Community Forums

rsw1943 · 03-01-2014, 02:35 PM

I have a l997 Bounder with a Coleman AC unit on top. When I turned on the AC it used to start up in few minutes. This last year it would take about 10 minutes to start up. This month while exercising the generator I turned the AC on and it took 20 minutes to start up. Today I had the coach plugged in and turned on the AC and it would not start. Need help why it won't start.

al2ride · 03-01-2014, 04:48 PM

Freon leak? There is a sensor that will prevent it from starting if the pressure is below a certain amount.

GaryKD · 03-01-2014, 05:38 PM

Hi rsw1943,
In addition to what al2ride posted, the start and/or run capacitors could be going bad.

chboone · 03-02-2014, 09:25 AM

The Dometic AC's have a two minute timer build into the circuit board to keep it from starting when first powered on. Would assume Coleman would have the same, that part of your circuit may be going bad. If you have or can get the installation manual for your AC, you maybe able to play with the dip switches that control the timer, if that's what Coleman uses.

Chuck

gemini5362 · 03-02-2014, 10:03 AM

I think your start capacitor may have been going bad and is finally bad. That would be my first guess. The next guess is that you might have a bad compressor motor. In home A/c units over the years the compressor starts getting old and has trouble starting. Eventually it will not start and the fix for that is a booster starter cap. This will work for a while until finally it is new compressor time. Replace the cap first and see if that helps. Before you do any of this though find the 115 volt wires going to the motor itself. See if you have 115 volts on them when you turn the A/C on. If you do not have 115 volts after it has been on a couple of minutes start troubleshooting why not before doing anything.

chboone · 03-02-2014, 12:09 PM

Does the fan come on by it's self without the compressor after a few minutes? If the fan does not run without the compressor starting, I doubt it is a compressor or capacitor problem. If the capacitor is bad or weak and there is a problem with the compressor, you should hear the compressor trying to start. When the compressor is trying to start and can't it pulls high current, probably over 30 amps. That is well over the rating of the 20 amp breaker it's on and cause the breaker to trip. Do you here the hum of the compressor trying to start? I still think you have a control problem, be it with the thermostat or circuit board.

Chuck

rsw1943 · 03-02-2014, 12:41 PM

CHBOONE

Nothing tries to start. I can turn on the fan on manual and it runs just fine. No noise or hum from compressor. Not even a click.

Brez · 03-02-2014, 01:42 PM

Sounds like the cap lost its charge to start the compressor. Check around the AC unit and see if there's any fluid. Sometimes the cap may get punctured and slowly leak eventually failing that's why the odd operation. Or the Cap lost it dielectric strength.

Cat · 03-02-2014, 07:36 PM

Coleman has problems with the fan bearings binding. It will do exactly what you described. Mine got worse and worse, trying spinning the fan if it spins easily it's not the fan motor if it is stiff, replace it.

gemini5362 · 03-02-2014, 10:00 PM

Ok so the fan will work in manual. That means there is power getting up to the AC. It also means there is nothing wrong with the fan. You have several possible suggestions already. 1. The compressor start cap is bad. 2. The compressor is bad. 3 Something wrong with the thermostat circuitry. 4. Broken wire somewhere between the thermostat and the compressor. My earlier advice is still good get a meter and clip it onto the wires going to the compressor. See what voltate is n those wires when the thermostat is turned on. If you have voltage there then the next step is to replace the start cap. I do not believe those caps will be expensive and it will keep the compressor from starting. If you have 115 volts to the compressor and you have replaced the starting cap and the compressor is still not running I am going to believe you have a bad compressor.

chboone · 03-03-2014, 12:01 AM

Quote:

Originally Posted by rsw1943

When I turned on the AC it used to start up in few minutes. This last year it would take about 10 minutes to start up. This month while exercising the generator I turned the AC on and it took 20 minutes to start up. Today I had the coach plugged in and turned on the AC and it would not start.

Not saying it can't happen, in all my years of working on HVAC I've never seen a weak or bad capacitor delay starting a compressor 10 or 20 minutes. Do you recall when you first started have the delayed start problem, did you ever hear the compressor trying to start? While I don't think it is the problem replacing the run capacitor would be the cheapest part to buy. You can get it at any appliance store that sell parts. Take the old one with you so they can match the voltage and mfd (microfarad) charge ratings. Before you removing the capacitor turn off the AC breaker and discharge the capacitor by disconnecting the leads and shorting the capacitor terminals together using a insulated screwdriver or wire. Ask the store if they will test the capacitor for you, should do it for free.

Chuck

chboone · 03-03-2014, 03:35 PM

Let get into this a little further. If your going to do the work yourself, while on the roof you can do some other testing if you have a VOM. Here two examples for discharging and testing a capacitor.
How to Check a Start Capacitor: 8 Steps (with Pictures) - wikiHow
How to Discharge a Capacitor: 5 Steps (with Pictures) - wikiHow
If you don't feel comfortable doing it take the capacitor to an appliance repair store/shop. Make sure you don't touch the terminals with your bare hands, use insulated pliers to remove the wires from the capacitor. You can also test the motor windings and external overload (klixon) with the ohm meter. With the power off to the AC locate the terminal cover for the compressor, remove the cover. The easiest to test is the overload, which should be under the terminal cover. Remove all wires from the compressor, take a picture or mark the wires so you can put them back in the correct position when finished. With the VOM set for continuity testing or you can use the ohm scale connect to each of the terminals of the overload. You should get continuity or full scale reading if it good, if no reading it needs to be replaced. The compressor has three terminals C = Common, S = Start, R = Run and should be identified on the terminal cover. With the meter in the ohm scale set it at the 100 or 200 depending on your meter. Connect the meter probes to the C & S terminals, record the reading. Next connect to the C & R terminals, record the reading. Next connect to the S & R terminals, record the readings. Add the first two readings together, the third reading should be the total of those two. If it not close to that total or you don't get any reading there is a problem with the motor windings. However, with all that said I stll don't think problem with the start capacitor or a hard starting compressor because your are not tripping the breaker or hearing the compressor hum when trying to start. It's either a control problem, lose wiring, open overload, or open motor winding.

Chuck

gemini5362 · 03-04-2014, 09:19 PM

Quote:

Originally Posted by chboone

Let get into this a little further. If your going to do the work yourself, while on the roof you can do some other testing if you have a VOM. Here two examples for discharging and testing a capacitor.
How to Check a Start Capacitor: 8 Steps (with Pictures) - wikiHow
How to Discharge a Capacitor: 5 Steps (with Pictures) - wikiHow
If you don't feel comfortable doing it take the capacitor to an appliance repair store/shop. Make sure you don't touch the terminals with your bare hands, use insulated pliers to remove the wires from the capacitor. You can also test the motor windings and external overload (klixon) with the ohm meter. With the power off to the AC locate the terminal cover for the compressor, remove the cover. The easiest to test is the overload, which should be under the terminal cover. Remove all wires from the compressor, take a picture or mark the wires so you can put them back in the correct position when finished. With the VOM set for continuity testing or you can use the ohm scale connect to each of the terminals of the overload. You should get continuity or full scale reading if it good, if no reading it needs to be replaced. The compressor has three terminals C = Common, S = Start, R = Run and should be identified on the terminal cover. With the meter in the ohm scale set it at the 100 or 200 depending on your meter. Connect the meter probes to the C & S terminals, record the reading. Next connect to the C & R terminals, record the reading. Next connect to the S & R terminals, record the readings. Add the first two readings together, the third reading should be the total of those two. If it not close to that total or you don't get any reading there is a problem with the motor windings. However, with all that said I stll don't think problem with the start capacitor or a hard starting compressor because your are not tripping the breaker or hearing the compressor hum when trying to start. It's either a control problem, lose wiring, open overload, or open motor winding.

Chuck

Chuck this is very good advice I am going to deviate from it a little bit. First of all the link to checking the cap. It shows checking the cap with an analogue meter. This works as a rough check but if you are not experienced with this type of check might or might not be a realistic reading. It shows how to check with a digital meter. The input impedance for the analogue meter is in the kilo ohm range and you can see some deflection. The input impedance for the digital meter in the high megohms. You are attempting to charge the cap and then when you reverse leads you discharge and look for the meter reaction. The meter reaction is going to be a product of the capacitance x the input impedance of the meter. In short very hard to see with a digital meter unless you have a very expensive one and not easy then. The reality is caps are not very expensive and is easier if you are going to go to all of that trouble to just get the new one. Plug it in and see if your compressor starts.

Your advice about checking the windings is very good. If the OP is going to check anything at all with a meter they need to get on the roof get to where they can see the leads put a meter on them have someone turn on the thermostat wait a few minutes and see if they have any voltage there. That needs to be the very first thing to check. If they have voltage then do the checks you recommend. If they do not have voltage find out why. I agree with the advice to discharge the capacitor before you touch it I am going to ad to make sure the power is off to the air conditioner before you do that.

chboone · 03-04-2014, 10:25 PM

gemini,
Yes I agree about the differences of testing with an analog and digital, have used both. I prefer the analog for testing a cap. Most DIY'er are not going to spend the money for a good digital that will be capable of testing a cap. The reason I attached the web pages, it was easier then trying to explain the testing plus there were illustrations. As you say the start cap is inexpensive and would be the easiest for the OP to replace. However, I still don't think the start cap is the problem since the OP has never said he heard the hum from the compressor trying to start when he was experiencing the delayed starts. He should have at least heard the compressor try to start a couple of time on the overload during the 10 or 20 minute delay. Since the compressor will not run now, what ever component that was causing the delayed start has completely failed. If the OP is capable of performing some testing and checking he may find the problem, or take it somewhere to have it repaired. With that said, first and foremost, check if he is getting power to the compressor when it is call to run. Hopefully, he does report back what the problem is determined.

Chuck