Ok,I posted this in the diesel forum and my post got hijacked. I'm gonna try here. A couple of weeks ago, my AC started acting strange. When I put in MAX AC, there is no change whatsoever. The fan feels like it's barely blowing. I have checked the actuator and it appears to be working, but really slow to close. With it in MAX, it feels and sounds as though it's kicking in and out. I have been watching the actuator while it does this and there is no movement on the actuator.
Then, the other day, the AC was working, still had the same problem, but it was at least still blowing. Turned the truck off for a few minutes. When I started it back up, nothing. No fan at all. Tried turning off and on, with the truck and controls. No change. With the truck running, popped the hood to see if I could see anything, and I could not find anything. Frustrated, I slammed the hood. BAM, the fan started working. Still had the original problem, but at least the fan was blowing again.
Nothing changed for a coue of days. Then today, stopped for fuel, started the truck, no fan. Popped the hood and slammed it. Fan started working. I have not been able to locate any cracked vacuum lines, but then again I have been focusing on the actuator.
Can some one please give me some guidance on things to check. These 105 degree days are a pain with an AC barely working.

 

Ok, first off what year and model do you have. Might help a bit.

Sounds like you almost troubleshot the thing down to an electrical gremlin. I'd be checking the connections and wires for a loose or poor connection. Also your blower motor may be going out, if it only works on one setting and even then its only sometimes.

So when the fan is blowing is the air cold? If so, its likely just a HVAC problem and not AC. Some people may be seeing AC Problems and skip over when they may some have knowledge on the issue.

 

If you have the A/C turned off, do you have the same issue with just the fan intermittenly not working? Does it blow hot air just like it should?

In other words, i think you need to explain better if it is the fan, or the A/C that has the issue.

When fan motors are on thier way out they are like starters, sometimes they will start up after you give them some motivation by a tap with a hammer or a fist to the dashboard.

 

Sorry about the lack of information. All of my truck info used to be n my signature, guess it doesnt show up when sent from my phone.
I have a 1997 OBS CC PSD.
Here is an update as of this morning. Went out to start my truck this morning, no fan. There is no fan with or without the AC on. I tried the same trick (slamming the hood) that has been working. This time that didn't work.
When it was working, I had all the fan speeds, somewhat. You could feel a difference between all of the fan speeds, but, none of them were blowing as hard as they should be. For example, with fan speed turned to low, you could just barely feel any air movement if you placed your hand on the vent. It didn't matter if you had it on vent, AC, Defrost, or Floor. And yes, with it on vent, you could obviously tell that the A/C was off because it soon started blowing hot air.

 

Sounds like the blower motor went out, its been limping along for awhile.

 

That's kinda what I figured this morning. Now I just have to figure out where to get another one.

 

I checked broncograveyard and they don't list one with air for your model. Might try local parts stores.

 

Update. Just pulled the blower motor. Just for curiosity, I plugged it back in and it worked. Guess, I'm back to square one, except now I know it's not the blower motor.

Can some one tell me if this could possibly be a vacuum problem?

I'm kinda lost on where to go in the trouble shooting process

 

Not necessarily... You could have one or two failed windings out of the many that your blower motor has. Every once in a while when you are lucky it stops on the bad winding and does not start moving until gets a little jolt to rotate by slamming the hood or something.

 

AC Vacuum Selector Valve Assembly

Could be this. Vacuum could be the culprit, I figured when you didnt have any vent airflow you would have heard the blower working or not.

 

I'm gonna try to explain what is going on, not sure if I can though. So bare with me

A couple of weeks ago, I noticed a difference in air flow when using Max AC. It still flowed air, but not as much as in the past. I tried moving the selector ***** (fan speed, and function). Nothing improved the fan while in the Max setting. Even when the function was set to regular AC, I noticed a decrease in performance. I checked the actuator and it was working appropriately.
While this problem is going on, I can hear fluctuations in the fan. Almost like it's speeding up for just a second and then returning back to where it was prior. There is no regularity to it.
Then, the other day, this same problem was still going on. Only this time, after turning my truck off for a while, then after starting the truck, I noticed that I had NO fan at all. I tried turning off the truck and restarting it several times. No luck. I tried turning off the A/C several times, no luck. I got out of the truck and opened the hood to see if I could see anything wrong while it was running. Of course I couldn't. Frustrated, I slammed the hood and the fan started working again. Not sure if it went back to the original problems or started working correctly. This happened again yesterday, same thing, slammed the hood and it started working again. This morning, it happened again. Only it didn't start working after slamming the hood. When I removed the blower motor, I plugged it back in just to see what was up. The fan worked.

After explaining it, I'm kinda leaning towards the fact that it's a fan issue. Not exactly sure if it could be a vacuum problem or not, turning the fan speed control know, I have 4 different speeds, although not what I feel they should be.

If anyone has any input, please feel free to speak up.

Also, when I looked at the coil with the blower motor out, I noticed it was pretty dirty. What is the best and easiest way to clean it?

Hopefully that clarified what is going on.

 

Compressed air would do a good job... blow out the fan motor good too. Try taking the blower motor out and either plug it in out of the truck or hook some jumpers to it from your battery. when you give it 12V+ and ground, it should spin at full flow. Give it power, and take it off until it stops spinning. try to see if at one point of rotation, it will not start moving, but if you give it a little spin with your hand it will then start up. Either that or go to your scrapyard, get a new motor and try it for a week and see if the problem comes back.

 

It sounds like the "speed reducer/resistor" or it's plug.. It should be on the airbox outside about 5-6 inches towards the drivers side, just behind the receiver/dryer..

Check the plug real close, look for burned contacts...

No Vacuum will not cause no fan at all, it may not blow out but you will hear it run...

 

Update....
Replaced the blower motor and the vacuum selector switch. Everything works like a champ. I figured the vacuum switch was bad or going bad because I could hear a vacuum leak under the dash.
Thanks for all the guidance through this process.