# 302 AC help



## ennisdavis (Dec 9, 2018)

I am working on a 302 ac. Cleaned the commutator. Tender not connected, a/c to the brushes should turn the motor over, right? Turns freely lust wont run with power. The brushes look good.


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## AmFlyer (Mar 16, 2012)

These engines have series wound universal motors, the armature is in series with the field. So putting AC across the brushes will not cause the motor to run. Take a look at the wiring diagram on the Port Lines site. It is in the AF repair clinics section. You can see which two of the four pins on the back of the cab will work to run the motor without the tender reversing unit connected.


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## T-Man (May 16, 2008)

*You tested that and it did not work*

Does the engine have the four hole jack?

Some do not and are connected to the tender with four wires.


The four wires are two brushes and two from the field. using a jumper connect a field wire to a brush. Then with the transformer touch each wire to the other two. It will go in one direction. By switching the transformer wires it will reverse direction.

If you have the jack use it and place the jumper wire in the holes. Just trace them back.


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## cramden (Oct 13, 2015)

AmFlyer and T-Man are correct. The easiest way is to jump the two inner holes together on the jack panel and the two outer ones are for the base(left hole) and variable(right hole) wires from the transformer. That should get the motor to run.If not, then you'll have to look for other problems.


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## ennisdavis (Dec 9, 2018)

Thanks, works like a charm, Didnt see the field winding under the motor.


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## cramden (Oct 13, 2015)

Glad it worked. Welcome to the Forum. Have fun with your "Flyers".


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## T-Man (May 16, 2008)

Wohoo!! :smilie_daumenpos: :smilie_daumenpos: :smilie_daumenpos:


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## ennisdavis (Dec 9, 2018)

Now for the trick question. Looking at the top of the rotary switch, what should it look like for forward motion. I want to lock it into that position.


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## T-Man (May 16, 2008)

Trial and error. you need to lock it when it is in neutral and the next direction is forward. Positions cycle forward, neutral, reverse, neutral, and back to forward.


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## flyernut (Oct 31, 2010)

302AC, one of my favorite engines, I think I have a gazillion of them,lol...Your 302AC should have head-light, smoke, and choo choo. These are great little engines, and should last another 60-70 years with a minimum of maintenance..Good luck with it.. Check out some of the many 302AC threads here on the S scale forum.....forgot to add, WELCOME!!!!


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## ennisdavis (Dec 9, 2018)

*different direction*

So I have 2 engines and I tried the center jumper on the pins to get the engine running. One runs forward and the other in reverse. How can I get the engine to run forward?


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## cramden (Oct 13, 2015)

Switch positions of the outer wires from the transformer going into the fiber board. That will change the motor direction.


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## ennisdavis (Dec 9, 2018)

wrong, its a/c.


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## T-Man (May 16, 2008)

Did you try it? Some arrangement will make it go forward.


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## cramden (Oct 13, 2015)

ennisdavis said:


> wrong, its a/c.


I'm aware it's ac. I should be more clear. I forgot that you have to switch the jumper from the inner holes to the outer holes and run the two transformer wires to the inside holes. That uses the opposite brush and field wire to reverse the current. Here's a pic of a 4 wire engine, it should make things more clear.






Hopefully I have it right this time.


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## ennisdavis (Dec 9, 2018)

yep, ac voltage has never changed since invented in 1832. no polarity, it alternates.


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## ennisdavis (Dec 9, 2018)

fixed it. should have known. i swapped the brush connections. now on to no smoke condition. any thoughts.


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## T-Man (May 16, 2008)

Get an ohm reading on the resistance in the smoke box.


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## flyernut (Oct 31, 2010)

If no smoke, just re-build the unit, fast, easy, and cheap.. I don't muck around with them, I just re-build them if little to no smoke.


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## ennisdavis (Dec 9, 2018)

What should the resistance be and how many drops should I put in the stack?


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## flyernut (Oct 31, 2010)

ennisdavis said:


> What should the resistance be and how many drops should I put in the stack?


I don't know what the resistance should be, but about 10 drops should be plenty to test it out. Let it soak for a few minutes that add power.


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## Kelpieflyer (Jan 9, 2012)

Resistance should be around 35-40 ohms. I wire mine to about 38 ohms and they last a long time. Haven't burned one out yet.


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## flyguy55 (Apr 20, 2015)

Early 302 AC project for sale in Forum sale board....


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