2008 Discovery.I have two AC units, the front is at 1500, and the back 1350.The back has begun to spike during startup. If I am on 50 amp service I cannot see this and nothing goes wrong. On 30 amp service I see a 40-50 amp spike. It still starts as it is only momentary. However it is bad enough to shut down the GenSet as it sees the spike and shuts down to protect itself. So, what do I need to replace?

Sounds like a bad capacitor (at least you hope so). With all power off, go up on the roof, remove the cover and then access the "electrical area". Check capacitors for swelling, discoloration or leakage. Be sure to discharge by shorting terminals before removing. Any HVAC store should have capacitors to match.Could it be the compressor-- yes, but check the cheap stuff first!

How long does the back unit compressor stay off before restarting, as thermostats age sometimes they lose their differential settings. Another possibility is the area where the air blows out isn't sealed well from the air inlet where the filters are and the cold air is blowing on the thermostat capillary tube causing it to short cycle.and great answer Wolfe

Boy, Am I watching this with interest!!!! I have spent more than $1,500 with 6 different shops to try and solve the EXACT same problem. Nobody can figure it out!It happens with BOTH my A/C units. So, I think it is the generator misreading the spike and shutting itself off. But, two Onan repair facilities give my genny a clean bill of health.

There are many hard start kits available to reduce the amps at startupA 6.5kw should run both ac units

How large (small) is your genset? A 50 amp system would need at least a 6000K genset but since there is also a "surge" factor it might take 7-8K to simply break even. I have a 15K genset on board and have never encountered a similar issue but I certainly can see where this could be an issue.

Roottop AC | Good Sam Community

time_to_go_now
Explorer
Aug 30, 2015
Boy, Am I watching this with interest!!!! I have spent more than $1,500 with 6 different shops to try and solve the EXACT same problem. Nobody can figure it out!

It happens with BOTH my A/C units. So, I think it is the generator misreading the spike and shutting itself off. But, two Onan repair facilities give my genny a clean bill of health.
jyrostng
Explorer
Aug 30, 2015
How long does the back unit compressor stay off before restarting, as thermostats age sometimes they lose their differential settings. Another possibility is the area where the air blows out isn't sealed well from the air inlet where the filters are and the cold air is blowing on the thermostat capillary tube causing it to short cycle.

and great answer Wolfe
wolfe10
Explorer
Aug 30, 2015
Sounds like a bad capacitor (at least you hope so). With all power off, go up on the roof, remove the cover and then access the "electrical area". Check capacitors for swelling, discoloration or leakage. Be sure to discharge by shorting terminals before removing. Any HVAC store should have capacitors to match.

Could it be the compressor-- yes, but check the cheap stuff first!

Forum Discussion

Roottop AC

About Motorhome Group

Related Content

AC Clutch

ac unit

Rooftop ac repair

AC problem

Basement ac