HO GP40 Motors - Constant Screeching - FIXED!

[PrairieDub]

I'm experiencing a constant "screeching" sound from a Bachmann HO Scale EMD GP40 Diesel Santa Fe Flyer DCC that came as part of the Bachmann Commander set.

I've stripped the unit to base components and lubricated everything. All parts are turning freely.

Could this be a problem a problem with the DCC controller onboard or is it a mechanical problem?

Thanks!

[Joe323]

If you are referring a hum it is coming from the decoder.  Bachmann DCC on Board locomotives uses a low-end decoder that makes a hum. Short of replacing it with a better one I don't know if anything can be done.

[PrairieDub]

Thanks for the input. This is much more than a hum...it's a horrible screech. I swapped the decoder board from another Bachmann loco that runs perfectly quiet, but the problem persists in the original loco. So, I don't think it's the electronics, unless they're causing the motor to screech somehow?

I've got to say that I'm really disappointed that Bachmann Quality Control allows a brand new loco with a huge problem getting to a customer. This problem could easily have been caught with the simplest of QC checks.

Positives: I enjoyed stripping it down and most of the components seem to be reasonable quality.

Negatives: Soldering of the wires looks like it was done by a 10 year old in a hurry, and a couple of soldered connections broke off during disassembly and handling.  Make sure you have a soldering iron handy if you're going to take apart.

Overall this is a BIG Bachmann fail...1 out of 10 (1 is generous)

[Joe323]

Okay that does sound mechanical in nature.  Have you contacted the service department?

[PrairieDub]

I haven't contacted Bachmann. I figured that once I've taken it apart it the warranty is voided?

[Joe323]

I do not think so but call.  Even if is they only charge $35 maximum (last time I checked for service) and they warranty repairs or replacements for one year so it's worth a shot.  Maybe you can speak to a technician and they can tell you what to do over the phone.

Can't hurt to ask.

[dutchbuilder]

Did you oil the motor axle.
If the axle is dry and the bearings are a little warn you get an awful screeching noise.

Ton

[the Bach-man]

Dear PD,
It sounds like it needs lubrication.
Try that first. Light lube won't void the warranty.
If that doesn't work, call the service department.
Good luck!
the Bach-man

[PrairieDub]

Thanks BM

I've checked both gearboxes and made sure they're lubed and turning freely...I've turned the worm gear with my finger and made sure the plastic gears are turning the wheels. No resistance, I think they're good.

The motor is sealed, so How can I lube the motor shaft bearings? Can I apply contact cleaner to the motor bushes?

Could bad / intermittent electrical pick up from the wheels to the contacts (H61207-1) cause the motor to whine / screech?

[dutchbuilder]

Just put a little drop of oil where the axle comes out of the motor housing on both sides.

Ton

[Len]

These are a bit unusual, but at one time or another I've seen them all.

With the shell off, but otherwise assembled, check that you don't have a truck mounting screw that's too long and rubbing on a drive shaft on one or both ends. Also that there's no metal "flash" on the upper or lower chassis pieces rubbing the drive shaft connectors on the motor. If neither of those is the culprit, try running the motor with nothing connected to it. If it screeches, even after being lubed, you probably have an internal brush holder that got folded under itself. Not much can be done about that, except replace the motor.

Len

[PrairieDub]

Thanks guys, I appreciate all the useful input!

[PrairieDub]

The Santa Fe GP40 is now spinning quietly like a champion!

I tried many things to stop the screeching. I'm not 100% sure but, lubricating the motor shaft (as described by Len in this thread) seems to have fixed the problem.

I removed the motor and ran it unloaded on the bench, no screeching. I noticed that when I reassembled the unit...if I left the 2 castings screws slightly loose it helped. Then carefully seating the motor I think I found a "sweet spot" that allowed the 2 casting to mate without any squeezing required...Maybe there was some misalignment???

Thanks for all the quality input!

[rich1998]

Very good troubleshooting. All part of model railroading.

Rich

[PrairieDub]

I've disassembled this GP40 so many times I could probably do it blindfolded!