Model Railroading > Question about Intermountain’s HO AC12 performance

I have an Intermountain AC12 that I bought several years ago. I had the drive mechanism upgraded and decoder replaced with a Loksound by Intermountain. The model runs great but has seen little operation. How has your model held up over the years of operation.

I had mine upgraded to but did not upgrade the decoder because I talked with soundtraxx they said it was not the decoder it was the motor. I used it at the club with two AC12 pulling 80 cars and failed do to overheating the decoder.. After the upgrade same train staled on a 2 percent grade but did not over heat. I still have the 2 and have not sold them because they are very nice models but they are not made as intended in real life. Ha Ha hope this helps Oh when I got one of the locos back after the upgrade one was missing a number board but I noticed it a year later because as collector I do not check everthing. but I am now checking every thing when I get a model.



Edited 1 time(s). Last edit at 07/27/20 22:33 by bnsfmodeler.

If you want to see how bad it can get, read Jason Hill's blog entry regarding his history with Intermountain AC-12s. That said, I hope my 3 fair better than his.IMRC Cabforwards - 10 Years of Experience (linked)

It's a real horror story, but you have to remember that he's operating them in a pretty demanding environment - the famous La Mesa club in San Diego.

Arved Grass
Fleming Island, FL

I skimmed through the linked Jason Hill blog and it seemed to conclude with the 2nd run IMRC Cab Forwards.  No discussion of run 3, which were further improved from what I understand.

On my modest sized home layout the original (never upgraded) version does just fine.  It pulls trains that fit my sidings (14-15 cars on 2%) and the slow top speed is fine with my 36" radius curves.
And I think it sounds just great.
I have gotten to understand Soundtraxx decoders and Loksound confuses me so I really don't want anything to change.

I purchased a first run and it was a dog turd.  I sent it back, they "worked on it" and sent it back to me.  Still ran terrible.

Intermountain finally got everthing fixed by the third run and offered a "rebuild program".  I sent it in, as did LOTS of other people, so it took a while.

They replaced the motor and transmition, free of charge.  They would replace the gear box and all the drivers to phase 3 versions for about $100 and put in a Lok sound decoder instead of the Sound Trax for about another $100.  I went for the works.

It is now the locomotive I expected.  It pulls great, runs great, and sounds great.  The only way I would purchase a phase 1 or 2 is if I got it REALLY cheap knowing I would have to send it back to Intermountain for upgrage.  

So to sum it up, run 3 and newer are great, older ones need to be sent back to Intermountain for upgrades.



Edited 1 time(s). Last edit at 07/28/20 20:46 by JimMRL.

I thought IMRC has, to date, only made 3 runs of the Cab Forward.  I believe a 4th run is planned according to their website.

Run three allegedly correct the the issues of runs 1 and 2, and also run 3 used the Loksound decoder as opposed to runs 1 and 2 which used Tsunami.

Thanks for your response. Yes, I sent mine back and they did the works. I appreciated their offer to help make corrections and I went with the Loksound because I thought the sounds were better. The last run I bought the 4294 since I would always see it in the museum in Sacramento. The 4294 seems to run well on my garage layout. They sure look nice. Thanks again for the info.

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My N-Scale AC runs when it wants to, which is not all the time. Looks great though!

Bill Deaver
Tehachapi, CA

MojaveBill Wrote:
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> My N-Scale AC runs when it wants to, which is not
> all the time. Looks great though.
Electrical or mechanical problem?

May I assume you are referring to the HO scale version?  If so,........

The third run of IM cab forwards (and prior runs updated to third run standards) seemed to cure ills of the first and second runs, though may have introduced a new problem experienced by a few folks.

IIRC, the upgrades to the third run included a new motor, less tension on the drivers from the contact wipers, and improved driver to axle joints (the drivers worked themselves loos on some first run models).  The third run used a Loksound decoder (a "Select," I think, but possibly a V4) instead of a Tsunami 1000. 

Some users experienced loss of control problems with their Loksound equipped cab forwards on Digitrax DCC equipped railroads.  Removing the EU mandated anti-noise capacitors was supposed to be the fix, but even that didn't work for some of us.  IM sent me a couple tenders with different Loksound decoder and motherboard arrangements to try, but they made no difference.  I gave up and put a Tsunami 1000 in mine and had no further problems.  At our model railroad club, we later installed electronic "snubbers" in all the blocks and that finally seemed to solve the problem for those who didn't switch (back) to a Tsunami 1000.

This was my experience; as the saying goes "your mileage may vary."

The description above regarding the last run, 3rdrun, improvements agrees with what I recall. I haven't heard of any issues with Loksound.

What are these snubbers installed. Elaborate please.

Posted from Android

Nice hanger queens. Sold my three off. Mine had the bad motor and IM wanted to charge me to have the motors replaced.

Posted from Android

A couple years ago I was at the Timonium train show and a gentleman there was running 100 car PFE ice reefer trains pulled by 2, maybe 3 Intermountain Cab Forwards.  I recall one was a 2nd run upgraded with new motor, maybe other parts and the other(s) was 3rd run.  They both ran well and he seemed very satisfied with them the way they were.

 

I'm not an electronics guy, so I've pasted from Mark Gurries' web site:

A "snubber" is what you might call a nickname for a Resistor Capacitor filter and is a "means to remove unwanted signals (Noise, Voltage Spikes, you name it) out of the signal you want to keep (the DCC signal)."  Link to Mark Gurries' web site below:

https://sites.google.com/site/markgurries/home/dcc-general-best-practices/wiring-planing/snubbers-rc-filter

SPDRGWfan Wrote:
-------------------------------------------------------
> The description above regarding the last run,
> 3rdrun, improvements agrees with what I recall. I
> haven't heard of any issues with Loksound.
>
> What are these snubbers installed. Elaborate
> please.
>
> Posted from Android

wnehoc Wrote:
-------------------------------------------------------
> IIRC, the upgrades to the third run included a new
> motor, less tension on the drivers from the
> contact wipers, and improved driver to axle joints
> (the drivers worked themselves loos on some first
> run models).  The third run used a Loksound
> decoder (a "Select," I think, but possibly a V4)
> instead of a Tsunami 1000. 

It was a "Select." I had a problem with one that was purchased second hand. I replaced it with a V5, as the cost difference between a replacement "Select" and V5 was minimal. I haven't had a chance to test the model since replacing the decoder due to the pandemic.

 

Arved Grass
Fleming Island, FL