2338 GP7 Horn Advice

[northernpike]

Question for owners of the PW 2338 Milwaukee Road-  Seems to be a great engine except for Horn.

Horn does not work-baffled as to why!

I put a new d cell positive to the horn wire, grounded the case and got a click.  Adjusted screw, got the horn to sound well.  Thinking all was well, I resoldered the horn wire to the relay.  Nothing from the horn.

Checked relay, working great.  Battery contacts clean.  Should I adjust the screw again with wire connected to relay and whistle lever on?  Transformer is a 1033.  All my other whistles/horns work well.  Stumped as to why it won't sound on 2338.  Help?

Thanks much

Tom

[servoguy]

 Tom,

you failed to find all the relay contacts.  The obvious one isn't the only one.  The armature is not securely wired with a short jumper to the relay frame.  I usually solder a short piece of wire between the armature and the frame to make sure there is a good contact between the two.  Use something flexible.  This is usually not a problem with a whistle tender because the voltage is much higher, but with only 1.5 volts from the D cell, you have to make sure all the connections are very good.  I had the same problem with a 2343 when I brought the horn back to life.

Bruce Baker

[RockIsland52]

Reminds me, I've been meaning to pull out my 2348....same problem.  Maybe this thread will light a fire under me.  Good stuff.

Jack.

[northernpike]

Bruce

Thanks for the info.  Have a couple more questions.

I checked all the contacts on the horn relay-good solder points.  Everything is wired ok according to the wiring schmeatic.  Which part of the armature do you add the jumper to?

Do you also solder the frame end directly to the relay frame?  I have superflex for wire.

Thanks again

Tom

[hscsltb]

A little while back CTT ran an article on horn repair.Late last year maybe.Im not at home so I cant look it up for you right now.

[servoguy]

 There needs to be a good connection between the relay armature (that is the part that moves when the relay is energized) and the relay frame.  The relay frame is grounded to the frame of the locomotive by the mounting screws.  If you look, you will see that there is no really good connection between the armature and the frame of the relay.  Solder a wire between the two, but remember that the armature must move when the relay is energized.  Also, check all the other connections for zero resistance.  When you are done, you should have 1.5 volts across the relay contacts, and if you close the relay, you should have 1.5 volts from the frame of the engine to the wire that goes to the horn.  Make sure the connection between the case of the horn and the engine frame is good.

If you still have trouble, draw out a circuit diagram and check the voltages around the circuit with the relay closed.  If the horn doesn't blow with the relay closed, you will find a voltage where there should be none.  On your circuit diagram, write down the voltages you expect to see relative to the engine frame.

Bruce Baker