Any fix for the way the ac cuts out when you put a big demand on the engine...like going up a hill??
Thanks.
Tim

 

Annoying design feature

 

Use the DRIVE setting for hills instead of OVERDRIVE-reduces the incidence of Wide Open Throttle (WOT) cut out by the throttle position sensor.

 

Yep, thats the only way.

 

It may be annoying, but its a lot better than blowing a head gasket by overheating the engine. You can fry the tranny too. Better to cut out than to ruin the engine.

 

I agree with khanty, better safe than sorry.

Ron

 

ie...better hot than hotter... :-)
Thanks for input..guess my option is......live with it.
Tim

 

Since I was just into this recently and had to stare at the wiring diagram: On the '90, one of the four relays on the left (driver's side) fenderwell is the A/C Wide Open Throttle relay. Wires to it: Red, Bk/Y, and I think Bk/G. Four wires only: if your relay has more than four wires, you have the wrong relay!

Either connect the two Bk/Y together (bypassing the relay) or ground the Bk/G (activating the relay at all times the Ign is on and A/C is on).

There is another way, over on the right side you could connect a wire between the normally-not-hot side of the pressure cycling switch to the not-ground wire of connector C104 (from memory, 3.0l only) that is behind the air filter housing at the bottom. But to me that's really more work than the other two methods, and the wire would be easy to mis-connect and do damage. The wire just does what the Bk/Y-Bk/Y jumper at the relay does.

When I was visiting Hot Country (to me, anyway) a couple of years ago, I was thinking hard about doing the same. The WOT cutout isn't to keep the rig from overheating, it's for an improvement in fuel mileage. One of the only aftermarket fuel-mileage-enhancing kits sold in the old days to be approved to work by the EPA was the same system: a diaphragm connected to manifold vacuum and a cutout switch. It was repeatably proveable that turning off the compressor load during acceleration increased fuel economy. Well, duh! But why have the A/C on if you don't want cold air (or defrost/defog)?

Regards,
Al S.

 

You think this one is bad.....Toyota's in the 70's used to shut off the compressor at idle speed......I think the threshhold was 750 rpm.....a real treat here in Texas if you are at a long light....

 

Al S.,

As I understand it the WOT relay is a normally closed relay which, in its unenergized state, allows power through to the A/C system. When the engine needs more power, the relay is energized by the EEC computer thus temporarily cutting power to the A/C system. Therefore, permanently energizing that relay would have the opposite effect and would permanently cut power to the A/C system.

Tim,

Fuel economy issues aside, it seems to me that if your WOT relay is cutting power to the A/C so much or so often that it has a serious negative effect on the ability of the A/C system to keep you cool, then either you are hauling too much for the engine you have or you need to adjust your driving style while towing. If you're not towing, then I'd suggest that you troubleshoot the WOT system to see if you have an intermittent short energizing the relay incorrectly or a bad EEC or throttle position sensor.

I would not suggest making any modifications to the wiring system to defeat the purpose of the WOT relay.

Just my 2cents.

Ron

 

The reason I say it is an annoying design feature is that my previous Aerostars, a 90 and a 94 did not cut out under load like my 96 does. I live in the southeast and have traveled the same roads with all three vans and I have a light foot on the accelerator. While we do have some hills they're nothing compared to mountains in the west. When I drive I59 from Birmingham to Chattanooga, one grade will knock out my cruse control and A/C.

Part of me thinks it may be a vacuum leak. I am waiting for the shop manuel CD that I bought off of Ebay, to arrive and then I plan to investigate all vacuum connections to see if I can find anything wrong.

 

Here is an idea. The engine load determines whether or not the ac cuts off. On our '92 Clubwagon, the ac would cut off a lot. Turned out that the TPS was going out, and telling the computer that I was applying WOT, when I wasn't. Also, check your MAP sensor if you have one, and a vacuum leak could be missinterpreted as engine load. Upgrade your exhaust to improve HP output and thus decrease the amount of throttle you need to apply. Have the AC pressure checked, as too much or too little pressure could also make the system touchy.

 

RLM: you could be right, I didn't probe the relay, I had a corroded connection and fixed that up, but I had to print out and memorize the color codes on that relay to get that far.

Khan: No MAP on the 96 I think, I suspect all went to MAF by then. Agreed on the TPS, they go bad as they are a variable potentiometer that gets a harsh workout. The three on the 3.0ls I've worked on that went bad all set a code, though. On my own, when it developed a dead spot, every time I'd hit that spot it would drop OD and light the CEL simultaneously. Code pointed directly to TPS. Others similar.

Regards,
Al S.

 

What's the symptom besides loss of A/C? Does the air not come out of the vents on the dash? If so, you could have a bad check valve in the vacuum line for the damper door. That's what it was in my case.

If you go to the dealer, expect to pay about $70 for the check valve assembly which is nothing more than the check valve and a few pieces of 1/8" nylon tubing that costs next to nothing. You might be able to find the part at a well stocked NAPA. I found mine at McMaster Carr and bought a lifetime supply of check valves and fittings for $14 including shipping.

You'll have to trace the vacuum line from the point it enters the dash back towards the intake manifold. It's a black and white piece about the size of a nickel in diameter. It will look similar to the check valve in the power brake line to the vacuum booster, only smaller in diameter.

The other possibility is a bad throttle position sensor. You could hook up an ohm meter and see at roughly what point the switch changes state (I think it closes). It could be changing state too soon.

 

My 93 aerostar does this when accelerating up hill's, it will be at full blast, then it would shut off. My previous car which was a 97 Ford Escort did the same thing, trying to accelerate up hills or just pass a car the AC will shut off. Im glad im not the only one who has this.