Forest River Impression – AC Capacitor & Fan Motor Service

Living full-time in an RV changes your math on repairs fast. You start calculating the cost of parts versus the cost of a mobile tech, and you realize that most of these jobs — once you understand the system — are absolutely within reach for someone who’s willing to read a guide, watch a video, and take their time. On the Forest River Impression, the rooftop AC unit is one of those systems you cannot afford to ignore — when it starts humming, struggling to kick on, or the fan stops moving air altogether, the culprit is almost always a failing run capacitor or a worn-out fan motor, and in the middle of summer, that’s not a comfort issue, it’s a livability crisis. The good news is that both repairs involve straightforward components that cost a fraction of a service call, and with the right steps, you can have cold air blowing again the same afternoon. This guide walks you through exactly how to diagnose which part has failed, how to safely replace it, and what to double-check before you button everything back up.

The Capacitor That Brings Your Forest River AC Back from the Dead

The dual run capacitor is the single most common failure point on Forest River rooftop units — when it goes, your compressor hums but won’t start, or the fan motor spins weakly and the unit cycles on and off. This $25 part is what’s actually telling your motor to fire, and once it’s tired, no amount of thermostat tweaking will fix it.

What works

• AC kicks on immediately and holds — no more waiting 30 seconds for the compressor to engage or hearing that dead-man hum.
• Fan motor runs at full speed instead of that anemic crawl where you’re barely getting any cold air through the vents.
• Swaps in under 10 minutes once you’ve discharged the capacitor — no special tools, no EPA certification needed, just two wire terminals and a bracket bolt.

What doesn’t

• Amazon’s two-day delivery doesn’t exist when you’re parked in 95-degree heat — you’ll be ordering from a parts supplier and waiting 3-5 business days, so catch this failure early.
• If your AC unit is a vintage Atwood or Penguin unit, this Dometic-spec capacitor may not be a direct swap — you need to verify microfarad ratings (µF) and voltage match your original exactly.

I second-guessed myself on the first replacement because the new capacitor looked physically identical to the dead one, but the AC was still running weak — turned out the shroud gasket was also cracked and pulling warm air back in, so never assume one fix solves it all. Order the RV AC dual run capacitor (Dometic/Coleman-Mach) and test it in the shade with a temperature gun before you assume it’s not the problem.

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