AC Blows Cold Around Town But Hot On the Interstate

[RandomNerd2000]

I'm late here, but since I've done this work on my trucks before, I'm going to just type out a good summary of what causes this. What you have is a low pressure situation on the low side of the refrigeration system, on the interstate, which has been stated, The common causes for that are the low pressure switch isn't cycling the compressor off on the interstate, since that has to happen, if the pressure gets too low on the low side, icing results. Freon might be low, that's common on older vehicles, even if they don't leak, since some part of the system is always under pressure, and there are rubber seals, which never are absolute seals. Third cause, which with a proper set of manifold gauges will be apparent, is a clogged or broken orifice.

Please note, if the orifice is restricted, you have something in the system that caused that, which is almost always a failing compressor, a good set of manifold gauges that hook to both service ports will show that issue easily. I'd also hook a good set of gauges up, because like many have said, the can gauge isn't even remotely accurate in my experiences.

 

[GLOCKer]

Could the low side having too high of a pressure cause the same issue?

And could too high of a pressure be caused by the clogged orifice tube?

I'm hoping it's a bad dryer canister causing a clogged orifice tube and not a bad compressor!

 

[GLOCKer]

It's at a shop now and the final verdict is a bad compressor. Ouch.

 

[BUXTER]

for God's sake put a new Filter Dryer on it too as I'm sure ur reputable AC guy has advised ~!

 

[Dono]

And the orifice tube. it will be catching the teflon from the compressor.
I did mine myself when I found teflon in my orifice tube. Upon advice I replaced 4 of 5 major components.
Compressor, Dryer, orifice tube, and condenser. You will need to add an ounce or two of oil when replacing all these items (The new compressor probably has some, so you will need to read up on whats required).
It's actually pretty easy to do, the only real guess work ended up being the oil.

I'm sure you could have a shop evacuate and fill the system after you have replaced the hard parts. With the cost of labour, I just found a great deal on a vacuum pump and gauges and did this myself. I used RedTek refrigerant as its readily available in Canada. It works really well.
I have done the job a few times now on other vehicles, so I'm deep in to the 'free' zone on the tools.

 

[GLOCKer]

I'm assuming (bad thing to do, I know) that the shop is going to refresh the whole system. I've seen most "kits" come with the dryer, orifice tube, oil, and o-rings. The cost is going to be around $700 all said and done.

 

[GLOCKer]

UH OH! Not good!

I called the shop today just to get a sense of when the Explorer is going to be done so I can make plans for next week. The nice young lady on the phone told me they weren't happy with how it was cooling, but that it'd probably be another 45 minutes for them to figure it out, and then I could pick it up. SWEET!!!

So after a couple of hours, I didn't hear back from the shop. My wife and I decided to knock out the grocery shopping and we hit the road. On the way back from the store, we were driving right by the shop; so we stopped in to check it out.

They said it is cooling but not very well and they are STILL trying to figure it out. I got this much from them (the mechanic that is actually working on it was walking into the bathroom as I was walking up to the shop); it has a new compressor with a "bunch of new stuff that came with it." They also pulled the orifice tube (I'm sure the compressor came with a new one) and flushed out the system. Other than that, she didn't know what to say and offered to let me wait to talk to the mechanic. We had a bunch of meat in the car for tomorrow so I had to jet and couldn't wait.

I'm a little concerned.

 

[Dono]

They will figure it out. Its what they do. Don't stress.

 

[GLOCKer]

Good news AND bad news. The shop called me this morning to tell me they bypassed the heater core and that when they did that, the AC was blowing a consistent 36 degrees.

 

[Dono]

Theres a solenoid that shuts off coolant flow to the heater core when 'max ac' is selected. start by looking there, as hat solenoid may not be working.

 

[koda2000]

When our 2000 Mountaineer's A/C stopped blowing cold one spring it turned out to be blend door related. Wasn't the blend door itself, it was the actuator that failed. Before that, the the EATC unit had failed and I replaced it with a used one from eBay for $50 . Other than the two failures, which occurred about 4-6 months apart, the A/C's been working fine since. The truck now has 265,000 miles+ on its all-original A/C parts and I've never had to add refrigerant to it in the 90,000 miles+/8 years I've owned it. I did replace the A/C clutch when I first got it (because it rattled).

I'd be pissed at your A/C guy for not diagnosing the problem correctly (sounds like they didn't even try to diagnose it). I know a fair bit about A/C systems and how they work and a lot about Gen II Explorers/Mountaineers. I diagnosed both my A/C issues correctly w/in 30 minutes. From the beginning I couldn't understand how your compressor could be the problem. So now they emptied your wallet of at least $700 and will probably want more money to replace a $17 actuator or install a reman'd $100 EATC unit. This is exactly why I do my own diagnostics and repairs. It's not that I sometimes don't have the time or desire to work on my own vehicles, it's just that almost every time I've paid someone else to fix something on my cars/trucks they've screwed me charging me for unnecessary labor & parts because they're either thieves or incompetent.

I'd like to know exactly how your A/C shop came to conclusion that your compressor was bad and I'd demand a major reduction on your bill.

 

[CDW6212R]

I agree, it could be that there was only one problem, the HVC or the blend door(or actuator for it). Start with the HCV, that's easy to see if it's working, and minor to replace it if you suspect it.

 

[Dono]

Stuff like this is why I prefer to live the pain of fixing stuff myself.
It seems that when life gets too busy (Or I'm just too frustrated) and take my vehicle somewhere they either can't fix it, mis-diagnose, or just plain screw it up.

A good mechanic is worth their weight in gold.

Sorry your going thru this. Lets hope that at least the orifice tube was full of teflon, showing the compressor was actually on its way out.

I just don't get that they had to bypass the heater core with that valve there that can shut off the coolant flow to the heater core though. Don't most vehicles have a same sort of system when you switch to max ac? Wouldn't the shop know this?

 

[GLOCKer]

If the vacuum servos (I don't know how to correctly refer to them) go out in the EATC, would the EATC throw a fault during a diagnostic?

 

[Dono]

I don't think so.
The solenoid can be watched in operation though.
2000 FORD EXPLORER 5.0L V8 Heater Valve | RockAuto
It's located under the hood right in front of the heater box up top.
There should be a vacuum line hooked up to it, and you should see the solenoid pull when you switch to 'max ac'. Whwn the solenoid pulls, it's supposed to shut coolant flow off to the heater core (That's why I'm not sure they needed to bypass the heater core).

I'm betting the guys have the original issue fixed, but are trying to get the temp down to spec at the vent.

You should be able to to test the blend door by just changing the heat temperature on the etac to hot, then something cooler. If the temperature isn't changing you have a problem. with etac/blend door assembly.

 

[GLOCKer]

I don't think so.
The solenoid can be watched in operation though.
2000 FORD EXPLORER 5.0L V8 Heater Valve | RockAuto
It's located under the hood right in front of the heater box up top.
There should be a vacuum line hooked up to it, and you should see the solenoid pull when you switch to 'max ac'. Whwn the solenoid pulls, it's supposed to shut coolant flow off to the heater core (That's why I'm not sure they needed to bypass the heater core).

I'm betting the guys have the original issue fixed, but are trying to get the temp down to spec at the vent.

You should be able to to test the blend door by just changing the heat temperature on the etac to hot, then something cooler. If the temperature isn't changing you have a problem. with etac/blend door assembly.

So I've messed with the heat and AC and visually confirmed the HCV looks to be working.

What I'm talking about is inside of the EATC module. I'm sorry abou the small picture, but I'm talking about these suckers here:

If the seals go bad in them, will the EATC throw a code on diagnostic?

 

[Dono]

I haven't had to dig in to my etac unit. Luckily.

 

[GLOCKer]

I haven't had to dig in to my etac unit. Luckily.

I hope I don't have to, too! I think if mine was going out I'd just hit up a junkyard!

 

[koda2000]

There is an EATC self diagnostic test you can do, though it doesn't catch everything. You initiate it with hitting 2 buttons at once and then a 3rd w/in 5 seconds. (Google it). The O-rings going bad and leaking effects vacuum related functions/controls. There's also a small relay that controls the compressor. Both issues have been reported here. I wouldn't quite say that they are common problems, but there have been a number of threads on EATC problems/fixes.

I don't think so.
The solenoid can be watched in operation though.
2000 FORD EXPLORER 5.0L V8 Heater Valve | RockAuto
It's located under the hood right in front of the heater box up top.
There should be a vacuum line hooked up to it, and you should see the solenoid pull when you switch to 'max ac'. Whwn the solenoid pulls, it's supposed to shut coolant flow off to the heater core (That's why I'm not sure they needed to bypass the heater core).

I'm betting the guys have the original issue fixed, but are trying to get the temp down to spec at the vent.

You should be able to to test the blend door by just changing the heat temperature on the etac to hot, then something cooler. If the temperature isn't changing you have a problem. with etac/blend door assembly.

@Dono - What is your definition of a solenoid? It sounds like you;re maybe talking about the blend door actuator, but it's not located under the hood, is not vacuum controlled and the heater box isn't under the hood either. The blower fan and it's module are located in the area you're describing, but they're not vacuum controlled. There are a number of vacuum motors controlled by the EATC. They control air direction and are all located under the dash. Solenoids are electrically controlled electrical switching devices.

Sounds like maybe you're talking about the "heater control valve/HCV", which is located in the area you're talking about and is vacuum controlled. It turns off the hot water supply to the heater core. Note: Not all years have this valve and on some models it's not located in this area. As far as I know, the HVC on my Explorers only shuts off the hot water to the heater core when you're on A/C MAX. If the blend door is working properly it's closed unless you run A/C MAX with a temp setting of something over 60 degrees. If @GLOCKer is getting heat blended in with his A/C when it's not called for (and if there's nothing wrong with his A/C system) there must be an EATC, blend door/blend door actuator related problem. In a battle between heat and A/C, heat wins.

 

[Dono]

@Koda , thats exactly what I am talking about. See the picture link I posted to rock auto.

If you read above, the op knew exactly what I was talking about and already tested it.