Open Roads Forum

Print  |  Close

Topic: my roof ac unit will not work while driving

Posted By: zorro1421 on 08/19/11 12:33pm

CAN ANYONE HELP ME FIGURE OUT WHY MY ROOF A/C WILL NOT OPPERATE WILL DRIVING, WHEN THEY WORK PEFECTLY WHEN GENERATOR IS RUNNING BUT NOT MOVING, I JUST BOUGHT THIS CLASS A IN OCT 2010. AND NEVER HAD A CHANCE TO TRY TO USE THE GENERATOR TO OPERATE MY ROOF AC UNTILL NOW, BEING THAT THE TEMP OUTSIDE ARE IN THE HIGH 90'S. MY GENERATOR WAS JUST SERVICED AND ONLY HAS 288HRS TOTAL TIME ON IT NOT USED TO MUCH!!!. EVERYONE I ASKED WHILE CAMPING SAY THAT THERE AC WORKS WHILE DRIVING, EXCEPT MINE. I HAVE A FEW IDEAS MAYBE TO MUCH AIR ACROSS THE CONDENCER COIL ON THE ROOF WHILE DRIVING. BOTH 13,500 BTU WORK FINE WHILE STANDING STILL WITH GEN RUNNING, I BLEW OUT THE CONDENCER COIL WITH MY COMPRESSOR. CAN ANYONE OUT THERE GIVE ME SOME HELP, I DID PURCHASE A FULL 4YR WARR WHEN I BOUGHT THE MOTORHOME, MAYBE I MIGHT HAVE TO USE MY WARR ON THESE AC. LOOKING FOR HELP ON THIS. THANKS

* This post was edited 08/19/11 12:41pm by zorro1421 *


Posted By: robsouth on 08/19/11 01:05pm

Please turn your Caps lock OFF! Thanks.


"Sometimes I just sit and think. Sometimes I just sit." "Great minds like a think."


Posted By: Mandalay Parr on 08/19/11 01:10pm

I don't know. That's a new one on me. Both of mine will run on gen while driving.

Yes, please turn caps off. It's like you are shouting


Jerry Parr
Full-time
2005 Mandalay 40B
Cat C7 350, 4 Slides
Blue Ox, Brake Buddy
2004 CR-V Toad
jrparr@att.net
602-321-8141
KG7EFA - Extra Class
Kenwood Radios


Posted By: Burp on 08/19/11 01:12pm

We may need more information to give an answer. What rig are you driving? Which generator do you have, what is its output? Dumb question, but will the genny run while you drive? That could be another issue all together. The rooftop ACs will not run off of the chassis motor, you have to run the generator while going down the road.

Welcome to the forum.


2007 Winnebago Voyage 33V (Workhorse, W20)
2008 Suzuki S83 (VS1400)

Me, the Wife , Sarah
Places we have camped in an RV



Posted By: aslakson on 08/19/11 01:27pm

Our MH has a circuit that turns off the electric to the front TV and associated electronics when the engine is running. Maybe the AC on this rig got wired into that circuit somehow.

Does the AC run on generator while standing still with the engine running?

al


Fulltiming since Apr 2007 in 2000 Rexhall Aerbus, towing 2012 Honda CRV. 44 of the lower 48 so far.


Posted By: pulsar on 08/19/11 01:48pm

Moved from Forum Technical Support to Tech Issues.


Posted By: smkettner on 08/19/11 02:07pm

As what point does the air turn off?

Start the gen and run the air.
Start the motor, put it in gear, start rolling. I assume the generator keeps running.... what triggers the air to stop?


2001 F150 SuperCrew
2006 Keystone Springdale 249FWBHLS
675 watts solar
Send a PM if I missed something


Posted By: ernie1 on 08/19/11 02:59pm

I had the same situation with my rv as I was headed towards Arizona. The chassis air blew a hose and so it quit working. I figured well, I'll just crank on the generator and fire up the roof top air. This worked for about maybe two miles as I was heading down the road when the ac would quit. I tried repeatedly to get the ac to work and had the same results.

On my return trip from Arizona back to California I got desperate and climbed up on the roof and removed the shroud around the ac and took off down the road. The ac worked flawlessly all the way back. I figured that the design of the rooftop on my rv and possibly the shroud on the ac combined to create an airflow problem and causing the ac to overheat and shut off. My present rv can be driven down the road and the ac will run fine. Both ac's were Dometic brand.


Posted By: zorro1421 on 08/19/11 03:05pm

type o unit is 2000 fleetwood bounder, onan marquise 5500 watt gen with two 13,500 ac units. both airs work fine on gen power, but when you start to drive the ac will go into the shed mode with the red lights on the thermostat. the gen was just serviced


Posted By: zorro1421 on 08/19/11 03:14pm

that is exactly what is happen with mine. we where heading from az to palm springs, i turned the ac on and about 3 miles down the road it went into shed. that was my thinking was that the condenser coil was get to much air, i cant think of the make of ac


Posted By: smkettner on 08/19/11 03:17pm

Could the water heater be cycling on? Will it never come out of load shead?
Seems like something else must be drawing power.


Posted By: zorro1421 on 08/19/11 03:19pm

i turned off the caps, when i run the ac with the generator and not driving everything works fine cold air until i start driving the ac turn off. i have a 2000 fleetwood bounder onan 5500 gen with 288 hrs and just serviced


Posted By: zorro1421 on 08/19/11 03:22pm

our water heater is on propane, and frig also the only thing run off gen is the ac and i only had one on


Posted By: wa8yxm on 08/19/11 04:16pm

While I can not tell you why it's not working. I can tell you this.

Too much air across the condenser coil is not possible. Absolutly NOT possible.

The only thing I can think of is a 12 volt issue, Often 12 volts is used to "Control" the air conditioner (Thermostat lines or in the case of some units the control computer) It may be that for some reason the A/C is on an interlocked circuit.


Home is where I park it.
Kenwood TS-2000 housed in a 2005 Damon Intruder 377



Posted By: pianotuna on 08/19/11 04:54pm

Hi zorro,

Are you turning the battery disconnect switch off?


Regards, Don
Full Time in a Kustom Koach Class C 28'5", 256 watts Unisolar, 875 amp hours in two battery banks 12 volt batteries, Magnum 3000 watt PSW inverter.


Posted By: MrWizard on 08/19/11 06:06pm

Red lights blink and load shedding starts , A/C is shut down

That sounds like power management system
Means either too much electrical load or the generator is having a problem producing enough power

Unless the A/C unit is over heating, its a generator problem
Either getting hot, or not getting enough fuel


Options, always have options, and the journey goes much smoother
....

Connected thru Verizon with HotSpot WiFi using a Samsung Galaxy Nexus



Posted By: dougrainer on 08/19/11 08:55pm

pianotuna wrote:

Hi zorro,

Are you turning the battery disconnect switch off?


Hope he answers. His problem is NOT the AC units and if his APU does NOT mis fire or run bad, it is NOT his APU as he states it works parked. His problem is his EMS system and it MUST be a 12 volt supply/control issue. I wonder if he has a miswire(wrong ground or positive to the wrong terminal) on his charge system when the Chassis engine is running. He needs to start the system (APU and AC's) let run for 10 minutes, then start the Chassis engine and let idle for 10 to 20 minutes. If the system does NOT malfunction, then drive and note when and how far/long it takes for the shedd to start. If it malfunctions at idle with the engine ON, then he must have a miswire of his chassis to coach charging system. And YES, he MUST have his battery disconnect ON. Doug


Posted By: MrWizard on 08/19/11 10:21pm

it wouldn't be the first time for a generator fuel issue when the drive engine is running

fuel return line issues, weak fuel pump, not enough fuel pressure while driving

low fuel level in tank or broken pickup tube and genny hiccups while running down the road


Posted By: ernie1 on 08/19/11 11:14pm

I'm thinking it's an airflow problem caused by the design of the roof relative to the position of the ac's where there is negative pressure rather than positive pressure to help push air across the condenser coils so that the ac's overheats and the unit shuts off. Remove the cover for one of the ac's and then take it down the road to see if it occurs again. If not, you have your answer. The solution?


Posted By: dougrainer on 08/20/11 07:04am

ernie1 wrote:

I'm thinking it's an airflow problem caused by the design of the roof relative to the position of the ac's where there is negative pressure rather than positive pressure to help push air across the condenser coils so that the ac's overheats and the unit shuts off. Remove the cover for one of the ac's and then take it down the road to see if it occurs again. If not, you have your answer. The solution?


Nice try, but in 32 years as a tech, this has NEVER happened or been an issue. ALL roof top AC units are basically designed the same and are made to be mounted on a roof for travel. REMOVING the cover is NEVER a good idea. Depending on the model, that will really overheat the AC as the cover is designed to be installed to make sure the fan pulls air thru the condensor. NO COVER on these models and no air gets pulled thru the condensor. Doug


Posted By: dougrainer on 08/20/11 07:05am

MrWizard wrote:

it wouldn't be the first time for a generator fuel issue when the drive engine is running

fuel return line issues, weak fuel pump, not enough fuel pressure while driving

low fuel level in tank or broken pickup tube and genny hiccups while running down the road


Thats true, but that would not really affect his EMS shed system. Doug


Posted By: zorro1421 on 08/20/11 08:57am

i thank everyone out there trying to help with my problem. you have given me alot to digest. as i mention i change the oil/filter both air and oil blew out the compart with my compressor, although did not change the fuel filter, and does the altitude ajustment have anything to do with it. i live in arizona at 1200 ft ele and the gen is set for 5000ft does that need adjustment. maybe it was a good thing i purchased 4rs warr when i bought this coach thru phoenix insurance, will they cover this problem


Posted By: MrWizard on 08/20/11 09:51am

Doug

AFAIK. the EMS uses to criteria voltage & current
If voltage drops , it starts shedding loads until correct voltage is reached
A generator with a fuel problem that cannot maintain speed to produce the amps the voltage will drop and trigger the EMS

THERE IS the possibly that alternator voltage is too high causing the EMS to malfunction

But I think the first is more likely


Posted By: ksg5000 on 08/20/11 10:10am

I am no electrical guru - but maybe you can use something like a Kill A Watt meter and have a passenger monitor the generator output as you drive? Also - since movement is one of the common denominators I would trace back the generator wires and make sure your electrical connections are tight/OK.


Kevin


Posted By: wa8yxm on 08/20/11 04:56pm

Doug,,, I have recently spent a lot of time on the roof of my rig looking at the GUTS of my Carrier Air V's.

Removing the top cover would make no difference in air flow over the condenser when parked, and might,, I stress MIGHT, improve it when moving.

It would, however, cause some other issues when sitting in the sun.


Posted By: dougrainer on 08/20/11 04:44pm

MrWizard wrote:

Doug

AFAIK. the EMS uses to criteria voltage & current
If voltage drops , it starts shedding loads until correct voltage is reached
A generator with a fuel problem that cannot maintain speed to produce the amps the voltage will drop and trigger the EMS

THERE IS the possibly that alternator voltage is too high causing the EMS to malfunction

But I think the first is more likely


IF the APU has a fuel problem, then the LOAD of the AC's will kill the APU before the EMS has time to act. Doug


Posted By: dougrainer on 08/20/11 04:48pm

zorro1421 wrote:

i thank everyone out there trying to help with my problem. you have given me alot to digest. as i mention i change the oil/filter both air and oil blew out the compart with my compressor, although did not change the fuel filter, and does the altitude ajustment have anything to do with it. i live in arizona at 1200 ft ele and the gen is set for 5000ft does that need adjustment. maybe it was a good thing i purchased 4rs warr when i bought this coach thru phoenix insurance, will they cover this problem


You have stated a lot but have yet to tell us what your system is REALLY doing.
1. Does the APU stay running in transit or does it die or run rough?
2. The APU runs at a set speed usually 1800 RPMs for an Onan. So, there is no reason to worry about the altitude adjustment. Changing the Oil/filters will NOT really do anything for a running problem.
3. IF your APU runs at parked status, then the APU is all to specs.
4. Did you do the tests I asked for?????? THAT will narrow down the problem. Post the results. Doug


Posted By: ernie1 on 08/20/11 06:12pm

Doug,
If you read my original post about removing the cover to my ac and the positive results I got, I thought I'd ask your opinion as to why I was able to run my ac while traveling and it ran for 14hrs straight. I'm asking you because you seem to be the more knowledgeable of matters concerning ac's and refrigerators. Yes, most rv ac's are built the same but the roofs on rvs are different. Mine was a Falcon class B with a sort of a large hump at the front on the top so I was thinking "vacuum".


Posted By: zorro1421 on 08/21/11 08:00am

Doug, i tried what you told me to do start apu run ac for 10 min, an attempt to run coach engine. as soon as i cranked the engine and when it just started, it was not a second later it went into shed solid red light. i install a xzantex 600 watt invertor which i tied into my engine battery,useing 00 cables would that have anything to do with it. the inverter is not on but connected. i use it only for sat box and tv when i do not want to run gen


Posted By: Jimf1234 on 08/20/11 09:18am

Zorro you are leaving the generator on while driving correct? The gen has to be on to power the ac.


2013 Sandpiper 365 SAQ


Posted By: dougrainer on 08/21/11 08:57am

zorro1421 wrote:

Doug, i tried what you told me to do start apu run ac for 10 min, an attempt to run coach engine. as soon as i cranked the engine and when it just started, it was not a second later it went into shed solid red light. i install a xzantex 600 watt invertor which i tied into my engine battery,useing 00 cables would that have anything to do with it. the inverter is not on but connected. i use it only for sat box and tv when i do not want to run gen


Good, That narrows it down to your Chassis to coach charging system. Disconnect the battery cable to that Inverter and retest. Connecting a Inverter to a Chassis battery system is not needed and not smart as the chassis battery is not designed to run Inverter type loads EVEN when the chassis alternator is on. Doug


Posted By: dougrainer on 08/21/11 08:59am

wa8yxm wrote:

Doug,,, I have recently spent a lot of time on the roof of my rig looking at the GUTS of my Carrier Air V's.

Removing the top cover would make no difference in air flow over the condenser when parked, and might,, I stress MIGHT, improve it when moving.

It would, however, cause some other issues when sitting in the sun.


If you read my post again you will see I stated "certain" AC models about the cover being off or on. Doug


Posted By: dougrainer on 08/21/11 09:03am

ernie1 wrote:

Doug,
If you read my original post about removing the cover to my ac and the positive results I got, I thought I'd ask your opinion as to why I was able to run my ac while traveling and it ran for 14hrs straight. I'm asking you because you seem to be the more knowledgeable of matters concerning ac's and refrigerators. Yes, most rv ac's are built the same but the roofs on rvs are different. Mine was a Falcon class B with a sort of a large hump at the front on the top so I was thinking "vacuum".


Depending on the model roof AC, you could get more air flow THRU the condensor with the cover removed, which will make it work a little better. The RV roof will have no real affect on the performance of the AC unit. Low profile AC units (penguins) that have wrap around condensors instead of square/recatangular condensors on the back require the cover to be ON, for the air to be pulled thru the condensor. Doug


Posted By: MrWizard on 08/21/11 10:10am

Zorro
Put a volt meter/multimeter on the battery with the engine on and check the voltage

Also try this test
Start the RV engine first, then attempt to start the generator
If it won't run its a fuel system issue
If it runs, turn on everything electric except the A/C

Let it and the engine run for ten minutes,
Now switch off the electric items and try the A/C

With enough items turned on incrementaly should be able to find out at what load the shedding starts


Posted By: zorro1421 on 08/21/11 04:13pm

doug, you have been very knowledgeable on this matter of mine, and i tried everything you sugested. read your last post about disconecting the pos lead from my engine battery to my xantrex prowatt inverter, i have not been able to get to my coach today to try. but can that cause this problem, what happen when i hooked it up like that.does it draw current from that battery even when the inverter is not turned on. i know a very little about electric but sound like your saying having it hooked up it is not completing a circuit. is that what your thinking. thank you again doug you have been very helpful, and maybe i wont have to take this in to the shop $$$$$$$


Posted By: dougrainer on 08/21/11 05:35pm

zorro1421 wrote:

doug, you have been very knowledgeable on this matter of mine, and i tried everything you sugested. read your last post about disconecting the pos lead from my engine battery to my xantrex prowatt inverter, i have not been able to get to my coach today to try. but can that cause this problem, what happen when i hooked it up like that.does it draw current from that battery even when the inverter is not turned on. i know a very little about electric but sound like your saying having it hooked up it is not completing a circuit. is that what your thinking. thank you again doug you have been very helpful, and maybe i wont have to take this in to the shop $$$$$$$


The reason I suggested the battery cable is YOU modified the system and I have NEVER seen such a problem. So, disconnect any add on appliances to get as close to the factory set up to see if the problem goes away. Also, it would help to have a digital voltmeter connected to the COACH 12 volt system either at the EMS board connection or at the COACH 12 volt fuse block to monitor what happens on the Coach 12 volts when you start your chassis engine. Also, I would like to know the chassis voltage at the chassis battery when your engine is running. That will check the Alternator ouput---maybe your alternator is putting out too high of a voltage (more than 14.2 volts). Also, try this. Have the system (APU and AC's off and not connected to shore power) Start the Chassis engine and THEN start the APU and then turn on both AC's to see if the shedd starts. Doug


Posted By: fatguy57 on 08/21/11 08:00pm

I have the same problem with my 05 Fleetwood Storm and my Onan marquis Gold 5500 genset. Recently had it serviced at Camping World, it has 470hrs and seems to work fine under load while parked and engine off. Get underway and try to use the AC, it drops off and AC goes to shed. I will add that the generator and AC worked while driving at one time.


Posted By: zorro1421 on 08/22/11 11:18am

Doug, Your the man!!. I tried what you suggested, i disconeced the inverter from the chassis battery, turned gen off ac off and everything else, then started the engine then the gen and waited about 5 min and started both ac, and nothing when into shed then I took the coach on the freeway for a test drive and the shed light did not come on while traveling at 55mph. when I get back, I turned the engine off, and the gen and ac kept on working fine until I turn the engine back on and the old results happened again, ac when into shed solid red light, not blinking red/green till ac starts. so I turned ac off then gen with engine still running, I followed step one again gen then ac and solid green light ac running no shed light. starting the engine draw that much 12volt to throw the ac into shed. i guess I will have to follow your instruction start engine, start gen wait 5min start ac.


Posted By: zorro1421 on 08/22/11 11:24am

fatguy57, Try what Doug told me to do and see if that might work for you


Posted By: fatguy57 on 08/22/11 02:42pm

I believe I found my problem and/or solution. It seems as if the Marquis Gold 5500 can only handle the two A/C's and nothing else (or at least the one I have). So I fired up the genset today while driving and only turned on the main cb, the A/C cb and the Climate Control cb. Left all the other appliance and misc. cb's off. Now my A/C's work while driving and did not drop off line. I left my refrigerator on propane gas. Previously, I was engaging all the cb's in the cb and fuse panel which for some reason I thought I had to do.


Posted By: zorro1421 on 08/22/11 05:14pm

Doug and MrWizard, thanks for the help with my ac gen problem. I disconected my inverter from chassis battery, Can you explain to me if I need to have both my main power and aux power switchs in the on posistion when driving. I can start my coach with both off. know one ever explained which ones to leave on when driving, when I purchased my rv. only turn them off when storing, I hate to sound stupid but I am new to this and want to learn the right way. I guess the only stupid answer is the one you don't ask.


Posted By: dougrainer on 08/22/11 05:43pm

BOTH disconnects MUST be ON. The ONLY time the disconnects are OFF is when you are stored and have NO 120 shore power available at the storage area. You should NOT be able to start the RV with both OFF. One is for the Chassis battery and the other for the coach battery. When the chassis is OFF, there should be no power to start the chassis engine. Doug


Print  |  Close