AC Blows Cold Around Town But Hot On the Interstate

[BUXTER]

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.

HCV is bad.... 3rd Post this Thread over 2 weeks ago....

IIRC Heater Control Valve defaults to Open & goes to Closed via its Vac Diaphragm when AC is max cold - I'd check HCV Diaphragm first - U can watch HCV Close when selecting Cold Air in idle (Hi Vac situation) - Now whether its HCV or Vac Switch leaking in Low Vac situation (Hi speed) is the question - BTW U can throw a Tie Wrap on HCV & hold that puppy CLOSED.

BUXTER, April 15, 2019 Edit Delete Report Top of Page

 

[koda2000]

My Post over 2 weeks ago....

IIRC Heater Control Valve defaults to Open & goes to Closed via its Vac Diaphragm when AC is max cold - I'd check HCV Diaphragm first - U can watch HCV Close when selecting Cold Air in idle (Hi Vac situation) - Now whether its HCV or Vac Switch leaking in Low Vac situation (Hi speed) is the question - BTW U can throw a Tie Wrap on HCV & hold that puppy CLOSED.

BUXTER, April 15, 2019 Edit Delete Report Top of Page

Agreed and I've learned that even a tiny vacuum leak can screw with your HVAC control, but if this the case at the same time the OP looses A/C at higher speeds he'd also have his air flow default to the defroster vents.

 

[BUXTER]

Agreed and I've learned that even a tiny vacuum leak can screw with your HVAC control, but if this the case at the same time the OP looses A/C at higher speeds he'd also have his air flow default to the defroster vents.

Yes I hv a couple Fords & Lincolns that do that & of course Vac lowest at Hi Speed - OP said he tried my suggestion hence my conclusion that HCV internals are bad IF he made sure HCV was Closed & still had Heat.

 

[koda2000]

Yes I hv a couple Fords & Lincolns that do that & of course Vac lowest at Hi Speed - OP said he tried my suggestion hence my conclusion that HCV internals are bad IF he made sure HCV was Closed & still had Heat.

If the HCV internals are bad (valve not stopping water flow when closed) perhaps he should try just looping the heater hoses at the firewall (5/8" ID hose and a couple of 5/8" plastic unions. If he tries that (he won't need heat for another 5 months in GA anyway) he will have eliminated all possibilities of heat getting into the HVAC system.

Running on A/C MAX not only shuts the HCV, but it also closes the fresh air intake (recirculates cabin air) for maximum cooling).

 

[GLOCKer]

Okay. I'm frustrated because you's think a shop would have been able to see this. So it could appear to be working but not actually be working?

I am very frustrated.

I just called them and they said they haven't been able to figure it out. They said the blend door and actuator are working. They have left the heater core bypassed.

I'm going to call them back and ask them to un-bypass the heater core, pick the Explorer up, and try to work the problem next week.

 

[GLOCKer]

So I just called back, and this time spoke to the owner of the shop. (The young lady who answers the phone is who I spoke with before).

"We replaced you heater control valve. It's probably a blend door and your dash would have to come out. We really don't want to mess with that. You don't want to mess with that. It's going to be six to eight hours of labor. Something is wrong in the heater control box."

I am so damn frustrated right now. I'm paying them and getting the Explorer back in whatever condition it is in. Well, that's with the heater by-passed and the AC blowing freezing cold, but with no heat until, "Seriously, just bring it back in October and we'll put the hose back to the heater core and you'll have heat when it starts to get cold."

I don't know where to go with this. I tested my blend door actuator, and it worked. I've never heard any bad sounds, as if something was broken or flapping around, from the blend door.

I guess I'm going to cut open the blend door box and see if it's actually broken or not! I don't have a clue what to do after I cut it open other than hope that I'm not cutting open a box with a broken blend door. Because if I cut it open and the blend door is fine, I haven't chased down the problem and I've cut up a perfectly good box!

ARGHHHHHHH

 

[BUXTER]

I give the shop BIG KUDOS for not tearing into the AC System like 3 pages of this Thread was ready to do.

 

[RickOTR]

If you need to replace the blend door inside the heater core housing, you can pull the Evapotator housing to get to the blend door. Much easier than removing the dash IMO. Just play with it and it will eventually come out. That's how I replaced mine in about three hours. This also gives you the chance to clean out all the leaves and other stuff that built up around the Evaporator core all those years. You wouldn't believe what I dug out of mine, NASTY! Here's the link for the blend door I used to fix my X. https://www.amazon.com/Dorman-902-221-Blend-Door-Repair/dp/B005VTT3JY

 

[koda2000]

@GLOCKer - Many posts ago (in another of your threads) I believe I suggested you remove the crescent shaped gear from your blend door actuator and install it on top of your blend door to operate it manually. Doing this would allow you to check the operation of the blend door without cutting into the heater box. or taking stuff apart. You should be able to rotate the crescent gear through it's full range of motion (approx 1/4 turn) and feel when the blend door is completely open and completely closed. You can also feel when it hits it's heater box's seals.

Did the shop change the HVC or just bypass it? That wasn't clear.

When my daughter's 2000 Mountaineer's stopped cooling one spring, I operated her blend door manually (using the blend door actuator's crescent gear attached to a piece of baling wire) for 2 years (open for winter/closed for summer). About a month ago I finally installed a working replacement blend door actuator I constructed from parts I had laying around and it's now back to normal operation.

If you want I'll mail you an old crescent gear to use. It's even modified to accept a piece of bailing wire so it can be tied off in either position.

I know this whole A/C issue seems very complicated and has you head spinning, but honestly it a pretty simple system to understand.

 

[masospaghetti]

If the blend door is bad, it can be fixed without removing the dash. You can cut an access hole in the bottom of the box, if you cut in the right place, the blend door will fall out and you can put a new one in. RTV it shut.

If for some reason the heater box needs to be removed, this can be done with loosening the dash (but not entirely removing it). I was prepared to do this when I thought I had a heater core leak. Looks like this can be done in a few hours. It's not a trivial job but its not 8 hours worth of shop labor.

Is the system cooling at all and just not meeting the spec temperatures? How bad is it?

Also remember that our trucks have a mechanical fan that isn't directly controlled by the air conditioner so the cooling performance may not be "as good" as some newer vehicles with electric fans, especially at engine idle while stationary. This especially if your fan clutch is bad or weak. The fan is controlled entirely off of the temperature of the coolant at the water pump.

If the system cools but not optimally, "in my opinion" this is a good chance to get some HVAC equipment and work on it yourself. You'll learn a bunch in the process, save a bundle, and get some neat new tools for the next project vehicle.

 

[koda2000]

If the blend door is bad, it can be fixed without removing the dash. You can cut an access hole in the bottom of the box, if you cut in the right place, the blend door will fall out and you can put a new one in. RTV it shut.

If for some reason the heater box needs to be removed, this can be done with loosening the dash (but not entirely removing it). I was prepared to do this when I thought I had a heater core leak. Looks like this can be done in a few hours. It's not a trivial job but its not 8 hours worth of shop labor.

Is the system cooling at all and just not meeting the spec temperatures? How bad is it?

Also remember that our trucks have a mechanical fan that isn't directly controlled by the air conditioner so the cooling performance may not be "as good" as some newer vehicles with electric fans, especially at engine idle while stationary. This especially if your fan clutch is bad or weak. The fan is controlled entirely off of the temperature of the coolant at the water pump.

If the system cools but not optimally, "in my opinion" this is a good chance to get some HVAC equipment and work on it yourself. You'll learn a bunch in the process, save a bundle, and get some neat new tools for the next project vehicle.

If I'm understanding the OP's last post, the A/C is now working great with the HCV bypassed (heater core not connected). Was the $700 worth of work performed necessary? IDK. At least it should now give the OP many years of trouble-free operation now. Maybe he'll figure out the HVC/blend door issue before winter.

 

[RickOTR]

I can't stress enough to remove the evaporator core housing and cleaning that thing out. Years of collecting, dirt, leaves, and other foreign material in there really clogs the cooling fins. This is what was happening to my X when I got it on the highway. No cooling, nothing but hot are. When I slowed down, I had plenty of cold air coming out of the vents.

 

[koda2000]

I can't stress enough to remove the evaporator core housing and cleaning that thing out. Years of collecting, dirt, leaves, and other foreign material in there really clogs the cooling fins. This is what was happening to my X when I got it on the highway. No cooling, nothing but hot are. When I slowed down, I had plenty of cold air coming out of the vents.

Can't hurt. Also check/clean your condenser to make sure it's not full of bugs and leaves.

You'll know when your fan clutch is not working properly when it cools okay while moving but warms up when stopped in traffic.

 

[RickOTR]

Here's a link on removing evap housing
How to: Evaporator core replacement.

And here's a video on what my mine looked like after removing it.


Good point on cleaning out the condensor too...

 

[GLOCKer]

Okay, I wont be able to confirm all of this until I get my hands on the truck, but as I understand it, this is where I stand:

• The AC blows ICE cold now. With the heater core bypassed.

• It SOUNDS like the heater core has been bypassed entirely. As in physically disconnected and the hot water is being returned...

• According to the owner of the garage, a NEW HCV has been installed as they suspected that, but it made no difference. (He said I'm not even being charged for that.)

• He said at this point, it's something behind the dash. A "a relay or one of the blend doors," is what the owner of the shop said. He went on to explain it wasn't worth anybody's time or money to fix it.

So I'm guessing, as suggested, I need to look at the blend door. I'm familiar with the kit from Doorman that allows you to cut into the box to effect the repair, and I'm not opposed to that. @koda2000 , I am very heavily leaning towards taking you up on your offer to borrow your crescent gear to rig up the blend door to test. In fact, I think I will do this. I will gladly compensate you for the use of the gear and postage, and return it to you.

I really don't like band-aids on stuff to fix problems. And keeping this thing with the heater bypassed until late fall just doesn't seem like a viable solution to me. I want to see this fixed (for a reasonable cost). I want to be driving this thing 100,000 miles from now and I don't want to own a heap of junk that's become a collection of band-aided parts and systems.

Thank you guys for all of your help and suggestions.

 

[koda2000]

@GLOCKer - PM me your address and I'll mail the crescent gear to you. You can keep it, I have several others and no compensation is necessary. Other's here have helped me with parts in the past, so I'll just pay it forward. I'm usually not one for band aide fixes either, but sometimes it's good enough for a temporary solution for expedience's sake. I know I never use my heat from May - end October and rarely use A/C (other than for defrost, which still works whether the blend door is open or closed) from Nov - April.

There is only one "blend door". All it does is blend hot air from the heater core with cold air by opening a specific amount as dictated by the EATC temp setting. I can understand why the A/C shop owner told you fixing a broken blend door wouldn't be worth it, but that's because his flat rate book tells him it's an 8 hour job. He's no doubt unaware of the short cuts that are known to the collective members of this forum. I'd say you could replace the blend door in about 45 mins by cutting the heater box. The procedure is outlined in the "Useful Threads" section.

 

[GLOCKer]

@GLOCKer - PM me your address and I'll mail the crescent gear to you. You can keep it, I have several others and no compensation is necessary. Other's here have helped me with parts in the past, so I'll just pay it forward. I'm usually not one for band aide fixes either, but sometimes it's good enough for a temporary solution for expedience's sake. I know I never use my heat from May - end October and rarely use A/C (other than for defrost, which still works whether the blend door is open or closed) from Nov - April.

There is only one "blend door". All it does is blend hot air from the heater core with cold air by opening a specific amount as dictated by the EATC temp setting. I can understand why the A/C shop owner told you fixing a broken blend door wouldn't be worth it, but that's because his flat rate book tells him it's an 8 hour job. He's no doubt unaware of the short cuts that are known to the collective members of this forum. I'd say you could replace the blend door in about 45 mins by cutting the heater box. The procedure is outlined in the "Useful Threads" section.

Thank you! I'm about to send you a PM.

 

[koda2000]

Thank you! I'm about to send you a PM.

No problem. I'll try to get it out to you w/in the next couple of days.

 

[GLOCKer]

Today I walked 2 miles in the heat to the mechanic and I got the truck back; it was $750.05 out the door. The way the invoice breaks down, it makes sense between the labor hours and parts. In fact, I'm pretty sure they softened the hours.

They also installed a new belt too. There is a new accumulator under the hood along with a new heater control valve. And a shiny new compressor! In the attached picture, you can see how they bypassed the heater.

One thing I was surprised with is how much quieter the Explorer idles. It was pretty quiet before, but now it's VERY quiet. In fact, if not for the header leaking it would probably just be fan noise!

@koda2000 is sending me a small part to help troubleshoot the blend door. At this point I will be glad to cut open my box to change out the blend door if it's broken! I don't like band-aides and for some reason, I've been a little obsessed with getting every individual system on this old turd back to working properly.

 

[CDW6212R]

Very good. You've got AC again and it's cold, enjoy that. You are caring of your cars, that's great.

Let me lend you mine(swap) for a couple of months, and you can work out a few little bugs it has. I haven't had time to do anything really with mine, I just drive it and work it every day, approaching 224k miles now.