Can't figure out these AC problems

[chrisblue23]

Hello all,

I have a 2000 Ford Expedition RWD with the 5.4L in it. It has 232,000 miles on it and it runs just fine like day one. I have been having some weird AC issues these past few months but I haven't figured them out. Now that it is 110+ outside I am wishing I had the AC.

The front blower motor does not work. I tested the voltage going to the blower motor and no matter how much I adjust the dial, it stays at 8.70V. I figured it was the resistor and blower motor. The thing that troubles me is the rear AC vents work just fine but they don't get cold at all and I can hear hissing in the AC lines while it is on. The hissing sound mainly comes from the back of the vehicle and I took a side panel off and I could hear the hissing in the lines. I would understand if the front doesn't work but wouldn't the rear still get cold and work? I am starting to think that the whole EATC system doesn't work and needs replaced. I am wondering where should I start looking? I did the self-diagnostic thing and nothing came up so that was of no help. Thank you so much!

 

[stamp11127]

Check fuse #105 in the battery junction box with a test light or meter. The circuit is hot at all times.
If the fuse is good and powered, check voltage on pin 1 of the blower motor control connector. It should be a brown/yellow wire. Inspect ground 203 behind the lower right kick panel. This is checking the supply voltage to the bcm (blower control module).

 

[chrisblue23]

Check fuse #105 in the battery junction box with a test light or meter. The circuit is hot at all times.
If the fuse is good and powered, check voltage on pin 1 of the blower motor control connector. It should be a brown/yellow wire. Inspect ground 203 behind the lower right kick panel. This is checking the supply voltage to the bcm (blower control module).

I took the clear plastic cover off the fuse and tested it when the ac was on in accessories. It has no power to fuse 105. What would be the culprit?

 

[chrisblue23]

I checked the fuse and even put a new one there and still no power.

 

[stamp11127]

If the fuse isn't getting power then changing it out for another won't accomplish anything. It won't have power either.

See page 1 of the ac wiring diagrams. When you tested the fuse did you check the light or meter first to make sure it works? You also need a good ground for the test. If you can get the connection point on the engine or battery post you should be good.

If you are sure the fuse isn't powered then it is time to inspect the wiring in the fuse box. Usually they are connected to a bus bar down the center.

 

[chrisblue23]

I checked it out with a meter a few times and no power. So I’ll probably have to check the wiring. I recently replaced the negative power cable to the battery as it was super corroded. Would that have anything to do with it? It stopped working a few months after that.

 

[chrisblue23]

Yeah I tested the meter on the battery posts and got a 12.8v reading so it works.

 

[stamp11127]

It would if there was a bad connection in the cable. Place the red lead on the positive battery post and the black lead on chassis ground/engine. If you read battery voltage then you are probably ok, if not then you have a bad connection.

 

[chrisblue23]

I checked for ground in multiple places and I can’t get a reading on parts of the chassis and sometimes I get a weak reading in others. Even on the engine block I get a 12.01V reading instead of 12.76V like the battery shows. Probably my culprit right there. Got a lot of wire replacing to do then.

 

[chrisblue23]

Sometimes it also takes my engine 4-5 seconds to turn over. Probably not getting enough juice due to corroded cables.