How do I disconnect A/C throttle?

Evil Joe · Aug 2, 2004

Cruising down the highway or idling in traffic, my A/C works great. However, whenever I accelerate, the A/C seems to turn off and the fan starts to blow (hot) outside air in. Is there any way to disconnect this feature?

(I've heard that the 5.0's have some feature to turn off the A/C to give the engine more power...but, I live in a hot climate - so I care more about cooling than performance!)

Thanks,

Evil Joe

1989 5.0 AOD

jerry beach · Aug 2, 2004

Are you sure it doesnt just stop blowing air at all? This is a common problem, the air cuts out under load. It is usually the air diverter door closing and not allowing air to pass across the evaporator. This is because the system is vacuum controlled. Under accleration (high vac. demand), you loose the vacuum that holds the diverter door open. Check, or have someone check for simple vacuum leaks first. I have a hand pump that cost $30. I can hook to the vac. lines and pull a vac., then look at the guage and see if it holds. I am almost sure that is what is going on with your car. HTH.

Evil Joe · Aug 2, 2004

Your description is very accurate and sounds like what is going on in my car. In fact, I always thought this was weird but, whenever I get in my car in the morning and turn on the engine...I hear a clunk coming from underneath the passenger-side dash.

Anyways, I'm a little confused on how to check for the leak...and more importantly, how to fix it. I also have a vacuum hand pump. Can you please explain in a little more detail which hoses to check and also, how would I go about fixing this problem?

Thanks so much.

Evil Joe

Idwitheld-1` · Aug 2, 2004

Evil Joe said:
Cruising down the highway or idling in traffic, my A/C works great. However, whenever I accelerate, the A/C seems to turn off and the fan starts to blow (hot) outside air in. Is there any way to disconnect this feature?

(I've heard that the 5.0's have some feature to turn off the A/C to give the engine more power...but, I live in a hot climate - so I care more about cooling than performance!)

Thanks,

Evil Joe

1989 5.0 AOD

Are you at wide open throttle (WOT) when the air kicks off? If yes, this is normal.

Mustang5L5 · Aug 2, 2004

Evil Joe said:
Your description is very accurate and sounds like what is going on in my car. In fact, I always thought this was weird but, whenever I get in my car in the morning and turn on the engine...I hear a clunk coming from underneath the passenger-side dash.

That's the MAX A/C door opening.

When in NORM A/C the blower draws air from the vent cowl taking in outside air, when you swithc to MAX A/C the door inside the cabin by the passenger's feet opens and it draws air from there.

As for the A/C cutting out at WOT, all cars do that. WHat controls it is the WOT relay located under the mass air meter on the pass side fender under the circle cutout on the fender. It's a small black box bolted to the fender with a wire harness plugged into it. Unplugging it will either do two things. The A/C won't work at all. Or the A/C will run all the time and never cut out on you at WOT.

Evil Joe · Aug 2, 2004

I will try pulling the WOT relay.

But, the problem occurs even under normal (or less than normal) acceleration. Seriously, unless I am going downhill and BARELY pressing the gas, the A/C cuts out and no air blows out. I hear the blower motor running...but no air is coming out. Air only starts to blow once I start cruising or idle.

jerry beach · Aug 2, 2004

You can hook the hand pump to the vac. lines and pull 10in hg on it. Should hold that for a few minutes and see if it leaks. This should tell whether the problem is in the interior or under the hood. You can pull the glove box down and see some of the vac. controlled solenoids. they can be tested with the pump too. Just dont over do it pulling a vac on anything like this. Take it for a drive with someone in the pass. seat and see if they can hear or feel that door closing down there. I have seen this so many times in fords.

HISSIN50 · Aug 2, 2004

to add to the spot-on info from others:

the WOT relay gets its input (to determine 'what' WOT is, from the TPS, IIRC). ive noticed that on several cars, the relay will kick the compressor clutch off, at more like 5/8 -3/4 throttle. you can hold the relay/watch the compressor clutch, while you rev the motor and see how far you get into the throttle before it kicks the clutch off.

i would not remove the relay - it is there for a reason.

my two cents. good luck.

Idwitheld-1` · Aug 2, 2004

HISSIN50 said:
to add to the spot-on info from others:

the WOT relay gets its input (to determine 'what' WOT is, from the TPS, IIRC). ive noticed that on several cars, the relay will kick the compressor clutch off, at more like 5/8 -3/4 throttle. you can hold the relay/watch the compressor clutch, while you rev the motor and see how far you get into the throttle before it kicks the clutch off.

i would not remove the relay - it is there for a reason.

my two cents. good luck.

Is it possible the low pressure (??accumulator??) switch is malfunctioning? I am taking my stang in tomorrow for the R134 conversion (I can't stand it anymore without AC!!!)

HISSIN50 · Aug 2, 2004

Idwitheld-1` said:
Is it possible the low pressure (??accumulator??) switch is malfunctioning? I am taking my stang in tomorrow for the R134 conversion (I can't stand it anymore without AC!!!)

Id, ill send you an email in a few mins - might check it before taking the car in. TTYS.

Evil Joe · Aug 3, 2004

OK - my problem is definitely vacuum related.

Behind the temperature control unit in the dash is a vacuum harness with 5 wires.

YELLOW - Goes to upper vent control
WHITE - For MAX A/C recirculation
BLUE - ??
RED - ??
BLACK - ??
?? = Leads up into the unknown.

If I hook a vacuum guage up to the yellow wire, it reads just over 10 at idle. If I rev the engine (in park) it dips slightly to about 8-9. But, under load it dips to less than 5 and sometimes 0.

So, this explains what is going on. Under load, the vacuum solenoid that controls the upper vent air loses vacuum and closes the upper vents. So, my blower keeps blowing but air doesn't come out. After I start idling or crusing, enough vacuum builds up to open the vents again.

So, I now know the problem, but, now, how do I fix it?!

1.) Where do the Blue, Red, and Black vacuum wires go?
2.) I have never troubleshooted a vacuum leak before. Can someone please offer some advice?

Thanks,
Evil Joe

ratrapp · Aug 3, 2004

if you can't find a vacuum leak then you may check to see if you have a check valve under the hood from where you get your vacuum source.if you don't have one then you can get a universal one from any parts store and add it inline with the vacuum source to see if it helps.

Ray III · Aug 3, 2004

I used to have this problem with my car's climate controls, the heat would never stay coming out of where it was supposed to if the throttle was open.

Took the front sheetmetal off, and under the passenger fender I discovered a vaccuum reservoir with a hose apparently leading into the engine by then thru the firewall for the climate controls. I believe this is where the BLACK hose goes.

The hose was broken and I suspect releasing all vaccuum as soon as engine vaccuum disappeared. Haven't got the car together yet so I don't know for sure. If you put your hand pump on BLACK, and cannot hold vaccuum after several pumps, you should look at that.

Evil Joe · Aug 3, 2004

Thanks for the suggestions so far...but, dude, I really dont want to pull the sheet metal off my passenger fender wall. Is there any other way to get to the canister?

Thanks,

Evil Joe

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