Hi,
Living in AZ, you need the ole A/C these months. I have a 91 Bronco 351W and the A/C seems to be a little temperamental. The A/C is cold however I have two things I would like to fix and if anyone knows a direct cure for the problems, please let me know.

1. When traveling down the road, A/C is running fine but when the gas pedal is pushed for more speed, the dang A/C goes from Max A/C vents to the defrost vents. When I let up the gas pedal, it returns to the dash vents where I need it most in this 110 degree weather. This seems to be a ford thing becuase I had an 89 Thunderbird SC and it did the same thing.

2. A/C is cold but the fan sucks. I get in come vehicles and it seems I am in a cold wind tunel test but in the Bronco, the setting high means low-med in some vehicles. Do I need to get a new fan or is there a way to turn up the juice to the fan for higher air flow out. As you know, the interior is rather large and with a BLACK Bronco in the hot desert, it does not cool the whole interior no matter how long I drive.

Any inputs are greatly apprciated.

 

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Welcome. You came to this forum for the same reason I did.
Short answer to 1....(a.) Either the little check valve assembly is not holding the vacuum high to the a/c doors when the engine vacuum drops at full throttle or (b.) vacuum hose is leaking or (c.) not very likely but could have big vacuum leaks at one of the resevoirs, or charcaol canister purge selenoid may be stuck open. There are many threads on this subject. Click on my name and see other postings by me. Check the back and white spaghettie size hoses under the hood near the blower motor first. If you don't find the leak get the tester.
Short answer to 2. ..My red gets hot in Texas. Red is only a little cooler than black. Once I get the vacuum resolved air will be COLD out of the vents even with the new freon but not very much air flow.. Be sure all are open and pointed straight forward. Turning them reduces the flow. BTW my Buick LeSabre started doing the same thing.

 

Thank you for the welcome. Thank you for the threads. I have talked with some professionals and they seem to be stumped on #1. They say #2 is normal for Broncos but I believe "if there is a will, there is a way" to improve the fan speed and output flow. The A/C is cold but little fan speed/output. Do I have to replace the fan motor to a larger size or is there an adjustment?

I'll check out your advice on #1 b4hntn this weekend. I don't think if #1 is fixed, it will fix number #2 because the A/C is already cold. It just doesn't have high output and it always was that way before #1 problem was there. If I have anything positive, I will be sure to post.

Thank you.

 

You will be very pleasantly surprised at the difference once the A/C doors stay put on heavy throttle. On #2 do all the different fan speeds work? I understand there are resistor coils inside below the fan blades but they would be there to slow the motor.

 

You can't really boost the fan. On high it's getting the full 12 volts already. The blower resistor is only for reducing power to the fan to achieve the lower speeds. I would pull the fan out and inspect it for pine needles, cat hair, lint, paper, and various crap that might have sucked in through the cowl. I've found all of the above stuck in fan blades. You can't blow air with fan blades gummed up.
My 87 cools just fine. It does in fact take it while to get there but once cool I'm happy enough.
For problem #1 I suspect the check valve just before the vacuum canister.

 

My Bronco does the same thing with the defrost. I am not famaliar with vacuum at all. Where is this check valve and what vacuum canister?

 

On my '94 the a/c vacuum cannister or reservoir is plastic attached to the a/c box and next to the transmission dip stick. Coming from the cannister, the black hose on mine was rubbing on something and had a hole in it. The hose attaches to the check valve. The other small hose from the check valve goes to the a/c heater controls inside the cab. The larger hose goes toward the engine. Many threads said the white hose may crack first. The black one to controls and white one go in the same wiring harness side by side. The check valve at dealer was about $11 and the MihtyVac vacuum tester at AZ was about $28 and worth three times as much.

 

Okay. It used to be that when I barley got my rpm's up it would switch to defrost. I already have a tester and I found that the black and white lines were not holding. I replaced them from the cab clear to the firewall. I also replaced the line coming off the intake vacuum tree to the little check valve. Now if I drive normal it does not go to defrost, but when my rpm's get to about 3500 or so it switches. Hmm? I did not find any more leaks, but I guess I will have to check again tonight.

 

Is the vacuum canister that is attached to the a/c box suppossed to hold a vacuum? I did not pick up any, but the box does not seem to be damaged any.

 

Yes, It look a lot of pumping with my MihtyVac to get the vacuum up (or is is down?) on the a/c cannister but when finally up it held.

 

I probably pumped mine 20 times and still no hold. Does it serve the same purpose as a vacuum ball? I woder if I could just hook the black line to a ball and bypass the canister.

 

Sounds good to me but sure would be embarrising to put a chebby one on it. I may have pumped 20-25 times.

 

replace the vacuum hoses on passenger side of the engine compartment. Both my 90 and a friends 92 suffered from the same malady. I had already discovered mine when his a/c started acting up; so we were able to diagnose his immediately. Subsequently I actually ended up replacing all that plastic line in the engine compartment with rubber vacuum hose...I would actually recommend that...it seemed to make everything just work better all around.

I also installed a shutoff block valve for the water heater system When I tore my system apart while converting to R-134 I noticed that; even though everything was functioning fine, some of the plastic doors inside the assembly did not really seal well. SO, I installed the shutoff valve to keep hot water from traveling through the heater assembly....before I did that there was also some hot air blowing through the vents. My buddy with a 92 had to do the same thing to stop that hot air.

 

I have all ready replaced all of the vacuum hoses on my passenger side. I also installed a shut-off valve for the heater line. I am going to try to pump more and see what happens.