Went to do a monthly exercise of the generator. After warm-up, I tried to turn the AC on for a load but it wouldn’t start. I could hear the generator slow down as the AC tried to start, and inside I can feel the AC unit vibrating as if it wants to start but no success. On top, I can hear the unit humming so it’s getting power. How should I proceed? Thanks!
If it were mine, I would first plug it into good power source from the house electrical and see if it'll start. If it starts at least you know it's not the air conditioner. If it doesn't start, check all the electrical connections in the converter panel especially the A/C breaker and at the A/C connection. All looks good there then go onto the roof and pull the shroud and check connections in the unit's control box. Look at the capacitor connections make sure nothing is burnt. Look at the run capacitor is it swollen does the fan motor run? Has it been a while since it last ran did it act up then? Lastly or first, don't cycle it on or off too quickly. Give it time to equalize pressures before you try to restart.
Jon
If it were mine, I would first plug it into good power source from the house electrical and see if it'll start. If it starts at least you know it's not the air conditioner. If it doesn't start, check all the electrical connections in the converter panel especially the A/C breaker and at the A/C connection. All looks good there then go onto the roof and pull the shroud and check connections in the unit's control box. Look at the capacitor connections make sure nothing is burnt. Look at the run capacitor is it swollen does the fan motor run? Has it been a while since it last ran did it act up then? Lastly or first, don't cycle it on or off to quickly. Give it time to equalize pressures before you try to restart.
Jon
Isn't the AC hardwired into the system or does it use a regular plug? Just wondering how you would plug it into another power source in the house portion of the RV?
Isn't the AC hardwired into the system or does it use a regular plug? Just wondering how you would plug it into another power source in the house portion of the RV?
What Jon S is saying is to plug the rig (not the AC itself) into shore power and then try to start the AC. If it fails to go, then it’s likely a problem with the AC unit. If so, I would guess a failed start capacitor. BTDT. — Jon
What the other Jon said.
Jon
Jon and Jon, I will try that next, thanks! This is the first time it has failed to start.
Greg, low voltage is a killer on any 110 volt refrigeration system. If you could check the incoming voltage when the A/C tries to start it would tell you allot.
Jon
What Jon S is saying is to plug the rig (not the AC itself) into shore power and then try to start the AC. If it fails to go, then it’s likely a problem with the AC unit. If so, I would guess a failed start capacitor. BTDT. — Jon
Ahhhhhh gotcha.
Greg, low voltage is a killer on any 110 volt refrigeration system. If you could check the incoming voltage when the A/C tries to start it would tell you allot.
How would I do that Jon?
After low voltage blew out our LD's A/C starting capacitor three summers ago and burned a terminal off the A/C's control switch two years ago, last summer I installed a soft-start device on the A/C. It eliminates the large startup surge and allows the A/C to start with low line voltage. No problems since.
Home - SoftStartRV (https://www.softstartrv.com)
We discovered an extra benefit on our late spring trip this year. On hot nights when sleeping with the A/C on, the banging or bumping that occurs when the compressor starts up is reduced or eliminated. When the A/C's compressor now starts, the soft-start ramps the power up relatively slowly, producing less noise.
It's a good upgrade if you camp where only a 15-amp plug is provided and the A/C is needed.
Larry
Thanks, Larry. That’s one of the upgrades I’ve been thinking about (along with the Fridge Defend product). Was the Softstart pretty straightforward to install? Which Softstart version did you get?
I used a SoftStartRV
SoftStartRV, The Amazing SoftStarter for RV A/C's – SoftStartUSA (https://shop.softstartrv.com/products/softstartrv)
I didn't find the wiring to be difficult but I have done electrical projects for the last six decades.
It does require finding the correct wiring diagram from SoftStart's website and applying it to the wiring inside the A/C's plastic roof cover.
As an example, this is the wiring instructions for a Dometic Duo-Therm A/C.
https://www.softstartrv.com/wp-content/uploads/2021/07/Softstart-Dometic-Duo-Therm-Straight-AC-NO-CUT-Install.pdf
Yoiur A/C is probably a different brand or model and may be wired differently, find the correct schematic here.
Dometic Wiring Diagrams and Instructions Identify Your Model - SoftStartRV (https://www.softstartrv.com/dometic-diagrams/)
Larry
OK, just ordered, $319 and free shipping. Thanks!
Going to move the RV next to the house this morning and investigate while plugged in so will report back later.
If it were mine, I would first plug it into good power source from the house electrical and see if it'll start. If it starts at least you know it's not the air conditioner. If it doesn't start, check all the electrical connections in the converter panel especially the A/C breaker and at the A/C connection. All looks good there then go onto the roof and pull the shroud and check connections in the unit's control box. Look at the capacitor connections make sure nothing is burnt. Look at the run capacitor is it swollen does the fan motor run? Has it been a while since it last ran did it act up then? Lastly or first, don't cycle it on or off too quickly. Give it time to equalize pressures before you try to restart.
Ok, it would not start on house electrical. Incoming voltage is good @ 122V. I checked all the AC connections in the converter and they are tight. Same symptoms as before. Hums and vibrates like it wants to start.
I took the shroud off and nothing jumped out at me. Where is the control box?
I found the control board underneath a sheetmetal cover. I blew everything out with compressed air and inspected it and didn’t see any loose connections, nor see or smell anything burnt. I’m assuming the big silver cylinder is the capacitor? If so, it doesn’t appear to be swollen. I tried starting the unit again with the sheetmetal cover off. The big black canister is getting very hot and the small one next to it is getting cold. Not sure if that’s from the sun beating down on it or something else. The humming seems to be coming from the large black canister.
Voltage at my Kill-a-Watt meter plugged into an outlet inside the coach drops from 122 to 115 volts while attempting to start.
Hi Greg; That 'large black canister' is the compressor. The AC voltage drops when the compressor is trying to run because it is drawing current and getting hot doing it. The silver cylinder is the starting (and running) capacitor. Quite likely it is bad. It shifts the phase of one pair of windings from the other pair that aren't shifted, to get the motor to turn. Hi heat can degrade these capacitors and they lose some efficiency. Age will do that also. They aren't very expensive and are easy to replace. That would be the first course of action to take. RonB
Thanks Ron. Would Dometic be the source for the capacitor?
Greg,
Type in V-000403 a bunch will pop up even amazon has them.
Jody
Dometic if you want to pay too much. Amazon is convenient. make sure the size is the same. Electrical value and physical. It need to fit in the same space. RonB
A word of caution: those big electrolytic capacitors store a LOT of juice, hold it for hours even after power is shut off, and release it instantaneously if the terminals are shorted. That can weld a tool to the contacts... or more important, it can kill a human. Be extremely careful when working with a big cap like that. Standard advice is to wear rubber gloves and keep one hand behind your back.
You can safely discharge a large capacitor, using a simple homemade capacitor discharge tool (https://www.ifixit.com/Guide/Constructing+a+Capacitor+Discharge+Tool/2177). This bleeds off the voltage at a safe rate through a large resistor. This video (https://www.digikey.com/en/blog/how-to-safely-discharge-a-capacitor) has more information. Please be careful when working on these units!
Just wondering, are the fans working? Like if you turn it on just fan mode, is it working? i didn't see any mention about it (maybe missed it) but after you mentioned that some parts are getting cool, maybe the a/c part is working but just not the fans...
No, the fan doesn’t blow either. From the inside, the unit vibrates and hums while trying to start.
interesting!! now I'm not very familiar with our ac units, but kinda sounds to me like it's the fan part that's having issues... not sure what kicks it off though, but hopefully with this info someone could chime in with something else to check further
Snip>>
The big black canister is getting very hot and the small one next to it is getting cold......... The humming seems to be coming from the large black canister.
Snip>> No, the fan doesn’t blow either. From the inside, the unit vibrates and hums while trying to start.
OK. I'm about 90% sure that what you have is a dead fan motor (and by dead I mean not running... it could have a start capacitor on it that could be bad, but I don't remember if those motors have start capacitors... it could also be a bad connection to the fan motor, or the windings could be bad/open), but that is all. I would not try running the unit any more at this time. The two statements above indicate that the compressor is working just fine. (Compressors get hot because they are compressing the gas, ie adding energy to the gas.) You (or a good repair facility) should be able to replace the fan motor relatively easily. Continuing to experiment will just shorten the life of the compressor. I really think this is a fixable problem.
Good luck.
Ken
Snip>>
The big black canister is getting very hot and the small one next to it is getting cold......... The humming seems to be coming from the large black canister.
Snip>> No, the fan doesn’t blow either. From the inside, the unit vibrates and hums while trying to start.
OK. I'm about 90% sure that what you have is a dead fan motor (and by dead I mean not running...
This should be easy to check - you should have a 'fan only' mode. If that does not work, then start with the fan as the problem. Try to turn the shaft with the unit off - if it is sticky to turn - does not spin easily - then lube has dried out in the bearings. Try a drop of 3-1 oil every place a shaft turns in a bearing, and work it until the shaft loosens.
Steve
Ok Greg, the big black thing is the compressor and they run very hot, burn your hand hot. The clue here is the small accumulator to the side of the compressor the copper line from it to the compressor appears to be frosted. If it is, then you need to get to the bottom of no fan motor. As Steve said, does it turn freely. If yes, is the motor itself very hot to the touch? If it's hot then you still may have a run capacitor issue if there is a separate capacitor or it might be the selector switch ( low, med, high ) If it's the selector switch the motor will not be hot and it should turn free. Your fan motor is critical as it is the indoor blower motor and the condenser fan so you need that motor to run.
Jon
According to the wiring diagram in your post 13 you have a run capacitor that has two separate capacitors in one. One side for the compressor the other side for the fan, center is common. If everything checks out it's almost pointing to the control board.
Jon
I think Jon and Steve have given you some great advice. When I read you post that I responded to yesterday, I was in something of a hurry, but mainly wanted you to know that it was not doing your compressor any good to continue to run it when the fan motor was not running. Replacing the capacitor is easy. Oiling the motor could be easy if it has the oil ports on the motor housing. It seems like the industry trend has been to permanently sealed motor lately. BUT, even if he motor is sealed, it should be replaceable. That would be cheaper than a new A/C unit. I don't remember how old your unit is, but if its fairly recent, I would most likely replace the motor if that turns out to be the problem. As Jon implied, further diagnosis depends on getting the fan motor running. And I hope I'm guessing correctly...getting the fan motor running will be the "fix".
Ken
As an afterthought, I seem to remember ( which is really dangerous, so proceed with caution) that removing the interior shroud exposed the squirrel cage fan, which is on the shaft of the motor in question. BE SURE TO REMOVE ALL 120 VOLT POWER. Then remove the interior shroud. You should be able to easily spin the cage and it remain going around. If it is at all difficult to spin or doesn't continue to spin, the bearings on the motor may be keeping it from running. Then you could could go up on the roof and see if the motor has oil ports. Just a thought.
Greg; At the age of rig, the fan motor shouldn't be seized up. Since this rig came from Florida, I suspect it ran a lot due to heat and humidity there. Along with high temperatures. The most likely failure is the starting capacitor for the fan blower. It is inside the same housing as the starting capacitor for the compressor motor, a double unit. If the blower fan blades turn easily, replace the double cap unit.
Flip off the circuit breaker in the distribution panel. Unplug shore power, (and no generator). There is usually a 'bleeder' built in for safety, and they both are likely connected to motor windings that will dissipate any charge. After a few minutes, I'd use a screwdriver shaft to temporarily short each terminal to ground (to ensure safety). There should be no spark.
These caps do go bad. That's why both are in the same unit. (might as well replace both. If one failed the other might be near failure). So likely there are pull off terminals. Mark them as to which terminal went where. Remove them and remove the capacitor. Now you can try testing it, or just replace it anyway. Testing isn't hard, but maybe for advanced meter users. Hope this helped Greg. Don't fall off of the roof! RonB
Greg, like Ron said you may have a failed run capacitor. In your case the capacitor for the fan and the compressor are in one. A dual capacitor if you will. Usually if a run capacitor fails the motor will not start and it'll cycle on it's internal overload that's why you need to feel the motor and see if it is hot. If it is hot and turns free definitely replace the run capacitor. If it is cool to the touch and turns free, look at where the motor gets it's power. I think you will find it comes off the solid state control board.
Jon
Thanks for everyone's input! The squirrel cage fan is accessible from the roof and turns easily. Is there another fan inside the coach?
I measured the physical dimensions of the large capacitor as Ron suggested (2 1/8" diameter by 4 1/8" long). There are three groupings of terminals on the top of the cap (5, 3, and 2). Is that because it's a dual cap? I'll be doing some research today and order the new cap.
If I fall off the roof (or fry myself discharging the cap) and survive, I figure it will only make me stronger! :D
So looking at Amazon, I'm not able to exactly match my capacitor. I was searching for 55/15 uF (which is a measure of capacitance, according to Google). Does the replacement need to be an exact match? Here is a photo of the existing cap:
Hi Greg; A match in size and shape since it is probably a tight fit. The capacitance can be larger, since heat exposure and age cause the values to decrease. A little overkill is good. You'll notice that tolerances for these caps are commonly like -10%, +40%. It's worth a try. RonB
The capacitance can be larger, since heat exposure and age cause the values to decrease. A little overkill is good. You'll notice that tolerances for these caps are commonly like -10%, +40%. It's worth a try. RonB
Thanks Ron. So a larger number is higher capacitance, ie, 60 is better than 55?
Use a little caution on the MFd try to find something pretty darn close the other thing is you voltage is 370. So not only MFG ( Micro ferit) but also voltage. I think the MFd needs to be close and the voltage can be within +-10%. That part of my HVAC back ground is gone. You will be lucky to find another round one, a lot are oval which totally upsets the applecart but you can make it fit with a little effort. Do you have a local HVAC shop they probably have one on their shelf.
Jon
Just to clarify, capacitance is most often measured in microfarads, abbreviated µF (Greek letter mu followed by capital F), but also sometimes written as mfd or uF.
Looking at Greg's photo, what he has there is labeled "55 / 15 µF ± 5% 370 VAC." So he needs a dual capacitor with at least 55 microfarads + 15 microfarads that can handle at least 370 volts AC. Larger values would be OK, but of course the replacement needs to physically fit in the space. As Jon pointed out, checking with a local HVAC shop may be your best bet.
Greg,
We ran into AC problems a couple years ago.
Replacing capacitor didn’t fix it but that is an inexpensive thing to try.
Turned out we needed a new motor. Was a fairly easy replacement.
Been working great since we did that.
Here is our thread when we had the problem.
Unusual Air Conditioner issue (https://www.lazydazeowners.com/index.php?topic=35269.msg219393#msg219393)
Thanks, I’ll check it out! Still trying to locate a capacitor.
Greg,
Search for a CAP-55/15/440R capacitor. They seem to be available from a number of vendors. There is also a 60/15 version that should work if it close enough in size. I finally replaced the start capacitor in one of our Mach-8 ACs and that fixed our start surge current problem and it now runs as it should.
Art
Greg, any electrical supply house should have one or an equivalent one - they just need a picture of the info on it.
The biggest problem I’m having is finding one with the same physical dimensions. The existing one is pretty tight so I can’t go any larger. I’ll try contacting a supplier. Thanks!
For those interested in the Soft Start products:
https://www.youtube.com/watch?v=Q_oVmsKOFTA&t=6s
Tagging onto this thread. I too have an A/C issue which I posted about. I think I'll just throw a couple parts at mine. I want to replace the run and start capacitors and the thermistor. I think I found the correct start but I'm confused about the appropriate run.
A few days back Jody posted:
Greg, Type in V-000403 a bunch will pop up even amazon has them.
That number brings up this one on Amazon: Run (https://www.amazon.com/TOMORAL-Capacitor-Condenser-Straight-Conditioner/dp/B099K1Z8SH/ref=sr_1_3?crid=2O0CPN3DLC6F7&keywords=capacitor+V-000403&qid=1658178094&sprefix=capacitor+v-000403%2Caps%2C239&sr=8-3). This one indicates 60/5 uF. Mine, however, shows 60+12.5 uF. I'm out of my area on this. Do I need to get one that specifically notes 60+12.5 uF? Thanks.
jor
Jor, I recommend you measure the physical size as well. If yours is like mine, it’s pretty tight where it mounts. Mine is a dual capacitor.
I am learning a lot about capacitors and such thanks to YouTube. Found these two videos and was able to safely remove it (using the screwdriver method-there was no charge on it). Tested the old capacitor and both sides are bad. Physically, it looks fine other than a little corrosion on top. Next step is to find a suitable replacement and reinstall it. I took lots of photos of the wire connections so hopefully will connect the new one properly!
https://www.youtube.com/watch?v=19A9lvQ6lIA
https://www.youtube.com/watch?v=PBoOx8YzD_s
So I found this capacitor which is only slighter physically larger but may fit. This is a 55/10 vs. the original which is 55/15. Would the difference be a problem?
GE Genteq Capacitor Round 55/10 uf 370 volt Z97F9974 97F9974 | eBay (https://www.ebay.com/itm/271849136669)
So I found this capacitor which is only slighter physically larger but may fit. This is a 55/10 vs. the original which is 55/15. Would the difference be a problem?
GE Genteq Capacitor Round 55/10 uf 370 volt Z97F9974 97F9974 | eBay (https://www.ebay.com/itm/271849136669)
It has been a LOOONG time since I had an AC motors course in college, so things are pretty rusty!
My concern is that the 15 uf run capacitor was probably chosen to balance the inductive load of the compressor motor to maximize something called the "power factor". Using a 10 uf replacement could cause the motor to run slightly less efficiently and thus slightly hotter. The start capacitor is likely less critical, since it is just involved in helping the motor spin up to speed. It might be good to find a shop that fixes electric motors to get their opinion.
Art
Thanks for that, Art. I ended up purchasing this capacitor from Amazon. The specs should be good and physically it's only slightly larger so hopefully I can mount it in the same place.
CBB65B Run Dual Capacitor 370VAC 370V AC 60/15uF 60+15uF 60MFD+15MFD... (https://www.amazon.com/dp/B086SXQ4JQ?psc=1&ref=ppx_yo2ov_dt_b_product_details)
Glad you stayed within specs. Sometimes they are a little harder to mount but if there is a will, there is a way.
Jon
Following up on this thread. Looks like the new capacitor fixed the problem! Had no problem physically fitting the new one in as it was only slightly longer and the same diameter. Currently testing the system but everything is looking good so far!
It might be a good idea to buy a spare capacitor for future use
Job well done Greg!
Thanks, Art! Initially the Heat Pump mode wasn't working (AC only) but when I reset the Dometic thermostat it started working.
Now I can tackle the SoftStartRV unit!
It might be a good idea to buy a spare capacitor for future use
Adding a soft-start device will eliminate the start-up surges that can damage the starting capacitor.
With our summertime power problems, low voltage is expected in the afternoons on scorching, causing hard starts.
Larry