Do I need a hard start kit?

[87Itasca]

Hi all,

On my front Delta TX roof AC, I've had a problem since the fan motor locked up and it ran for an unknown amount of hours with no airflow over the condenser.  The issue is that the unit will come on after I push the switch, try to engage the compressor, fail, then toggle the 'Low Power' LED. After a minute, it will try again and again every minute until I either shut it off (give up) or until it finally works.

I checked with my meter today, and I have 121.3V at the receptacle the unit is plugged into. The voltage is the same inside the coach with nothing running. The receptacle is a 15A adapter plugged into a 20A circuit, hooked up to a 30' 30A extension cord, plugged into the shore cord. A little sketchy I know, but it's the best I have where I keep it parked.

When I turn on the AC, I measure 119.3V with the fan on. When it tries to engage the compressor, I drop to 82/83V at the control box, then the low power light cones on, and the voltage goes back to 119.3V.

When the compressor does kick on finally, it only drops to about 85V, then goes up to 107V throughout the coach as long as the compressor runs. When the compressor cycles off, I'm back to 119.3.

On the rear (trouble-free) AC unit, when the compressor engages, the voltage drops to 89-90V, and the voltage through the coach is 115V while the fan and compressor are running.

Clearly, the front unit is drawing more power than the rear unit. Would a hard start kit like the SPP6 give me a little more life and ease the extra load on the front unit, or am I out of luck?

[Rickf1985]

There is your problem, You are not supplying enough power to the unit! You have to have the RV plugged into a 30 circuit or the AC will NOT work. I hate to say it but you may have damaged it from trying so long with such low voltage. Mine will not come on plugged into a 20 amp circuit through an adapter either but it works just fine on the generator or plugged into a 30 amp circuit.

[M & J]

A hard start kit will like probably extend the life of the compressor, the wall units I have put those on ultimately have failed. Rick is correct in you are overloading your shore power but the fact the rear unit runs without drawing down the AC and the front unit when running  does tells me it's a compressor working hard to do its job.

[87Itasca]

I don't know if it's a power issue honestly. We're that the case, both units should have the same problem. The rear one has never acted up, and draws down the voltage from 119V to 115V as its running. The front unit, acting alone, should act identically, but it does not.

[Rickf1985]

Have you checked all of the connections from the AC back to the box? And I mean ALL of them? You probably should do a voltage drop test to see if the power is dropping just at the unit or if it is dropping at the incoming line also. With a good line it should never drop to 85 volts, it should stay at 110 volts and blow a breaker. Something is wrong in the wiring.

[DaveVA78Chieftain]

It is the excessive cable length that is creating the problem.  Voltage dropping to 85-90 VAC is basically a brownout that can damage motors. 

[87Itasca]

I will try it out this weekend at the campsite and see how it does. It just seemed a little coincidental to me that it did this after the fan motor went out and it kept running.

I wish I had a 30A service at the shop to hook it to, but I do not. If everything works properly this weekend, I'll know its most likely the adapter.

I will do a voltage drop pinpoint this week before I leave if I get the opportunity, otherwise I'll be the first of this coming week. Thank you guys.