Roof top AC

Makes sense. I am 30 amp and have the EMS. I've noticed that none of the green lights are on at the EMS when this issue occurs. When both are on I am pulling 20 amps on the EMS. When one unit is on it is 13 amps. I dont have a 30 amp supply at home, but maybe I can locate one somewhere to do the check. Thanks.

Gile wrote:
Just started using the RV this month. Both units run at the same time with no problem. Just takes about 30 minutes to kick in at first start.

Is there a reason you do not want to post the info needed to help you out?????? WITHOUT that info, NOBODY can help you at all. Doug

Some air conditioners are smarter than I am.. I have been known to turn one off and turn it right back on (This is very hard on the compressor) so the makers of SOME models include precision timers that insure that when the compressor stopps it is at least THREE minutes before it kicks back in.

IF this timer is defective... Well 30 minutes is possible.

A clamp on ammeter (I will tell you how to do this) can help diagnose.

How to use the meter

Method 1: Open breaker box and "Clamp" on the wire to the Air Conditioner.

Note the amprage (Should be zero) with the unit off
Turn it on Fan only, Note the reading

Turn it on to COOL note the reading,, (it should go way up then quickly go down to around 10-15 amps. and the compressor SHOULD be running.,

IF it goes up, then back down to 'Fan only" then up then back down to Fan Only.

Read the posts above mine.,

If it takes 30 minutes to go up.. This post.

NOTE: if you are on 50 amps and have an Energy Management System (Load Shedder) you must be on 50 amps to run this test.

Method 2 (works on 30 amp rigs) use a 30-50 and 5-30 dog bone adapters on the power cord, ONE of these has to be a "Flat" cable type (3 wires side by side) Separate out one of the outside wires and clamp on that. NOTE that with this method the amp readings will be higher (since you are also reading current to the TV, Fridge, Converter, Et-al)

Just started using the RV this month. Both units run at the same time with no problem. Just takes about 30 minutes to kick in at first start.

You just joined.
ALWAYS post Year/Brand/Model of RV
For technical questions like you asked, you need to post the Brand and Model number of the A/C unit and what type Tstat you have.
Simple answer is, the MAX it will take for ANY compressor start on a RV A/C unit is 3 minutes. The Start Capacitor and Run Capacitor will have no bearing on any type delay. As another poster stated, IF you have a EMS system(energy management system) that monitors your 120 voltage, That may cause a delay, but you will have a panel inside that will show you the status of that system. Doug

I don't know what it's called but some RVs have what I'll call a "Load Shedder" that doesn't allow both rooftop A/C to run at once. Switches between them. That sounds to me like a feature that could go haywire.

Gile wrote:
I assume the start capacitor is in the roof top unit? Both units are doing the same thing.

Oh, important detail! Yes, the capacitors are in the unit up top, so that is not your problem if both are doing the same thing. The thermostat is more likely the cause. Odd one, though. Did your originally have a 2 minute delay before the units would cut on? That is what mine does. If so, maybe that "feature" has gone haywire.

I assume the start capacitor is in the roof top unit? Both units are doing the same thing.

Sounds like it could be the start capacitor. I recently had the opposite - compressor would start but not the fan. If I helped the fan, it would start. Replaced both capacitors while I was at it and good as new. You might not want to continue using it like that or you might burn out the compressor. Others might have a more definitive statement on that, but it would make me worry.