The C-19 I've been working on has a large fan in the back of the tender. I've never seen it running. Does it get triggered by some heat sensing circuit?
Anyone removed the fan and replaced it with a smaller one?

Fred,

I run batteries and have removed any and all fans w/o issue. i do not recall one in the C-19 tender thou.

Al P.

The fan was there to cool the electronics, per Bachmann... but sometimes it is installed backwards and blows in a direction that does not help cooling.

Most people toss it.

I have been running my Bachmann Climax whose fuel and water tank is packed totally full of electronics, which does have mounts and plug-ins for a fan, on continuous runs for hours at a time, in full sun on days with temps over 100 and no fan without any noticeable problems. Surface temperature on the oil tank top has reached 140 degrees at times, though more typically shows around 120.

Besides draining my batteries faster, I'm not too sure having a fan blowing those kinds of temperatures around the electronics is likely to help much?!?!

Fan helps, you just are not hot enough yet! 

Quote from: Greg Elmassian on October 10, 2026, 02:42:27 PMThe fan was there to cool the electronics, per Bachmann... but sometimes it is installed backwards and blows in a direction that does not help cooling.

Most people toss it.

So which way is correct?  Input or exhaust.

Direction doesn't matter. What matters is that there exists another "opening" for the air to intake(fan exhausting) or exhaust (fan intake). Electronics don't care whether air flow is left to right, right to left, etc. It just has to be flowing otherwise you're simply trying to pressurize or de-pressurize the inside and that's not what a fam is for.

Actually, direction does matter... in some use cases...

so sucking in air is preferred, because if the smoke unit is used and you have the fan "exhausting" people have reported it pulls the smoke into the loco, not out the stack.

other than that then normal electronic cooling rules are in order, and then you should be exhausting air, but the difference here is small.

if you look at modern electronics, a fan mounted to the case will be exhausting, pulling hot air out along with any heat from the fan itself... but in this case the fan's heat is minimal..

But, in the very specific case of this loco, the most important thing is as wraujr stated (sort of) just a bit of airflow over the "hot" device makes the most difference..

Spent a number of years with real products (a small company called Hewlett Packard) in the 70's when we really started looking at what the heck the fan was doing...

so, will you use smoke? then the choice is easy..

" if the smoke unit is used and you have the fan "exhausting" people have reported it pulls the smoke into the loco, not out the stack."
Yes, that would change the exterior effects if the direction can effect smoke generation, second hand.
More likely points to not enough inlet air surface area. Proper/balanced airflow requires equal in and out.
But in case of cooling with little heat added by fan, as long as inflow and outflow effective area are balanced direction doe not matter.
That said, fan direction can be affected by the "order" in which the airflow crosses the electronics.
Typically you want the air to first encounter the non_power electronics to maximize their cooling and then cross over higher power components (think power supply) as you want the higher power components downstream. Spent of number of years in small military companies designing for harsh environments.

Yeah an interesting area of packaging design... now involved in passively cooled 10 gigabit switches, and those lasers in the fiber optic transceivers are tough to cool!

fans are easy when you start to conductively cool stuff never designed for that method of cooling.

(the video does not show the "secret sauce" of cooling)

https://www.youtube.com/watch?v=5zXA1bh4dLI