Postwar horn relay question

The entire relay and horn must be taken off the frame and the mountings points cleaned of any dirt or corrosion. The relay bracket contact for the battery must also be taken apart and cleaned as well as the battery plate on the bottom of the frame. The lower moveable relay contact may need to be removed and cleaned also, including especially the rear part where it hinges on the relay frame. The relay frame at that point must be cleaned also. This may stop the 'hanging' of the contact also. In essence, the entire path for the battery voltage needs a perfectly clean path to work consistently due to the low voltage being used.

Larry

Sounds like you have more than one problem going on at the same time.

1) The relay being stuck could be from the coil becoming magnetized. A thin piece of tape between it and the plate will sometimes cure this, but the contact for the horn circuit may need adjusted afterwards.

2) "The horn will not work at all when it does that."

With a battery installed and the engine off of the track, will the horn work if you lift the plate manually?

Do you have a multi-meter to check any of these problems? If so;

> Check voltage across the contacts when closed, especially when it's stuck in the up position. If you get battery voltage and no horn, try sliding the plate around a little and see if it improves.

> Check for continuity throughout the horn circuit (ohms function - without battery, or voltage function - with battery, working from a solid frame ground point).

Larry gave some good pointers, but I would try this before disassembly, unless you don't have a meter.

Good luck,

Dave

Chuck, didn't see you posted about the relay.

Well, I really appreciate all the responses. Here's what I did......dismantled the front of the relay and cleaned everything. Dremel, contact cleaner, sandpaper. Reassembled and the relay isn't hanging up (for now). On to the horn.  The horn still doesn't work right. Then....the wire going into the horn broke off right at the horn. So.......major surgery because I had nothing to lose. Opened the horn (I know that's not supposed to work, but had nothing to lose) and lo and behold.....corrosion on all the contacts inside. Dremeled, contact cleaner and then unwrapped on coil of wire from the coil and fed it back out. Reassembled the horn without breaking any tabs. Connected to a D cell and.....BINGO. It works. Adjusted the screw to taste. Whether it works later when I get it back in the engine and on the tracks is another story. That will have to wait till much later tonight, but I will be back to you on the results.

I was out in my shop working on it and did not see your posts about the electrical tape and meter readings. If it works when I put it back together, I'll leave it be. If not, I'll disassemble the relay and add the tape and do some readings.

Many thanks,

Roger

I'm thinking the problem is the relay. When I connect a D cell directly to the horn, it works now (post surgery). But the relay is still flukey. I'm not getting battery voltage when I measure with the meter on either side of the two relay contacts. The plate is definitely magnetized. It hangs up there. I'll put some tape on the plate and see if that does the trick. But....I don't know why I'm not measuring battery voltage when the contacts are closed. ??

Roger

Battery voltage will be measured between the moveable contact and ground with the relay unpowered. With the relay closed, you should measure battery voltage between the horn wire and ground with very little voltage drop with a fresh battery. See here for a schematic. If you have not dis-assembled and cleaned the top battery contact from the relay, do so also.

Larry

Well. Larry......it's 2 AM and I finally got it working. Whether it works tomorrow is another story. I'm convinced it was the relay. I took it apart several times. The contacts came together but not with enough force to blow the horn well. So....bending the contacts and reduced the size of the piece of tape I put in because the plate was magnetized. The real test was whether it would work with my sound buttons and it did. They don't have the 5V boost. I'm thinking the relay is a bit weak and at some point I'll probably replace it, but if it works tomorrow like tonight, I'll be satisfied. Thanks for the advice to everyone who contributed. It all helped.

Roger

Worked on it again this morning. I discovered that I have a contact problem with the bottom cover of the battery compartment. It's not making good contact with ground. What I finally did was run a jumper wire from the slotted screw that holds it down to the e-unit attachment screw. No other sites was giving me clean conductivity. Now the horn is strong.  We'll see how long this lasts. When people say these things are finicky, that's an understatement.

Roger

Where did you learn that using sandpaper on relay contacts is a good idea?

Is that not a good idea?  I've always used it and never had a problem. They always worked better after a light sanding and then a spray of contact cleaner.

Here is what I do to clean relay contacts, doesn't matter whether they are in trains, pinball machines, or elsewhere:

 moisten (don't soak) a business or index card with mineral spirits or contact cleaner

 rub it back and forth between the contacts while gently holding them closed

Sometimes a dry card is good enough.

For really bad contacts, I use a brush style fiberglass eraser.

Dave,

I thought I had good contact because I Dremeled and sanded and thought.....can't be. I was wrong. A lot of time went into fixing this, but it boiled down to three things that made the most difference. I bent the battery frame downward to press harder on the battery. Two.....the first huge difference was the jumper wire I ran from the screw on the battery compartment up to the e-unit attachment screw. Three.....the jumper wire from the top of the battery contact to the underside of the armature. With the last, I didn't notice a difference in volume, but as the train jiggled along over switches and UCS tracks, the tone of the horn would change. Now it doesn't.        When I got a loud sound out of the horn by directly alligator clipping it to the terminals of a D cell, I knew it had to be bad contacts.  And we had great ideas and help from all the folks who contributed to this thread.

Roger

PennsyDave,

 The trick with the switcher horns is the battery. Look closely as you insert the back end in the bracket. The 'C' batteries made today have a rolled end, that is the back of the battery is not making contact with the battery bracket because the rolled edges of the battery tube is touching the bracket, not the rear of the battery. If all else is good try just inserting the battery half way into the battery bracket.

I am using a Duracell and it is definitely in contact at the bottom.  The relay works, the bottom jumps up when blowing the horn and the motor speeds up due to the increase in voltage but I get nothing out of the horn. The adjustment screw does not move at all.  I need a bigger pair of pliers.  I hate to take the horn face off again because I know all the tabs will snap off.  I already broke one the first time.  

How do you check just the horn?  If I put the hot lead of the horn to the pos side of the battery and ground the other, should the horn blow?  

Thanks for all the help,  This is the first horn work I have done.  

Dave, the horn should definitely blow powered directly from a new battery. Put the battery negative directly on the metal horn case itself, and the horn coil wire to the positive terminal of the battery. If it does not blow, check continuity through the coil winding to the horn metal case.

Larry

Dave,

See if you can find some nut driver bits. At the very least, an adjustable wrench. A pair of pliers on that tiny nut is asking for trouble by rounding it off. Even if the horn is good after cleaning it internally as you did, if the adjustment screw is way off, you'll get nothing out of it.

Roger

Thanks for your help, I now understand the horn, but no luck.  I just get a small very short chirp when I power the horn.  The relay works fine.  Thanks for all the help but I think this one needs a new horn mechanism. I can't move the adjustment screw at all. Customer doesn't want me to spend any more time on it.  I believe the screw had been rounded off earlier, my nut drivers would not fit properly.  

Let's face it, these horns weren't the best in the first place.  I have a FM Trainmaster that the horn sounds great on!  

Since you have nothing to lose with it....why not hit the screw with WD-40 and then grab it with a Vise Grip?

Roger

Roger,  May try that, WD-40 is one of my favorite tools!!  Will let you know and thanks again.

Dave,

I worked on three of these horns in the last few weeks and this one (reason for the thread) had a stuck screw like yours. All of a sudden, it popped free. Probably corroded in place. But if the horn doesn't work, you have nothing to lose, really. Give it a shot.

Roger

When the horn just 'chirps' when connected to a C/D cell, I've found connecting it to a 9V momentarily, 1 or 2 seconds, will often break internal corrosion loose and get it working again.

Dave,

When you opened up the horn to unwind wire from the coil, did you clean the contacts in there?

Roger

Roger:  I cleaned the center contact on the internal horn 'spacer' but that was all, everything looked really clean in there.  

Len, Tried a 9 volt battery, nothing.  

Used vice grips to turn the adjustment screw a bit, still nothing.  Horn needs more help than I can provide. This was a well used engine with little lubrication and the brass worm gear's teeth are partially worn down.  Must not have been in a loving home! 

Thanks for all the ideas!