Stopped Trane with a crack

[atufano]

Had a no cooling call Friday at 8 PM. Intermittently shutting down the Air Handler. A/H is a Trane. We don't see many of these units out here. Why? I don't know. Usually we run into P.O.S. contractor or hack specials.
Anyway. This unit is 15 years old. I poke around and find this little spark coming from this PCB.

http://home.hvc.rr.com/hackpics/DSC00227.JPG

Curious, so I pull it and I find this.

http://home.hvc.rr.com/hackpics/DSC00230.JPG

If you look to the left of the picture, you'll see where the PNP Transistor is mounted to the PCB.

I'll be damned. That little transistor has a cracked solder joint. So, then I found a really good use for Stay-Brite. Field fixed that puppy and it was up and running in 10 minutes.

Now, does anyone know where to get this PCB's? What is their purpose? The condenser was running when I got there and the coil was starting to ice up. Who carries them, or can you just get rid of them or what can you use to replace them? It connects to the Fan Center relay and then has two other wires to connect to them. And oh yes, it's a heat pump too.

[a\c don]

That CB controls blower on-off delay.

Its available from any Trane/AS supplier.

[Edmund Forsthe]

the question is why did it crack a replacement will probably crack also in due time, is it because the board was not mounted on isolation mounts

[markwolf]

Originally posted by Edmund Forsthe
the question is why did it crack a replacement will probably crack also in due time, is it because the board was not mounted on isolation mounts That is the most common pcb failure there is.I saw first hand when I used to hang out at my buddies tv shop years ago.I would say %90 of the repairs he made were on poor solder connections.It seemed worse on boards made in mexico.....Inferior solder?You tell me.

[atufano]

Originally posted by Edmund Forsthe
the question is why did it crack a replacement will probably crack also in due time, is it because the board was not mounted on isolation mounts

The fan center relay is mounted to the panel box case and the PCB is connected to the fan center, kinda just hangs there. It's weird that only one solder joint cracked and not the joints holding the PCB to the fan center.

[tecman]

Not so unusual. The crack appears to be at the location of one of the spade lugs. Mecganical stress from the attached wire plus some vibration and heat make a perfect combination for a fatigue crack like that. Board is otherwise most likely perfectly OKay.

paul

[dandyme]

Isolate the Hot
forget the board it`s 15 yr old
plug fan & com to the 911 relay
let everything else be

that machine won`t know the difference

I give the HO the option.

[Swampfox]

Originally posted by dandyme
Isolate the Hot
forget the board it`s 15 yr old
plug fan & com to the 911 relay
let everything else be

that machine won`t know the difference

I give the HO the option.

Ditto, those boards have a very high failure rate, usual failure is the fan wont turn off or a clicking noise