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Topic: AC turning off intermittently...  (Read 202 times) previous topic - next topic
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AC turning off intermittently...
I'm referring to the AC that runs from the dashboard, not the coach AC.  We've been on the road for several months and haven't used the cab AC much.  Lately we have though and notice that when the engine is under load (going uphill or accelerating) the AC shuts off - no air flow from the vents.  Is this normal on the E-450?  When the load from the engine is removed the AC comes back on.  Even more weird is the vent will turn off.

Thanks
Bob
2006 RK
Re: AC turning off intermittently...
Reply #2 –
Rich,

Thanks for the reply.  It’s a 2005 Ford E-450 engine.

Bob
2006 RK
Re: AC turning off intermittently...
Reply #3 –
Quote from: rprice  - 
Thanks for the reply.  It’s a 2005 Ford E-450 engine.

When cruising along on flat ground, the engine produces enough vacuum to operate the pneumatically-controlled HVAC system, when going uphill, the engine's vacuum drops to near zero. During this time, the HVAC system is operated by vacuum stored in the vacuum canister, the check valve prevents the stored vacuum from dissipating when the engine is producing little or no vacuum.
For those of you that are really old, you may remember vacuum-powered windshield wipers, they would speed up and slow down according to the available engine vacuum. Check valves and vacuum storage canister were still in the future. I remember my dad explaining to me, as a five-year-old, what caused the wipers to operate that way. Strange that I would remember this trivia from 66 years ago.

There are multiple things that can cause this problem, most have been mentioned. A failed check valve is common and the easiest repair. I have never seen a bad vacuum canister on an E450 but the hose fittings can crack.
Rodents seem to like the taste of rubber, I have worked on two LDs with the rubber vacuum hose either chewed away or nibbled on with small holes. A small hole(s) in the rubber hose, between the vacuum canister and the HVAC system under the dash, can produce a small leak and can cause an uphill problem.
Be glad you still have the rubber hose, on one LD, I found the rubber vacuum hose completely missing and had been chewed off to where the hose enters the interior through the firewall. It was a big job to get to the other side and patch in a new hose.

Larry
Larry
2003 23.5' Front Lounge, since new.  Previously 1983 22' Front Lounge.
Tow vehicles  2020 Jeep Wrangler Rubicon, 2001 Jeep Cherokee
Photo Collection: Lazy Daze
Re: AC turning off intermittently...
Reply #4 –
"Strange that I would remember this trivia from 66 years ago."
----
No, it is not.  ;)
2003 TK has a new home
Re: AC turning off intermittently...
Reply #5 –
Quote from: Joan  - 
"Strange that I would remember this trivia from 66 years ago."
----
No, it is not.  ;)

Ok, you are right, my brain is full of nothing but trivia.

Larry
Larry
2003 23.5' Front Lounge, since new.  Previously 1983 22' Front Lounge.
Tow vehicles  2020 Jeep Wrangler Rubicon, 2001 Jeep Cherokee
Photo Collection: Lazy Daze
 
Re: AC turning off intermittently...
Reply #6 –
What I meant was that we “seasoned” folks usually clearly remember a lot of details from decades ago; we’ve had a lot of years to fill up our hard drives with a LOT of information!  ;) 
2003 TK has a new home