A while back I had a rodent do a number on some wiring and vacuum lines along the front end of intake manifold. I spliced in new wires in the repair. However, in repairing the hard plastic vacuum lines I had to substitute rubber vaccum hose as the local parts retailer did not carry the hard plastic stuff. I just inserted the good part of the existing vacuum line into the rubber hose. Now I seem to have a problem under load with the A/C. It will cut out under acceleration. Would the softer rubber vacuum lines cause this to happen. Should I just make a trip to the dealer to get some of the hard plastic line?

Your thoughts please...

 

i believe the AC is set to cut off under acceleration so you have more power to the wheels. Should have been that way from the factory.

 

The rubber hose repairs are fine, provided they aren't leaking.

Nope, I don't know of any designed like that in the last 40 or 50 years anyway, not intentionally for sure. He's not loosing it anyway, odds are that it is going to his defrost vents. If you want more power, turn it off. You may still have a vacuum leak, or, check your check valves that are close to the firewall behind the battery. There is a two hose, and two three hose ones. The resevoir behind the battery is the last in line. The check valve it hooks to also has the hvac vacuum line on it. Both of them are on the checked side of the check valve, ie they have a common plumbing. The other line is the vacuum.

Goes like this

vacuum<resevoir and hvac

that way the vacuum can vacuum it, then it closes when the vacuum tries to go the other way. That way, when the engine looses vacuum, ie under accel in your case, the hvac never looses it. UNLESS it has a leak, otherwise it should be fine.

If you rule it down to the valves, pull them out one at a time and suck and blow on them to see if they are working. I have seen them stick closed before. In that case though you wouldn't have control of your vents, ever.

OR if you have climate control and not ***** for the a/c, disregard all of this. You need to do some searching on here for some pictures of the Climate controller and oring replacement on it. The orings on them dry up and they leak vacuum. They have the same effect, just different diagnostics.

 

I have a 97 F150 that is doing the same thing. I just went through a problem with a vacuum leak which was fixed after I replaced the PCV valve hose. My AC goes from ice cold to hot upon giving it the gas. Don't know if it related or not but my gas mileage is down to about 7 MPG after fixing the broken hose.

 

FYI...

Prior to the rodent event the A/C always worked great... even under hard acceleration, so "cutting out" is NOT how it is supposed to be "from the factory". I suppose I'll just have to recheck all the vacuum lines again.

@jyount - I will look at what you suggest as that area is where the rodent set up house.

 

Just as suggested I traced the errant vac line from the firewall to a "box" attached to the rear of the battery shelf. 98 cents worth of vacuum hose and the problem is solved. The A/C is healed.

Question though: what is this "box" attached to the rear of the battery shelf?

 

Glad you're fixed. That "box" is the vacuum reservoir. It keeps vacuum for the hvac system when the engine has none, is when the throttle plate is opened up. Wider plate angle, less vacuum. You make the most vacuum idle. Less and less as you open the throttle more and more....