Hot air blows out of the vents in summer.

[buzzcon]

Hi everyone! Been a while since my last visit!

I have a strange issue. As you know, it's summer. I can be driving my 98 Expedition with the vent blowing air from outside, but every once in a while, it throws hot air right after I hit a decent bump.

Also, late last winter, the front heat would take forever to blow hot. The rear blows hot air just fine. My air conditioning doesn't work either.

The guy who looked at my AC checked the pump and said it seemed fine and he put the system under vacuum and it held vacuum, so no apparent leaks. He told me my issue with the heat was an expensive fix.

Any ideas???

Thanks in advance!!

 

[98EXPnSRQ]

Sounds like the blend door broke. Very common problem. Search on youtube for videos.

 

[buzzcon]

Sounds like the blend door broke. Very common problem. Search on youtube for videos.

Sounds like a solid plan! Just needed a nod in the right direction.

Thanks!

 

[98EXPnSRQ]

I had mine replaced a few years ago. I had a shop with experience to do because you have to pull the entire dash out. Now they have a replacement blend door with a spring loaded post, so you can just cut a big hole in the plenum box and install it that way so you don't have to pull the dash out.

 

[buzzcon]

Are you sure it could be the blend door? As I stated in my OP, it blows cool, but will blow hot air after I hit a bump. The controls are set to cool when that happens.

I was thinking electrical as in the controls etc. I guess it could be the actuator now that I think about it.

 

[stamp11127]

The regular way for replacing the blend door really isn't as bad as people make it. To me the worst part is those little screws for the floor vents - royal pia.
Use a sewing storage kit for the screws and bolts since there is quite a few of them.
Set the front seats all the way back before starting
Once the dash is free just swing it into the passenger seat, you can wedge yourself in if you are a "big ol boy" like myself.
Best tool to have is a portable impact wrench and 1/4" impact socks/bits. They are what make the difference here.

If you are going to change it yourself, consider changing the heater core since it is right there.

 

[98EXPnSRQ]

Are you sure it could be the blend door? As I stated in my OP, it blows cool, but will blow hot air after I hit a bump. The controls are set to cool when that happens.

I was thinking electrical as in the controls etc. I guess it could be the actuator now that I think about it.

You should be able to move the temp knob from hot to cold and see if the motor is turning. The bottom of the blend door goes into the motor. This is where it breaks. When it breaks it can flop around and go from hot to cold as you describe when turning or hitting a bump.

 

[jbanks]

Sounds like blend door to me also. I did the 'cut the box' behind the glovebox method a couple years ago and it still works great.