91 with weak AC

[NC91Explorer]

91 EB bought new w/ 4 miles. AC has always been weak. At 277K miles, still weak. Been converted to R134 and the results are the same as with R12. Blows fairly cold but not quite the results I get from other vehicles. I read in the forum where 93 AC parts could be placed on 91 and 92s to help the AC blow 5 to 10 degrees colder but could not find where the part was listed. What part makes the AC colder on 91s?

 

[CDW6212R]

Welcome, and there is a heater hose valve on later 1st gen's that is not on your 91 Explorer. The valve mounts along the front right of the engine(water pump), and operates by vacuum.

I don't know if that is the magic part which others have referred to.

By the way, I have a 93 Explorer which I am redesigning. I am about to pull the body off. I will not be using the 93 4x4 chassis, nor the AC system. I have a 99 4x4 donor vehicle which I am replacing the chassis with.

Would you be interested in the 93 AC system? It works fine, it has since I bought it. I have the 99 system intact off vehicle ready to reinstall. I bet that the 93 AC system would also come off intact. The 99 parts probably weigh 40 pounds, they include the firewall box, lines, compressor, and evaporator.

Try the vacuum switch, or start over with something like I have. Good luck,

 

[NC91Explorer]

Thanks for your reply. Makes sense that if hot water is near the AC unit, that would limit the ACs ability to cool down. Trying to get at least 300K on the Explorer but I don't want to go to that extreme of a wholesale change out. My hope was that a particular part that would easily retrofit to my system could make a significant change in how cold the air blows. If the value operates by vacuum, how is it controlled? Is the HVAC controls different on a 93 than on a 91?

 

[CDW6212R]

Run a search for that or those threads. I didn't ever read one, but I have read of others referring to them. Use terms like "AC", "colder", "vacuum", and/or "control".

For general best maintenance, for a keeper vehicle; find a trusted AC shop. Ask them to help you to acquire and install aftermarket quick connect locks, and O-rings. Ford has for many years used quick connection fittings in AC lines. The O-rings do wear out, especially with vibration, and then they leak. To install the O-rings, the system has to be opened, so a shop is needed to remove the freon, R&R the parts, and refill the system. It is an excellent way to be sure that you have the exact amount of freon and oil in the system. Regards,

 

[NC91Explorer]

I went to Advance Auto and got the parts guy to look up a heater control valve for a 94 Exp. He had it in stock for under 20 bucks so I bought it. I also bought some heater hose clamps and some vacuum tubing. I placed the new value about 6 inches away from the firewall, cut the heater hoses and ran the vacuum tubing throught the firewall and spliced into the vacuum line for the Max Air value located just behind the glove box. Now when the HVAC control is set to max air, it now longer circulates hot water in the heater coil because the heater control value sends the hot water back into the engine instead. Now the AC blows about 10 degrees colder and works like it should have since day one. Having had the Exploere since new, this is best the AC has ever been.

Total time spent on conversion about 1.5 hours including letting it cool down to drain the antifreeze before cutting heater hoses.

I had set my goal mileage to 300K, but just might keep on going for 350K plus since the AC is good and cold now.

Thanks to all that posted with suggestions.

 

[msmith65]

I'm doing the same thing this weekend. However, pushing a vacuum line through the firewall is a task I'd like to avoid.

Anyone know whether there's a vacuum line on the engine side of the firewall that would do the trick?
_________________

Edit: Never mind. Found a diagram at Autozone.com that says the switch-activated line is only on the dashboard side of the firewall.

 

[Maniak]

You need a vacuum line that is controlled by the a/c controls.. Otherwise you might as well just loop the heater hoses so they don't go through the heater core. Thats bascially what you would be doing if you connected the heater control valve to engine vacuum (constant vacuum).

On the passenger side, firewall (near the a/c box), at the bottom there is a rubber gromit (sp?) that wires go through.. Its pretty easy to put a slice in the rubber and run the line through it.

~Mark

 

[ma96782]

You might consider what this person had to say:

i have a 92 that i converted and hears a few thing to watch out for.

ensure the right fan clutch is in place. there are standard duty and heavy duty fan clutches. vehicles with an automatic transmission or AC from the factory came with and must use the heavy duty clutch. the heavy duty version provides much more lockup but costs over twice as much as the standard duty and so people tend to cheap out on these.

the blend doors all around suck on these vehicles, none of them(there are at least 3) are reliable. on mine the blend door that switches from PANEL and MAX/AC(recirc) is very unreliable. it will always disengage fine but won't re-engage. the vacuum motor behind the gloves box works as it should but when i hit a good pothole on the right side i can hear the recirc door snap shut and get louder and colder.

ac performance wasn't very good from the factory on 91-93. the heater core conducts a lot of heat into the surrounding area and the condensor seals aren't very air tight, air can go around the condensor before getting sucked into the rad and shroud. ford had a TSB on this issue..
.
.
A/C - Poor Performance
Article No.
97-16-12

08/04/97

AIR CONDITIONING - POOR PERFORMANCE - INSUFFICIENT AIR FLOW THROUGH CONDENSER
LIGHT TRUCK:
1991-93 EXPLORER

This TSB article is being republished in its entirety to update the Service Procedure.
ISSUE:
Substandard A/C performance may occur when the A/C system seems to be functioning properly. This may be caused by excessive heat pickup from the heater core and/or insufficient air flow through the condenser.

ACTION:
Verify proper A/C operation by following the diagnosis and repair procedures found in Section 12 of the appropriate Explorer Service Manual. If the A/C system does not function properly, make the necessary repairs and re-evaluate the A/C system. If the A/C system still does not operate properly (e.g., poor performance), install the condenser seals and water shutoff valve as outlined in this Service Procedure.

the parts for this TSB were fitted from the factory on 94s, you can score them from a junkyard. what i did was getting some thick open cell foam used to seal window A/Cs and some ducktape, i then cut it up and sealed around the condensor. it seemed to lower my high side pressure some. i'm not worrying about the heater core but if i really need the cooling i have a double sided hose barb handy to bypass it. don't just block it off, coolent is supose to circulate thru there for some reason.

from the factory it has a red oriface tube, .062 i believe, i've heard replacing it with a blue one, .067 i heard may help but that could also just be hearsay. in fact i'm not even sure those sizes are right.

the thermostatic switch on the accumulator is adjustable. i got a new one and it came preset around 28 PSI. i turned the screw in the center of the connector counter clockwise until it open at 21 PSI, that seemed to help.

So, seal up the Evaporater box seam with foam, add the heater control valve (from a '94 Explorer), take the vacuum from the correct source, check low pressure switch operation and BTW my '94 uses a blue orifice tube. Operating pressures and R-134a capacity and oil are your guess for your vehicle (AS A COMPARISION my '94 Explorer calls for: a low side at 22-50 psi and high side at 160-250 psi, 36 oz. R-134a, and 7 oz oil)

Aloha, Mark

 

[msmith65]

Thanks, Mark -- that's great info to have.

I just installed a heater-control valve. (My '93 didn't have one.) A previous owner apparently had the condenser sealed, so I didn't have to do that.

The valve is not difficult to install. The challenge was getting a hard plastic vacuum line through the firewall. Here's how it went:

I cut the heater hoses where they run next to the evaporator. It's really the only place to do it without all kinds of parts-pulling.

Here's a close-up view of the valve, which I got from NAPA for just under $30.

You will need four clamps. My mistake was in cutting about an inch out of each line, thinking the valve would take up the slack. You'll actually need that extra inch because the hoses will be offset (upward-downward) by the valve. So don't cut any extra off.

Close-up on the vacuum-diaphragm part of the valve. See the hard, white, plastic line (sorry, out of focus)? That's the last part you'll connect when you're done.

Here's where I took the glove box off to access the MAX AC vacuum diaphragm. (Turns out I didn't need to remove the door, but it helps to show you what I'm talking about.) The black strip with the holes is where the glove box hinge was attached. The silver part is what moves when you switch to MAX AC. Its vacuum diaphragm is the round black part just below. At the bottom of that is the vacuum fitting you'll need to tap.

Here was the difficult part. The hard, white plastic line needed to go through the firewall right where you see it below. (You can also see it toward the bottom of the picture above.) Trouble is, it's a tight fit through a thick grommet and there's gooey sealant inside the grommet.

First I pushed an awl through and wiggled it to make a hole. Then I sliced the plastic line at an angle and slicked up the very end with silicone spray (not too much: your fingers will slip) and pushed it through, just firmly enough not to bend the line. On the third try, it came out on the firewall side just below the new valve. (The first two tries, I couldn't find where it was coming out!)

I got a black plastic tee at a hardware store and used some 1/8" ID clear hose to join it up to the new plastic line, and to the diaphragm under the dash. The amber fitting on the right is what originally plugged into the diaphragm. I thought it easier to use the clear hose to join the diaphragm to the tee, then hook it all up as shown.

A piece of clear hose works well to join the hard plastic line to the valve diaphragm under the hood.

I'll see how it goes. In Dallas, we need all the AC we can get!

 

[msmith65]

Save your money. This mod made no difference in vent temperature.

 

[shamaal]

My experience in a 91 Navajo is literally a 10 degree difference in temperature in the driveway standing still.

By switching MAX A/C in waiting five minutes and measuring the temp at the vents, then switching it out and waiting five minutes there is a measured ten degree difference. I have repeated this twice with the same effect. Maybe the 91s were plumbed different. You have verified that the plunger engages and disengages as you switch the Max A/C in and out?

I expect at speed the difference may be less, but at a standstill in stop and go traffic the temperature is noticeably cooler.

That's my experience.

 

[Maniak]

This mode made a difference on our '92 X. I did this mod a few years ago and have since also done it on an '88 f-150. It made a huge difference there also.

I did my testing with the doors open, a/c on max (so I could keep the input air temp the same on my test). I had between a 5 and 10 degree difference between max a/c with the mod and normal ac.

You also need to test it on max a/c first, then normal a/c.. Otherwise you will have to wait for the vent temp to drop since you already have hot water in the heater core.

~Mark

 

[msmith65]

I tested it apples-to-apples: On MAX AC after a 10-minute run-in each way, and I parked in the shade before starting both times so the heat load was the same.

For one run, I disconnected (and plugged) the line going to the heater-control valve. For the other, I reconnected it. So each way, the only variable was whether the heater core had hot water flowing through it.

Minimum center vent temp: 49 degrees, each test.

 

[Maniak]

Wow, I get close to those temps (low 50's) at max a/c at idle.. when its 90F outside..

I seem to get 40-50 degree temp drops from outside temp to inside temp.

The only odd things I'm running (other than r-134) is a variable oriface tube and the heater control valve.

~Mark

 

[The Man Truck]

Max A/C

Well I just got done doing this and I have to say I am definitely glad I did. I havent really taken it on a long enough drive to really tell a huge difference while driveing but definitely gets colder faster and I noticed that it was colder at stand still.