A/C Capacitor Problems

Question

Well, I am five days into RV ownership and I have a problem with my A/C compressor not coming on. The thermostat will kick the fan on, but compressor will not start.

I had this same thing happen to my Dad's 5'er a few years ago so I immediately went up and checked the capacitors. Sure enough the Start cap had its top blown and I believe that caused a hole to be melted into the side of the run cap. So I bought new caps and will be replacing the original start cap with the common SPP6 Hard start kit while I'm at it, but one thing that seemed odd is that there is a printed circuit board mounted under the cover with the capacitors, is this normal? The reason I ask is because my dad has what seems to be the same unit, but he has no PC board next to capacitors. Does this make any difference when replacing the original start cap with the Supco SPP6?

Also, for anyone who has done the SPP6 upgrade how did you mount the new LARGER cap since it appears it won't fit into the original metal enclosure. Suggestions please.

Thanks for the help,
Jake

**Note I will edit with model number of the A/C Unit when I get the numbers.

j_robinson389 · Answer

Well, I still didn't think to grab the model number off of the unit, but I did figure out what the PC board was mounted next to the caps was.

It is a 150 second (2.5 min) delay circuit. When power is applied, the blower fan kicks on immediately then 150 seconds later the compressor kicks in. Is it just to prevent the compressor from cycling off then back on too soon? The reason I ask is that with the delay circuit board in there there is not enough room to mount the new start and run caps that I put in.

tachdriver · Answer

Are the capacitors accessible from the inside or outside?

chris_bryant · Answer

Some models have the circuit board in the roof unit, some in a separate enclosure. Are the fan and compressor connected to the board?

j_robinson389 · Answer

Capacitors are in an enclosure on top of roof under the A/C shroud.

The delay timer is only hooked to the compressor, I assume it's purpose is to protect the compressor from turning back on too soon after shutdown. The fan will come on immediately, but the compressor waits 2.5 min to kick on.

bill_t · Answer

The small attached board could be working as a relay (timer) to take the start capacitor out of the circuit once the compressor is started.

The compressor start time delay could be coming from the unit control board.

T'stat calls for cooling, sends signal to control board, control board starts fan and starts timer for compressor, control board times out sending signal to compressor to start, compressor starts, when compressor motor is up to speed start capacitor board takes start capacitor out of circuit.

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