97 Expy with 5.4L, rear air

Well gotta love summer. I think all is well with my Expy and wham the A/C is blowing different temperatures. I have not driven the vehicle for two weeks and this weekend was a good test as the temps were pretty warm/hot here in the midwest. I've kept the setting on max air and on full cold and this is what happened:

Friday:
5 pm: Vehicle has been sitting, turn on A/C on max cold, drive 10 miles - temp only drops to 70*

7 pm: Drive home, another 10 miles back, after car has been sitting for two hours - A/C drops to 60* this time

Saturday
11 am: Get in it drive 5 min to hardware store - temp drops to 50*

12 pm: drive back from hardware store - temp only gets to 60*

1 pm: drive it 20 miles to graduation party for cousin - temp drops to 40*

3pm: off to another part - temp again to 50*

7pm: temp down in mid 50*


Now each time the I drove, the A/C blew at that temperature and stayed there. I know its not the blend door as all winter long the heat was fine and would change temperature as I moved the control.

I also changed the main temperature control switch back in March.

Lastly, I called my A/C repair guy, told him what was happening and he said: "it sounds like the control" - that's it. I told him I gotta get it working cause I'm going on a road trip in a week and a half!

What do you all think?

 

Have you checked the temp on the rear air as well as the front? On our Navigator- the rear air is cold-always in the mid 40's or lower output temp, but if I don't allow the blend door time to close before hitting it with full speed from the blower fan, then it'll be in the mid 60's for output temp. Seems like the pressure of the blower keeps the blend door from closing. This is just my theory-I haven't had time to teat into it to verify this. I do know if I start the front blower on low until the output air is nice and cold,then speed up the blower-the output temp matches the rear air system's output temp. I'm pretty sure it's just a weak/defective blend door actuator motor.
JL

 

No I have not checked the rear air temp - never crossed my mind. I will drive it again tonight to see. In addition, I will try what you suggest and keep the A/C on low and then kick it up to max blower speed. My other concern is if the mechanic I'm taking it to, and let's say for fun it is the motor, I wonder if I should look into having the blend-door replaced as well. I'd hate to couple this new motor to a 10 yr old door and have it crack on me. Overall, I'm hoping the dash won't have to be removed for this process.

 

I'm pretty sure I can get the motor out without removing the dash, but the blend door itself...not gonna happen. The dash has to come out for that.
JL

 

JL,

You are on to something with that blend door motor theory. I did a small test for you and took my truck out for another 10 mile spin. Turned on car with AC totally off and in max cold position. Once I put it in drive, I turned the AC on to MAX AC and left the blower speed on 1. Sure enough, the temp dropped down into the 40*-45* range. Once I turned the blower up to 4 (max), the temp rose to 50*-52*. Then I turned it back down to speed 1, temp dropped (within one minute) to 40*-42* again. Once it dropped down and stayed consistent, I turned the speed to 4 and the temp went up to 52*. Did this 3 times with the same result.

Temperature got colder at lower speeds, warmer at full.

Thanks,
Tom

PS - I know I could do the motor myself but I don't think the AC is getting cold enough so I at least want that checked out. The 01 F-150 I was in got down to 38*.

 

Thought I'd do a follow up. Got my truck back today and my repair guy told me I was low on refrigerant which was causing the variations in temperature. It's not blowing a consistent 40* on low and up to 45* when on full speed. It wasn't low by a lot because the temp still dropped pretty low when blowing slow. He said if it starts to blow warm anytime soon the next step is the blend door and/or actuator. I told him if we go that far, I'm replacing both at the same time due to the one possibly cracking and I'm going to have the aftermarket metal blend door installed and be done with it once and for all.

Thanks for the help, especially to JL for his posts.

Tom