No air from rear vents

[drokmofo]

1st off, if this is redundant plz direct me to the thread. 2007 EL 5.4 179,*** miles. Got in to go across town yesterday and nothing came out of rear vents for the kids. No air at all, hot or cold. For the past couple months the air has taken a while to cool down if it does at all. I am assuming there is a freon leak and it is low. I haven't checked anything yet. After reading some info other from other sites I am thinking it could be either a fuse, a relay, an actuator or 2, or the rear blower motor. If the freon is low will the system shut down the rear? Any and all advice is appreciated. Thx in advance.

 

[07navi]

The "freon" is the same for front and back.

 

[drokmofo]

Thx, I was pretty sure about that. That is why I asked if the refrigerant got low, would it not run the rear at all. Keep the ideas coming plz!

 

[07navi]

Thx, I was pretty sure about that. That is why I asked if the refrigerant got low, would it not run the rear at all. Keep the ideas coming plz!

It all runs the same. You need some cheap gauges and to read a few youtube vids on using it.

 

[drokmofo]

Thx

 

[Hoffy90]

Can you hear the blower motor running? We had a completely clogged ac evaporator that wouldn't allow any air through.

Sent from my Pixel 3 XL using Tapatalk

 

[07navi]

Does the front blow cold? You should have about 35 psi on the low side and about 150 psi on the high side on a 70* day. Gauges are good to have.

 

[drokmofo]

I dont hear the blower motor. Thinking about going to harbor freight and buying a set of gauges. It is 100* here rt now. How would those pressures relate to this temp? Thx again. I'm thinking it is the blower motor. Front takes a while to get sorta kinda cold. Doesnt start out hot, but def not cold.

 

[07navi]

I dont hear the blower motor. Thinking about going to harbor freight and buying a set of gauges. It is 100* here rt now. How would those pressures relate to this temp? Thx again. I'm thinking it is the blower motor. Front takes a while to get sorta kinda cold. Doesn't start out hot, but def not cold.

At 100* your pressures would be more like 45 and 230. The ac's are warmer when it's warmer outside. I taped a little thermostat on my middle vent and it is 20* cooler than outside. Some are 30+- cooler but 20 is plenty for me. You could have a bad blower or evaporator in the rear also. There are other threads in here on that.........do a search.

 

[drokmofo]

Ty

 

[Trainmaster]

If the front is working fine and the rear's not, your Freon's fine. No need for gauges or any of that stuff.

If the rear blower is not blowing you have an electrical problem, probably with the controller, fuse or rear blower motor. If the rear motor's running but you get no airflow you have a blend motor problem or maybe a clogged rear evaporator.

 

[07navi]

If the front is working fine and the rear's not, your Freon's fine. No need for gauges or any of that stuff.

If the rear blower is not blowing you have an electrical problem, probably with the controller, fuse or rear blower motor. If the rear motor's running but you get no airflow you have a blend motor problem or maybe a clogged rear evaporator.

He said the front isn't very cold and we all can use those gauges, especially him right now. Of course cold air won't fix the rear problem but he will need it eventually.

 

[drokmofo]

So, I got into the rear ac compartment and beat the fan motor a couple times with my hand and it kicked on. I can change the speed some by hitting it multiple times. Me caveman. Doesn't sound real smooth but it is flowing again. I'm going to add some r134 and see what the temp does. Going to price out the blower motor locally. Have it in cart on rockauto. I may still buy some gauges or borrow from bro in law....

 

[07navi]

So, I got into the rear ac compartment and beat the fan motor a couple times with my hand and it kicked on. I can change the speed some by hitting it multiple times. Me caveman. Doesn't sound real smooth but it is flowing again. I'm going to add some r134 and see what the temp does. Going to price out the blower motor locally. Have it in cart on rockauto. I may still buy some gauges or borrow from bro in law....

Like I said the gauges won't fix you rear ac problems but they are needed if you are going to maintain your AC system. You would pay more to have someone check it than a pair of gauges would cost plus you wouldn't learn anything. Let us know what your readings are and the ambient temperature.

 

[drokmofo]

I haven't put gauges to it but I did add maybe 16oz r134. Just idling in the driveway the temp got down to 65* at the front vents. The rear blower motor is all over the place with it's output. I put my arm in thru the cupholder tray and bang on it to increase flow. It was 104* today while I was working on this. I will be ordering a new blower motor from rock auto. $75 for a motorcraft blower and $27 for the resistor. Should I get the resistor? Thx for your continued input 07navi

 

[07navi]

I haven't put gauges to it but I did add maybe 16oz r134. Just idling in the driveway the temp got down to 65* at the front vents. The rear blower motor is all over the place with it's output. I put my arm in thru the cupholder tray and bang on it to increase flow. It was 104* today while I was working on this. I will be ordering a new blower motor from rock auto. $75 for a motorcraft blower and $27 for the resistor. Should I get the resistor? Thx for your continued input 07navi

IDK about the resistor, probably not. Wow that's 40* colder than outside, I'm lucky to get it 25* colder at the vents on the freeway. Be careful adding refrigerant without the gauges though, you can slug the compressor and destroy is with too much. At those outside temps your high side will be well over 200.

 

[drokmofo]

I will take your advice with the gauges. Thank you much appreciated.

 

[Trainmaster]

Pull the resistor and make sure a loose connection on it isn't your problem before buying parts.

 

[07navi]

Pull the resistor and make sure a loose connection on it isn't your problem before buying parts.

He beat on it and got it going. Is the resistor attached to the unit? What does it do?

 

[Trainmaster]

I'm not sure where the resistor is on the rear blower. On the front blower it's mounted on the plenum box with the resistor coils in the airflow to cool them. The resistor consists of a series of open resistance windings that are switched in and out of the fan circuit to vary the motor voltage, controlling the speed. Since they get very hot from the current flow, they are not soldered but crimped together. Sometimes the crimps and corrosion get the better of them or the coils split and they open up, responding to the pounding that the OP described.

So if the resistor is anywhere near the rear motor, it should be checked before the motor is assumed to be the culprit. Locate it and fiddle with it to see if the internal connections are intermittent.

For all I know, newer models may be a different design -- electronic stuff that is not plagued by these problems. The last one I've dealt with was in a 2000, and that had conventional windings.

Here's a traditional blower resistor from a 2010 Explorer. The coils project into the plenum. See the crimps? The little semiconductor is a temperature fuse that opens if the thing overheats, as it may if airflow is obstructed.