Dash air quits when going up hill

[ELVERDA]

The air stops when throttle is increased on hill. Fan stops and no air until I go downhill. Could this be a vacuum problem?

Doc

 

[Wizard46]

If a gas engine its possible. I little more info on engine, chassis and model may help

 

[John Canfield]

^^ exactly ^^  Welcome aboard.

 

[PJ Stough]

I believe an "air conditioner cutout switch" was used on some Ford engines.

Paul

 

[BobNSam]

If gas engine...
Does fan stop or do you find that no air from AC vents - check if air is actually coming from defroster vents instead.
If as above it is a vacuum leak, either cracked hose or bad vacuum reservoir. Under heavy acceleration manifold vacuum decreases and check valves and a vacuum bottle help retain accessory vacuum. AC cutout switch only turns off compressor, not fan
If not as above, i.e. fan actually quits, expect wiring or bad fan motor.
If diesel...someone here can help.
Bob

 

[Gary RV_Wizard]

The a/c cutout is a normal function, but it may be triggering early or inappropriately in your case. Basically the ECM shuts off the a/c to reduce the power demand on the engine as well as the heat the radiator has to deal with. The dashboard a/c is a major source of both heat and horsepower demand. So, the difficult question is whether your engine is underperforming and thus the engine computer is forced to cut the a/c off when normally it would not. Some of the possible reason this might happen include poor fuel quality, bad spark plugs, clogged fuel filter, and bad spark plug wires. Anything that causes a loss of power could force the engine computer to take extreme action on hills, when the load gets heavy.

 

[ELVERDA]

2000 workhorse w chev 454 p32 I think, this unit had only 16000 miles and I believe it wasn't run for five years in shed.

Thanks for all the help. New user.

Doc

 

[SCVJeff]

The FAN cuts out or it just quits cooling?

 

[driftless shifter]

You probably have vacuum operated heat A/C controls. Pulling a hill with your foot on or near the floor, a gas engine makes almost no vacuum. The vacuum canister is likely the size of a grapefruit. There are probably some minor vacuum leaks in the vacuum plumbing, the EFI can accommodate without issue. When vacuum in canister is gone,the heat A/C controls default to the the defrost vents on dashboard. You cant hear the blower running over the sound of the engine roaring under the doghouse and assume the fan quit working. Next time it happens feel for A/C blowing out of dash vents. Before you tear into the spaghetti of color coded hard plastic vacuum lines behind your dashboard heat A/C controls look for the vacuum canister behind the right headlight, in the fender well somewhere, and check the rubber vacuum line from end to end for dry rot at the connections. It will go from the vacuum canister to the top of the engine near the throttle body and the dry rot will most likely be at the ends where it makes connections. There may be enough slack that you can just snip the ends back to more pliable hose and reconnect it. It is easy to do but a mechanic will either overcharge you or screw with the spaghetti under the dash and make things worse.

Bill

 

[carson]

Old- timers will remember cars/trucks with vacuum operated wind

shield wipers.  The same thing happens with them... no wiper action.

 

[Gary RV_Wizard]

Good point about the vacuum operated controls and that's a possibility, though I haven't heard of that issue since the 70's. It's for sure, though, that the ECM will turn off the a/c compressor if the load on the engine gets too high, or if the engine begins to overheat. It's programmed to do that in most modern engines.

 

[carson]

My 1995 Wini Adventurer had vacuum controlled heat?A/C air valve gates

 

[BobNSam]

Good point about the vacuum operated controls and that's a possibility, though I haven't heard of that issue since the 70's. It's for sure, though, that the ECM will turn off the a/c compressor if the load on the engine gets too high, or if the engine begins to overheat. It's programmed to do that in most modern engines.

My 2004 Winnebago had cracked tubing at the canister that caused the problem of air going to defrost vents instead of AC vents. So did an '89 Cougar.
Bob

 

[driftless shifter]

Pretty sure you have vacuum controls. Does your control panel look like one of these?

http://www.evanstempcon.com/ownersmanuals.php

If so check your engine and canister vacuum lines.

 

[ELVERDA]

Thanks for all the help.

 

[1Sammiedog]

Try reading this post on another forum for some help.

http://www.irv2.com/forums/f101/vacuum-line-leak-anyone-44852.html

1Sammiedog