A/C Issue

[CrawlinTBSS]

i hate dealing with A/C unless its just a nice evac and recharge. diagnosing i suck at...

our landlord has a 04 mercury sable. 3.0L DOHC with a funky issue.

unpon first startup on cooler days/sitting in garage from the nite, the A/C runs and blows cold.Once the car sits outside during the day in the hotter temps ( like last week in the afternoon hitting 100+) the a/c just blows hot air. Dont think the compressor even cycled on.

its been to 3 dealerships and still cant figure it out. anything common with these things ? something getting plugged? bad HP/LP switch?

he brought it by last friday but low n behold it was raining and like 72 that morning so it was working just fine. Nothing is frozen under the hood when its blowing hot either...

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[Dasfinc]

i hate dealing with A/C unless its just a nice evac and recharge. diagnosing i suck at...

our landlord has a 04 mercury sable. 3.0L DOHC with a funky issue.

unpon first startup on cooler days/sitting in garage from the nite, the A/C runs and blows cold.Once the car sits outside during the day in the hotter temps ( like last week in the afternoon hitting 100+) the a/c just blows hot air. Dont think the compressor even cycled on.

its been to 3 dealerships and still cant figure it out. anything common with these things ? something getting plugged? bad HP/LP switch?

he brought it by last friday but low n behold it was raining and like 72 that morning so it was working just fine. Nothing is frozen under the hood when its blowing hot either...

If its blowing HOT air, this could signify that the heater core is having coolant flowing through it and not being by-passed. (Alot of it is magic to me as well, but bear with me)

I think the design is the same for most older fords, there is a vacuum actuated valve that controls the coolant flow to the heater core. *Explorers below*

When I got my explorer it was blowing hot air because the valve didn't have good vacuum (Cracked hard line), so the heater core was always hot within the truck, and in the explorer, the blower motor blows past the A/C system, and THEN the heater core when pushing air into the truck (no mechanical door that forced air to be pushed past the heater core OR the A/C 'radiator' thingy). Replaced the hardline, re-charged the A/C, haven't had a problem since.

I have NO idea how the vacuum system works other than there is a big plastic ball that has Vac off the intake going to it hiding in the fender well, and then another line that goes to the heater core box (not the valve) IIRC. but those stupid hardlines are horrid, as is the rubber 'booties' that i'm sure all expand/contract to a certain degree, and may be affected by the weather.

the hard vac lines and connectors are all very cheap, so it wouldn't be a bad place to start throwing money at it IMO.