Fixing electric contact

[TEXASAPPLE]

I have a new DCC equipped F7A to replace one that recently broke.  It ran sporadically when I first got it on a layout which had given me no previous problems.  Current was going to all sections.

Got out some older track and ran the loco on it for awhile.  Looked like it was broken in, but back on the layout it won't run.  Tried it back on the other track with no luck.  Cleaned all track.  No go.

Occasionally, the headlight will come on, but never fully.  Somehow juice is not getting to everything.  Are there some "fixes" which I can attempt?  I really liked my old F7 and hope this one will be just as faithful, but not running, it's just a doorstop!!

[James in FL]

Hi,TEXASAPPLE,

Check the wipers where they contact the frame, the loop part.
They are fragile and will break with repeated bending.
Do you have access to a multimeter?

[TEXASAPPLE]

Yes, I have a multimeter.  The wipers are located where?

[TEXASAPPLE]

Since my last reply, I pulled out my schematic of the engine and I assume you mean the wipers in the trucks.  I am hesitant to take the engine apart (prior bad experiences).  Is there some way to fix this without taking it apart?

[brokemoto]

Do you use DC or DCC?   These things have allegedly "smart" decoders that are supposed to operate either on DC or DCC.  I do not use DCC.

I have had four B-mann decoders fry on DC.   Once I took out the decoder and connected the wires appropriately, the locomotives ran well, again.   I have fried decoders both on straight DC (or as "straight' as rectified DC can be) and pulsed DC.   In three of the cases where the decoder fried, the locomotives were running along the track and suddenly stopped.   I tried fiddling with them, no results.  When I took off the shell and applied current around the decoder, the motor turned.   I figured that something had happened to the decoder, so I took it out, reconnected the wires and the locomotive was once more in service.   In the fourth case, the decoder fried when I forgot to change the polarity on a reversing loop.

One of the locomotives that fried its decoder for no visible reason, was, in fact, an F-7.  One was a ten wheeler, the third a 44 tonner.  I fried the decoder on a 70 tonner when I forgot to reverse the polarity on the reversing loop.

I am wondering if your decoder has fried.

[Ken G Price]

Have you cleaned the wheels?

[TEXASAPPLE]

I have cleaned the wheels and the track, but will check both again.

[James in FL]

Yes, the wipers are in the trucks, you don't have to necessarily disassemble the lokie, you just need to remove the trucks.
IIRC the F7 utilizes wheel back wipers. Clean the wheel backs and the wipers where they come in contact.
With your multimeter check for continuity here.
Then check from the wheels (wipers) to the frame.
Also check where the board comes into contact with the frame at those tabs that hang down from the board.
Continuity Yes? No?