Cab A/C turns off when going up hill

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Cab A/C turns off when going up hill

July 15, 2017, 04:50:58 pm

Hi All,

I have just noticed this week (driving from AZ to CA through Yuma) that when going up a mountain road that the cab a/c turns off and then turns it self on again at the crest of the hill. It feels like it is blowing hot but the fan is not on but the cab gets very warm. On the next hill I was climbing and it turned itself off I let up on the gas and it came on again for a moment or two. So I think it is a vacuum problem. This doesn't happen on every hill. Anyone experienced this? Is there an inexpensive fix?

I think this question or a similar question came up a while ago but my search could not find it. Or it may be my mind playing tricks on me.

Thanks

Kevin

Re: Cab A/C turns off when going up hill

Reply #1 – July 15, 2017, 05:58:53 pm

Kevin

I think that you and your Lazy Daze have a symbiotic relationship and perhaps it's trying to tell you something.

I have, for more years than I can remember, always turned the A/C off when I'm climbing a grade because that compressor is stealing power from your engine. And now that my daughter, Lazy Bones 2, has more or less taken over in the Captains chair I caution her to dump the A/C until she's on a down grade.

Re: Cab A/C turns off when going up hill

Reply #2 – July 15, 2017, 06:04:52 pm

Most Engine Control Computers ECC (Eek) control the Chasis Air Conditioning also. At Wide Open throttle the ECC Turns the Compressor off for maximum power to the wheels

The other thing that turns the compressor off is compressor presure switch. When the Suction side pressure drops to 25psig the compressor is turned off. This can occur at high engine RPM. This also occurs when the system has lost Freon.

Re: Cab A/C turns off when going up hill

Reply #3 – July 15, 2017, 06:50:25 pm

Kevin, my money would be that it's a vacuum problem. The older your rig is the more I would bet on it. The AC does not cut off, but the doors that allow air to come out the vents close, so it seems that way. There is still cool air at the floor. The fix will not be cheap. It's labor intensive as the hose is buried and requires removal of a lot of stuff to access it. Done at a dealership you may pay close to 4-digits.

Re: Cab A/C turns off when going up hill

Reply #4 – July 15, 2017, 07:17:08 pm

Quote from: kevin hannah - July 15, 2017, 04:50:58 pm

Hi All,

I have just noticed this week (driving from AZ to CA through Yuma) that when going up a mountain road that the cab a/c turns off and then turns it self on again at the crest of the hill. It feels like it is blowing hot but the fan is not on but the cab gets very warm. On the next hill I was climbing and it turned itself off I let up on the gas and it came on again for a moment or two. So I think it is a vacuum problem. This doesn't happen on every hill. Anyone experienced this? Is there an inexpensive fix?

I think this question or a similar question came up a while ago but my search could not find it. Or it may be my mind playing tricks on me.

Thanks

Kevin

We have the same issue and I believe it is a vacuum leak. Take a look at this thread and especially the link contained within to the sportsmobile website. We haven't fixed ours yet but it is on the agenda.

Air flow problem, vacuum leak?

Jim

Re: Cab A/C turns off when going up hill

Reply #5 – July 15, 2017, 07:54:44 pm

Is there a simple way to check for a vacuum leak just to see if there is a problem one may not know about?

Re: Cab A/C turns off when going up hill

Reply #6 – July 15, 2017, 09:39:39 pm

Quote from: kevin hannah - July 15, 2017, 04:50:58 pm

Hi All,

I have just noticed this week (driving from AZ to CA through Yuma) that when going up a mountain road that the cab a/c turns off and then turns it self on again at the crest of the hill. It feels like it is blowing hot but the fan is not on but the cab gets very warm. On the next hill I was climbing and it turned itself off I let up on the gas and it came on again for a moment or two. So I think it is a vacuum problem. This doesn't happen on every hill. Anyone experienced this? Is there an inexpensive fix?

I think this question or a similar question came up a while ago but my search could not find it. Or it may be my mind playing tricks on me.

Thanks

Kevin

My 2002 does the same thing.

Re: Cab A/C turns off when going up hill

Reply #7 – July 15, 2017, 11:05:29 pm

"I have, for more years than I can remember, always turned the A/C off when I'm climbing a grade because that compressor is stealing power from your engine. And now that my daughter, Lazy Bones 2, has more or less taken over in the Captains chair I caution her to dump the A/C until she's on a down grade.

"

With training from dad and first hand experience I can tell you this works. If A/C is on when going up a grade thr engine boggs down, turning off A/C until you are level or going down hill makes a big difference to us in a 30'IB and towing 😉🚐

Re: Cab A/C turns off when going up hill

Reply #8 – July 16, 2017, 09:33:09 am

Ultimately, I think Kevin needs to determine whether or not the compressor is being turned off by design to evaluate whether this is a 'bug or feature' of the vehicle. Sometimes deep reading of the owner's manual or reviews/tech literature of the time will reveal all. Since it still blows air, just not cold, I wouldn't think vacuum actuation of air doors would be the issue. (Although if it's the external/recirculate door, that could be a valid point...)

Usually the AC's electric clutch is turned on by a 12V signal. If you can pinpoint that wire, and put a temporary indicator light (visible from the driver's seat while underway) on it, that will 'shed some light' on what the compressor is being told to do.

Just had my wife's Volvo Cross-Country in the shop last week for a similar 'intermittent AC' issue, except it was random and not load-related. Turned out to be shims in the AC clutch. Diagnosed correctly over the phone by the shop upon scheduling, and fixed for less than $200. Not a new clutch, just some benchwork on the existing one. Anecdotal to be sure, but not everything AC related is $1K...

Chip

Re: Cab A/C turns off when going up hill

Reply #9 – July 16, 2017, 10:48:38 am

Quote from: kevin hannah - July 15, 2017, 04:50:58 pm

Hi All,

I have just noticed this week (driving from AZ to CA through Yuma) that when going up a mountain road that the cab a/c turns off and then turns it self on again at the crest of the hill. It feels like it is blowing hot but the fan is not on but the cab gets very warm. On the next hill I was climbing and it turned itself off I let up on the gas and it came on again for a moment or two. So I think it is a vacuum problem. This doesn't happen on every hill. Anyone experienced this? Is there an inexpensive fix?

I think this question or a similar question came up a while ago but my search could not find it. Or it may be my mind playing tricks on me.

Thanks

Kevin

A sign of a vacuum leak is the air stops coming out of the dash vents under and diverts to the windshield defrost. Don't know if you looked for that or not. That is what we find happening and an indicator you will see mentioned in the link I listed earlier.

Jim

Re: Cab A/C turns off when going up hill

Reply #10 – July 16, 2017, 11:38:23 am

Wow! Thanks for all the responses. We lived in WA state and did not notice the A/C going off. Once we moved to AZ (hotter temperatures) we are now noticing it. I will check for an air leak. I checked on Google and there was a similar question and an answer on how to check for an air leak. We can live with it and turn the A/C off when we drive mountain roads. Just wanted to know what was happening and if anyone else here was experiencing the same thing.

Thanks for the input. I greatly appreciate it.

Kevin

Re: Cab A/C turns off when going up hill

Reply #11 – July 16, 2017, 08:14:07 pm

I had similar issue with our 2004 Toyota Van, low on Freon, fixed, going strong after 4 years

Bob Wilson

Re: Cab A/C turns off when going up hill

Reply #12 – July 16, 2017, 08:25:34 pm

The HVAC's vent and duct controls are powered by engine vacuum. Engine vacuum decreases to near zero, under full throttle.
To maintain the HVAC's vacuum supply, during full throttle operation, vacuum is stored in a container, with check valve (one-way valve), located in the vacuum supply line, between the engine and storage container. The check valve prevents vacuum from being lost during low vacuum situations.

Losing the A/C, at near or full throttle, may be caused by a failed vacuum check valve, in the HVAC vacuum supply.
Not sure if it is installed under the hood or under the dash.
If under the hood, it can be accessed and replace easily. If under the dash, leave the bad valve alone, instead, add another inline check valve, under the hood, in the vacuum supply line. Either that or an very expensive job of removing the dash.

You can test for a bad check valve by turning the engine off, waiting 30 minutes and then, without starting the engine, moving the HVAC control to a new position, listening for movement under the, dash, indicating that stored vacuum is still present.
If you hear nothing, good chance the check valve has failed.
The HVAC controls should normally operate the controls after sitting a day or more.

On the E450s, the vacuum supply line runs from a port, on the intake manifold, to the passenger side of the firewall, entering the interior somewhere in back of the A/C blower housing.
Look for a thin, 1/8" black plastic tube. One end leads back the the intake manifold.
Here is a photo with the vacuum line marked with a strip of yellow tape.

Larry

Re: Cab A/C turns off when going up hill

Reply #13 – July 16, 2017, 08:53:40 pm

Amazing. Has Larry ever been stumped with a Lazy Daze question? What a resource to us all! Thank you Larry.

Re: Cab A/C turns off when going up hill

Reply #14 – July 17, 2017, 02:20:17 am

Years ago with our our first motorhome, Fleetwood Jamboree E350, and living in Sacramento we were advised to turn off cab air when doing a climb. If it is hot we run the generator and turn on the AC which takes care of exercising the generator and keeping us cool. Our 2005 LD generator has about 380 hours on it and has kept us comfortable during summer trips. We have run it 8-10 hours continuously on numerous summer trips.

Mary Sue
26.5' Island Bed

Re: Cab A/C turns off when going up hill

Reply #15 – July 17, 2017, 05:19:21 pm

This discussion brings back memories of riding in my buddies old Rambler with vacuum wipers. What an experience when he decided to pass another car in the rain!

Re: Cab A/C turns off when going up hill

Reply #16 – July 17, 2017, 05:52:37 pm

Quote from: folivier - July 17, 2017, 05:19:21 pm

This discussion brings back memories of riding in my buddies old Rambler with vacuum wipers. What an experience when he decided to pass another car in the rain!

Growing up, I remember seeing kits advertised to replace the finicky vacuum wipers with new electric motors.
Uphill, in the rain, on a dark night, ah, those were the days (scared half to death in the back seat).
No seat belts either.
It's a miracle any of us survived growing up.

Larry

Re: Cab A/C turns off when going up hill

Reply #17 – July 17, 2017, 06:03:48 pm

Quote from: M.S.Ferrell - July 17, 2017, 02:20:17 am

Years ago with our our first motorhome, Fleetwood Jamboree E350, and living in Sacramento we were advised to turn off cab air when doing a climb.

This is where an accurate temperature gauge comes in handy.
The E450 cooling system is fairly large and mostly does a good job.
I watch the ScanGauge like a hawk, in hot weather, and can't remember turning the A/C off more than once or twice due to the coolant temperature getting too high.
As for the A/C using a significant amount of power, I don't feel much of a difference in uphill climbs, turning it on and off.
I do hear a loud whining, from the right side of the cab, when the A/C is shut off, that negates any slight increase in speed.

Larry

Re: Cab A/C turns off when going up hill

Reply #18 – July 17, 2017, 06:12:20 pm

"Uphill, in the rain, on a dark night, ah, those were the days (scared half to death in the back seat). No seat belts either. It's a miracle any of us survived growing up."
----
Hey, I didn't know you had driven with my mother!

During the war, it was a most of the night trip from the central coast to L.A. to visit my father in the TB sanitarium; "blackout" headlights, Mama's pack of Pall Mall cigarettes in the visor, and a little girl standing up in the front seat, peering out the windshield, enduring frequent flings of the "Mom arm" to keep me from pitching into the dashboard. Yes, sometimes I wonder how some of us made it, too!

Re: Cab A/C turns off when going up hill

Reply #19 – July 17, 2017, 08:48:24 pm

Quote from: Larry W - July 17, 2017, 05:52:37 pm

Growing up, I remember seeing kits advertised to replace the finicky vacuum wipers with new electric motors.
Uphill, in the rain, on a dark night, ah, those were the days (scared half to death in the back seat).
No seat belts either.
It's a miracle any of us survived growing up.

Larry

My first car was a '46 Chevy pickup with the old crank out windshield. Although the running gear was updated, the wipers were still vacuum. I eventually replaced them with electric wipers. Much better!

Re: Cab A/C turns off when going up hill

Reply #20 – July 18, 2017, 10:22:20 am

Thanks Larry, that explains a lot. I always appreciate your insight and input. I will be taking the LD in for service today and have them look at the air conditioner as well as a starting problem on the generator. They fixed the generator a couple of weeks ago as it was not supplying electricity to the motorhome. It was a loose wire. Now it does not start, maybe fuel pump. Anyway I have printed out your reply and will show it to them and have them look at the A/C at the same time. I started the LD yesterday and will check the vents this morning before starting it to see if it still has vacuum.

Thanks again.

Kevin

Re: Cab A/C turns off when going up hill

Reply #21 – July 18, 2017, 09:04:31 pm

Quote from: folivier - July 17, 2017, 05:19:21 pm

This discussion brings back memories of riding in my buddies old Rambler with vacuum wipers.

Chris - did we know each other in a previous life? My first car was a Rambler (wagon) with vacuum wipers! (and foot-pump windshield washer)

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