to the + 12 volts. It does not matter which.

jerryc41 · 05-10-2013, 10:51 AM

Quote:

Originally Posted by jerryc41

Right, but I don't want to connect the hot wire to the ground on the brakes, and vice versa.

One wire from the B-A switch will go to power, and the other will go to one of the brake wires, but which one?

Here's a picture of the wires. The cable contains two wires, a black and maybe a yellow. Each wire is connected to a red wire that runs to the brake drum. What I want to know is where to connect one of the wires from the breakaway switch.

Inland RV Center, In · 05-10-2013, 10:58 AM

Quote:

Originally Posted by jerryc41

Right, but I don't want to connect the hot wire to the ground on the brakes, and vice versa.

One wire from the B-A switch will go to power, and the other will go to one of the brake wires, but which one?

Go to Radio Shack and buy a cheap VOM, which is a volt-amp-meter.

It will also have a resistance measurement settings as well.

They are cheap, informative, andd you will wish you bought one 20 years ago.

When you have it, measure the reistance to ground from each wire.

The wire that says ZERO ( 0 ) is the ground. The other wire will be a low resistance in the order of one (1) ohm or so.

Ohm,is a unit of resistance measurement.

Now you can check AC, DC voltages and resistance of many things in your trailer as well as your tow vehicle and home.

Otherwise your question can go on and on and on, and all without an answer.

Andy

jerryc41 · 05-10-2013, 11:45 AM

Quote:

Originally Posted by jerryc41

Here's a picture of the wires. The cable contains two wires, a black and maybe a yellow. Each wire is connected to a red wire that runs to the brake drum. What I want to know is where to connect one of the wires from the breakaway switch.

The Service Manual shows a yellow wire running from the trailer connector to the brakes. That's probably one of the two I have at the wheels, but there's not much color left in it. The Manual doesn't show the black wire.

jerryc41 · 05-10-2013, 11:46 AM

Quote:

Originally Posted by Inland RV Center, In

Go to Radio Shack and buy a cheap VOM, which is a volt-amp-meter.

It will also have a resistance measurement settings as well.

They are cheap, informative, andd you will wish you bought one 20 years ago.

When you have it, measure the reistance to ground from each wire.

The wire that says ZERO ( 0 ) is the ground. The other wire will be a low resistance in the order of one (1) ohm or so.

Ohm,is a unit of resistance measurement.

Now you can check AC, DC voltages and resistance of many things in your trailer as well as your tow vehicle and home.

Otherwise your question can go on and on and on, and all without an answer.

Andy

Yes, they do come in handy, and I've had several for years. I'll give that a try.

jerryc41 · 05-10-2013, 04:56 PM

Quote:

Originally Posted by jerryc41

Yes, they do come in handy, and I've had several for years. I'll give that a try.

I posted a reply and two pictures, but I don't see them. Long story short, I used the meter on the wires at the brakes - the black and the yellow. Each one gave me a strong swing of the needle over to zero.

Splitrock · 05-10-2013, 05:00 PM

Jerry, If I read your posts correctly, it looks like you are toying with the idea of connecting the breakaway switch to the brake magnet wires. That's not how the breakaway switch connects on my trailer. Not even close.

jerryc41 · 05-11-2013, 05:29 AM

Quote:

Originally Posted by Splitrock

Jerry, If I read your posts correctly, it looks like you are toying with the idea of connecting the breakaway switch to the brake magnet wires. That's not how the breakaway switch connects on my trailer. Not even close.

I'm surprised that Airstream wanted to keep the brake wiring and breakaway switch wiring a secret. 1973 wasn't that long ago. I think I'll just leave it as it is - unconnected - and let the new owner find someone who knows how to connect it. A week from tomorrow, it will be sold.