A/C Won't start

[BurbMan]

Plugged into 20A shore power in buddy's driveway. Running a 25' #10 30A RV extension cord in addition to 25' shore power cord. I've run the a/c in this location before, but no go this week. The a/c buzzed but never started, so I turned it off after about 10 seconds. The breaker is fine, the fan runs, but now turning on a/c does nothing...no noise, no buzz, nothing.

The unit is a 15k rooftop ducted a/c, not sure what brand. From what I have read it sounds like the capacitor is gone, but not sure how to check it. Also, how do you discharge a capacitor so it can be changed safely?

Any other ideas?

[Golden_HVAC]

You can buy a clamp on amp meter from Lowes for $40 that will measure capacitance. For a little more, $80 you can get one that also measures DC amperage by clamping the meter over a wire. Both will also measure the motor to ground up to 20 Meg ohms, and measure temperature too!

I have tested many capacitors, and it has saved me from replacing 3 motors within the past 3 months.

Good luck,

Fred.

[j-d]

The two RUN capacitors shown above might be combined in one "can" but function's still the same. If the power is OFF, the capacitor(s) will probably discharge, but you can (again Power Off) take an insulated tool like a screwdriver with a plastic handle and short their terminals. Then you can handle them.

If cap looks damaged, you know it's bad. Otherwise, some meters will test them, or replace with a known good one.

Your A/C may or may not have the start assist device. If you want to add one, the SUPCO SPP6e is recommeded. It's a smart device, not the simple PTCR type.

[Golden_HVAC]

Golden_HVAC wrote:
Here is a picture of the popped capacitor and the good one on the right.



Fred.

Here is another post that I made, with a picture of the larger compressor capacitor and the smaller fan capacitor.

The picture above, the capacitor actually exploded, while most failures they might look like normal, or look like the top has 'popped up' as shown in the picture on the left, while I have never (in 31 years) seen one where the 'can' part of the capacitor ever came apart.

Golden_HVAC wrote:

Golden_HVAC wrote:

RoyB wrote:
Here is a neat article from google search with some photos...

HARD START CAPACITOR FOR RV A/C

Roy Ken

If you where to click on the link above, you will see several pictures, including the removal of the 4 screws to open the top of the A/C unit on your roof.

Here is a picture of the two capacitors. The smaller silver one is attached to the indoor fan motor.



The larger silver capacitor is the run capacitor for the compressor.

Good luck,

Fred.

Remove the top of the outside unit, and you should see both of the capacitors in there, looking like the picture above this one. If one has popped, then shut off the A/C for this weekend (at the circuit breaker) and Tuesday they should have them at a place like Grainger or Johnstone supply, or most any electrical supplier. Many will not sell to retail buyers, but if you are wearing a company shirt, they will take your cash, if you tell them your personal A/C quit.

I have not seen the capacitors at a place like Home Depot. It is more a motor supply place, or my local HVAC supplier.

Fred.

[wolfe10]

What is the voltage BEFORE and DURING A/C start up?

[2oldman]

Hmm.. in the past has the voltage been sufficient with this same setup?

[BurbMan]

No, nothing else on except the converter, but TT has been plugged in a while so batteries are charged and 12v draw minimal.

[2oldman]

Yes, something else is on, like water heater or converter.