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bigben2020 06-16-2021 06:27 PM

Please help - A/C not working
 
Wife and daughter were dry camping at Onion Valley in Eastern Sierra in our new AI 24GT. Yesterday they watched TV for hours with inverter on and did not monitor battery (lithium). They did switched off the inverter. This morning they noticed the voltage of house battery was ~10. After driving for hours to another campground, the battery is now back to over 13v. And solar is working fine also. However, when she switched on generator in order to use A/C just now, the start of A/C would immediately shut off both generator and A/C. The only other appliance that's affected is the ceiling fan in the bathroom that stopped working this morning. What happened?
Thanks for any suggestions!
Jeff

uncle_bob 06-16-2021 06:39 PM

Quote:

Originally Posted by bigben2020 (Post 2506053)
Wife and daughter were dry camping at Onion Valley in Eastern Sierra in our new AI 24GT. Yesterday they watched TV for hours with inverter on and did not monitor battery (lithium). They did switched off the inverter. This morning they noticed the voltage of house battery was ~10. After driving for hours to another campground, the battery is now back to over 13v. And solar is working fine also. However, when she switched on generator in order to use A/C just now, the start of A/C would immediately shut off both generator and A/C. The only other appliance that's affected is the ceiling fan in the bathroom that stopped working this morning. What happened?
Thanks for any suggestions!
Jeff

Hi

Looking at battery voltage under load is always in iffy sort of thing. Current flowing through the wiring can easily throw measurements off. That said, let's take the readings as being correct ( .... it's what we have ... ).

10V on lithium batteries is right at the "lights out" point. You have run them flat. Don't do that ... :)

13V is (at best) half charged on lithiums. Your hybrid inverter/charger will be going a bit nuts (if the generator is running). The same would be true of the DC/DC attached to your alternator if the engine is running.

A/C units have a pretty big surge at start up. Combine this with the charger going full bore to fill the batteries .... you have a big draw on the generator. Best guess ( and it's only a guess ) is that the generator was overloaded and shut down.

Complicating all this is the recall that's out for the 12V side of a lot of Interstates (yours may be one of them). There may be other issues (like trip points being set wrong) .....

Bob

Heckler56 06-16-2021 06:51 PM

Bob said it best. You can only run the AC with the generator and no other appliances. If your batteries were still low, then the charger likely turned on and that was too much with the AC.

Make sure whenever using the generator to run it without anything on particularly the AC for 3-5 minutes. Before turning on the AC spend the 3-5mins looking around to see if the charger is running or micro or frig, etc.

carl2591 06-16-2021 07:07 PM

get the Micro Air soft start kit for the ac as well.. the LRA (locked rotor amps) on them runs like 50 amp or more.. the soft start reduces that down to 20 or so.. easier on the genny as well..

https://www.micro-air.com/products_e...r_microair.cfm

they are on amazon as well OF COURSE.. LOl..

bigben2020 06-16-2021 07:24 PM

DW just said it's 13.1v, so it's like ~40% full. That makes sense!

bigben2020 06-16-2021 07:53 PM

Quote:

Originally Posted by uncle_bob (Post 2506065)
Hi



Looking at battery voltage under load is always in iffy sort of thing. Current flowing through the wiring can easily throw measurements off. That said, let's take the readings as being correct ( .... it's what we have ... ).



10V on lithium batteries is right at the "lights out" point. You have run them flat. Don't do that ... :)



13V is (at best) half charged on lithiums. Your hybrid inverter/charger will be going a bit nuts (if the generator is running). The same would be true of the DC/DC attached to your alternator if the engine is running.



A/C units have a pretty big surge at start up. Combine this with the charger going full bore to fill the batteries .... you have a big draw on the generator. Best guess ( and it's only a guess ) is that the generator was overloaded and shut down.



Complicating all this is the recall that's out for the 12V side of a lot of Interstates (yours may be one of them). There may be other issues (like trip points being set wrong) .....



Bob

Thanks very much Bob. I'm usually pretty careful about the battery state. But this TV on 110 is really new to us. We had a Forester that came with a TV on 12v. I really want to replace the current TV with a smart tv on 12v.

Boxster1971 06-16-2021 09:10 PM

Quote:

Originally Posted by bigben2020 (Post 2506086)
. . . But this TV on 110 is really new to us. We had a Forester that came with a TV on 12v. I really want to replace the current TV with a smart tv on 12v.

You have identified the most idiotic part of the Interstate electrical system. Airstream installs a 1,000W inverter to power the TV and no other onboard systems. It's just crazy.

I installed a 12VDC TV years ago in my Interstate and it works great.

bigben2020 06-17-2021 06:58 AM

Quote:

Originally Posted by Boxster1971 (Post 2506099)
You have identified the most idiotic part of the Interstate electrical system. Airstream installs a 1,000W inverter to power the TV and no other onboard systems. It's just crazy.

I installed a 12VDC TV years ago in my Interstate and it works great.

Mike, what model did you get and how did you wire for the TV?

Foiled Again 06-17-2021 07:52 AM

Of course one CAN plug a 120 volt television into an inverter circuit and run it on 12 volt (inverter on), but whatever 12 volt it draws is also increased by the inverter itself. I have standard lead acid batteries and can still go a week without hookups - with only a Honda 1000.
But that requires super careful management (like using the generator to recharge the batteries at least one time,) and cooking with propane or charcoal, and keeping the fridge on propane.

I have been in a winter campground when a snowstorm took out power for.almost 10 days. Long drive to Tractor Supply kept me in propane, and I had to buy 5 gallon gas refill tank to keep tiny genny running, but campers are generous people and everyone who had a generator went around the camp charging other campers' batteries. The convoys to three propane refillers in the area were pretty interesting too. (Apparently showing up with 18 or so empty tanks in the bed of a pickup isn't totally kosher?)

uncle_bob 06-17-2021 08:13 AM

Quote:

Originally Posted by Boxster1971 (Post 2506099)
You have identified the most idiotic part of the Interstate electrical system. Airstream installs a 1,000W inverter to power the TV and no other onboard systems. It's just crazy.

I installed a 12VDC TV years ago in my Interstate and it works great.

Hi

The inverter also powers the electric coffee grinder in the morning :) :)

.... errrr .... where's that "convenient" outlet to plug it in .... hmmm ..... need to plug the TV back in after I'm done ... .:)

Bob

Boxster1971 06-17-2021 08:23 PM

Quote:

Originally Posted by bigben2020 (Post 2506169)
Mike, what model did you get and how did you wire for the TV?

I installed a Jensen 19" 12VDC TV with DVD player in the rear mount near the lounge bed. I added 12VDC / USB outlets on both sides near the rear windows when I rebuilt the entire electrical system in 2014. Now have 400W solar, 440AH AGM batteries and a 2,000W inverter/charger that allows me to run microwave off batteries.

This is the TV I installed. There are also 12VDC smart TVs available now.
https://www.amazon.com/ASA-Jensen-JT...dp/B01MZZH8R1/

uncle_bob 06-18-2021 08:51 AM

Hi

A lot of small tv's come with an external power supply. It takes 120V in and shoves a DC voltage out to power the TV. They all are marked with a voltage and current. I have never seen one on a TV or monitor that was much over 22V (though they could be out there).

One somewhat bold option would be to get a nice efficient (adjustable) DC/DC converter and rig it to drive the TV. With some luck shopping, you should be able to find one that is in the vicinity of 90% efficiency and only pulls 10's of ma when idle. Yes, this is getting deep into electronic DIY.

Folks also use this DC/DC approach with their 24V CPAP machines. It seems to work a lot better than running them off the inverter.

Bob

bigben2020 06-20-2021 08:59 AM

Update on the problem and tests -
Just as suggested by experts here, the low battery charge was the cause for the A/C issue. Once the battery was charged to ~13.5v, the A/C ran fine on generator without tripping the system. So did microwave.
So, to figure out how this happened, I tried to reproduce the problem and monitor the voltage closely. I started at noon when solar was charging around 11A and battery was at 13.5v. I kept the unit unplugged from shore power. The inverter was on, TV was on and playing non-stop. Refrigerator was on as well. No other major appliances were on. Almost immediately, battery read 13.2v but never dropped below 13.1v in the next six hours! So that was a surprise. Or not really surprising as I discovered that the TV (Connexx LED CX24A20) draws 0.4A at 110v, equivalent to 3.7A at 12v, and fridge 3.5A at 12v, so combined at no more than 8A at 12V. Therefore the two 100 Ah batteries even at 50% charge should be able to handle the two appliances for at least 12 hours before drained to zero.
So, am I missing something?
DW mentioned that the fridge made constant louder noise throughout the night as if it worked overload. They camped at over 9,000 ft elevation, would this be an issue to the 12v fridge? I had experience with propane fridge at high elevation but have no idea if this could happen to an electric one. Perhaps refrigerant does not work optimally at lower pressure? But it's a closed system.
Questions, more questions..

casebor 06-20-2021 03:23 PM

Micro Air soft start kit
 
Does Micro Air soft start kit void any warranties?
what's involved with regards to the install?
Thank you in advance

uncle_bob 06-20-2021 04:14 PM

Quote:

Originally Posted by casebor (Post 2507362)
Does Micro Air soft start kit void any warranties?
what's involved with regards to the install?
Thank you in advance

Hi

Warranties: You would have to check with the manufacturer of your specific A/C unit. Best guess without specific info from them ... yup. Most of the soft start outfits supply a limited warranty of some sort. I'd read the details pretty carefully.

Install: There are some parts to put into the unit "up on the roof".

One of the very basic issues is that the compressor section of most RV A/C units is not cheap to repair. Indeed many places will tell you they are all non-repairable. (some are / some aren't). Spending more to replace a compressor than the cost of replacement is not the way most folks go when one breaks.

Bob

JonDNC 06-20-2021 05:41 PM

Quote:

Originally Posted by casebor (Post 2507362)
Does Micro Air soft start kit void any warranties?

what's involved with regards to the install?

Thank you in advance



Micro air does offer a 3 year warranty, it it obviously is limited in what it covers. I waited a year on our trailer before I installed 2.

Boxster1971 06-21-2021 10:11 AM

Since this thread has shifted to a discussion about Micro-Air EasyStart. . . .

I just removed the Micro-Air EasyStart kit from my Interstate. It has never worked right on generator power because the Precision Circuits Inc. Power Control System (PCS) in my coach is too sensitive in GEN mode and disrupts power to A/C unit as soon as current goes above 18A in GEN mode. Even with EasyStart the compressor start would exceed 18A and that tripped PCS which tripped EasyStart into a 5 minute shutdown. Then it would just repeat cycle and never run A/C compressor on generator.

Before installing EasyStart kit I could always get A/C to run on generator after disabling PCS by shutting off circuit breaker that supplies power to PCS. Generator can handle start surge without intervention from PCS. Thought EasyStart would reduce generator burden, but it just made it worse by getting into repeated protective shutoff cycling.

When first installing the EasyStart in 2019 I spent many hours troubleshooting and exchanging emails with Mirco-Air techs. They always blamed generator for my problems. I rented a Honda 2000W generator and plugged it into external shore power with PCS set to 20A service mode. It worked fine. That convinced me that PCS GEN mode was the issue.

Now that I'm preparing to start a long trip I renewed my troubleshooting of this issue.

First step was purchase of a new meter that could measure capacitance of start and run capacitors. They were all within spec. Removed the EasyStart and reinstalled the original start capacitor. Also rewired my Progressive EMS to monitor power from both shore and generator. This is helpful since I must disable PCS to get A/C to run on generator.

Now I can run the A/C again on generator with no problems. Sure there is a high current surge on compressor start, but generator handles it OK. Steady state A/C run current is now 18-19A, 2A for fan and 16-17A for compressor.

I think newer Interstates have an improved PCS that likely eliminates this issue.

uncle_bob 06-21-2021 10:50 AM

Hi

18 to 19A is a lot of current for an A/C ( Not to say it's broke ). Most folks these days seem to be around 14 to 16A (with the 16 being heat pump mode). The lower current drain may be helping the newer Interstates.

Bob

rowiebowie 06-21-2021 11:36 AM

Quote:

Originally Posted by uncle_bob (Post 2507609)
Hi

18 to 19A is a lot of current for an A/C ( Not to say it's broke ). Most folks these days seem to be around 14 to 16A (with the 16 being heat pump mode). The lower current drain may be helping the newer Interstates.

Bob


I agree that is very high amps. My old '2012 13.5k btu 'Coleman ran at 13-14 amps. My new larger Coleman 15K btu runs at 11-12 amps. A testament to increased efficiency of the newer units. All the above draws are based on "low" fan speed. Add one amp for high fan.

Some new Coleman NDQ units run below 10 amps.

Boxster1971 06-21-2021 01:29 PM

I agree that the 18-19A seems high. I've seen it drop to 16A occasionally while monitoring my EMS display. It was hot (90+) when I checked those values.

It is an older, 2012, Dometic Penguin II A/C. Purchased Interstate new in October 2012.

My A/C must be drawing more as it aged. When I first used the A/C on generator back in 2013 right after I bought it new it ran just fine with the PCS. A few years ago it started to act differently and I had to disable the PCS to run on generator as the compressor start current was apparently higher. That is why I got the EasyStart.

Since capacitors are all measuring in spec I can only conclude the compressor may not last much longer. Main goal now was to get it working on generator again in case I need it for our trip next month.


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