A/C cuts out when engine is under load
Graeme McRae
works OK until the engine is under a sustained load, such as driving up a
long hill on the freeway. While we're going up that hill, the A/C blows hot
air. Immediately after cresting the hill, the A/C starts working again. He
took it in for service, and it was low on freon, but that didn't fix the
problem. Compressor works fine, cycles on and off as needed, freon is OK,
no leaks. We thought the engine might be overheating, causing some sort of
failsafe mechanism to turn off the A/C compressor to prevent excessive
overheating, but that seems unlikely because the temperature gauge stays
nicely in the middle during the whole trip up that big hill. Any thoughts?
--Graeme McRae
Basil Mournian
Cressida. I was driving about 70-75 miles per hour on a slight grade
on the freeway, and the heater started blowing cold air. Not only
that, but outside air started blowing in through the vents with it on
the recirculate setting.
I think what you are experiencing, and what I was having going
on with my car is vacuum-related. I don't know if it can be fixed,
but there is probably a vacuum-actuated water control valve under the
hood of your car, and when engine vacuum decreases, as when you are
driving with a load on your car, it takes away vacuum from the
actuator valve, which causes warm water to circulate through the
heater core, which in turn heats the output air. Hope this possible
solution helped you understand what's going on with your car.
Basil M.
On Wed, 22 Jul 1998 23:49:55 -0700, "Graeme McRae" <mc...@ptw.com>
wrote:
Post...@postoffice.worldnet.att.net
>
> My carpool partner has a Toyota Camry, 1992, I think, whose air conditioner
> works OK until the engine is under a sustained load, such as driving up a
> long hill on the freeway. While we're going up that hill, the A/C blows hot
> air. Immediately after cresting the hill, the A/C starts working again. He
> took it in for service, and it was low on freon, but that didn't fix the
> problem. Compressor works fine, cycles on and off as needed, freon is OK,
> no leaks. We thought the engine might be overheating, causing some sort of
> failsafe mechanism to turn off the A/C compressor to prevent excessive
> overheating, but that seems unlikely because the temperature gauge stays
> nicely in the middle during the whole trip up that big hill. Any thoughts?
>
> --Graeme McRae
Yeah it sounds like the vacuum motor on the blend-air door is leaking.
Rick Leblanc
I don't know anything about Toyotas but I am aware that North American
cars as well as my Mazda MPV, will all disengage tge AC compressor at
wide open throttle (WOT). Apparently this is to give you all the
available horsepower when you need it.
Up till now I thought this only occured at WOT but it may also happen
in other situations such as sustained loads.
--
Rick Leblanc
rrle...@bconnex.net
To Reply please remove the first "r" from my return address
Who Cares?
> My carpool partner has a Toyota Camry, 1992, I think, whose air conditioner
> works OK until the engine is under a sustained load, such as driving up a
> long hill on the freeway. While we're going up that hill, the A/C blows hot
> air. Immediately after cresting the hill, the A/C starts working again. He
> took it in for service, and it was low on freon, but that didn't fix the
> problem. Compressor works fine, cycles on and off as needed, freon is OK,
> no leaks. We thought the engine might be overheating, causing some sort of
> failsafe mechanism to turn off the A/C compressor to prevent excessive
> overheating, but that seems unlikely because the temperature gauge stays
> nicely in the middle during the whole trip up that big hill. Any thoughts?
>
> --Graeme McRae
>
Some cars will temporarily shut off the A/C compressor when under wide
open throttle or under low vacuum conditions. Could yours be doing
the same? It could also be misadjusted so that it kicks out at a much
lower throttle setting.
Kevin Mouton
> My carpool partner has a Toyota Camry, 1992, I think, whose air conditioner
> works OK until the engine is under a sustained load, such as driving up a
> long hill on the freeway. While we're going up that hill, the A/C blows hot
> air. Immediately after cresting the hill, the A/C starts working again. He
> took it in for service, and it was low on freon, but that didn't fix the
> problem. Compressor works fine, cycles on and off as needed, freon is OK,
> no leaks. We thought the engine might be overheating, causing some sort of
> failsafe mechanism to turn off the A/C compressor to prevent excessive
> overheating, but that seems unlikely because the temperature gauge stays
> nicely in the middle during the whole trip up that big hill. Any thoughts?
>
> --Graeme McRae
I'm not that familiar with the 92 Camry, but most 4 Cyl. cars made since the
late 80's have a Wide Open Throttle cut out switch that turns off the A/C
compressor. I know that Ford's system uses a timer that will turn the compressor
back on after 15 seconds if the throttle remains wide open that long. Perhaps
you could check with a Toyota Dealer service department to see if your Camry is
supposed to do this.
Usually the Compressor cut off function is integrated with the Electronic Engine
Control computer, so there may be a way to check for problem codes on your
model.
You may also have a vacuum operated air blend door problem. If there is a vacuum
leak in the A/C system controls, the damper door that closes off air flow
through the heater core when A/C is selected, may be malfunctioning when the
intake vacuum is low at Wide Open Throttle.
Either one of these two problems would require a Tech that is very experienced
on Toyota systems, to diagnose it properly. I would definitely ask the service
writer at what ever shop I brought it to for a technician that is certified on
Toyota A/C systems to work on my car.
Kev
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************************************************
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************************************************
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gerald zuckier
>
> My carpool partner has a Toyota Camry, 1992, I think, whose air conditioner
> works OK until the engine is under a sustained load, such as driving up a
> long hill on the freeway. While we're going up that hill, the A/C blows hot
> air. Immediately after cresting the hill, the A/C starts working again. He
> took it in for service, and it was low on freon, but that didn't fix the
> problem. Compressor works fine, cycles on and off as needed, freon is OK,
> no leaks. We thought the engine might be overheating, causing some sort of
> failsafe mechanism to turn off the A/C compressor to prevent excessive
> overheating, but that seems unlikely because the temperature gauge stays
> nicely in the middle during the whole trip up that big hill. Any thoughts?
>
> --Graeme McRae
when you are going full throttle, you probably can't spare the power. It
is only noticeable on sustained long hills, etc. Nowadays it's in the
computer, you'd have to do some creative wiring to bypass it. JCWhitney
used to sell a separate vacuum switch for just this purpose; it was
supposedly the only aftermarket fuel saver gadget that was tested and
verified by the DOT or some such.
eagle
key all the way but not to turn the car on, and turn fan on, thats how fan
works with high load. I, when my ac fan burned up, and the ac relay messed
up, installed the same rellay in permanent mode. ac doesnt turn off when
power steering is full, or in turns or on any other occasion. That was the
only way to fix it, so i dont know the effects that it can cause, that i
think it wont.
Graeme McRae wrote in message <35b64...@news.ptw.com>...
Robert Erck
<ea...@coqui.net> wrote:
--------------
Almost all cars cut off the AC compressor when the throttle is near max.
That is so you have more power when you need it.