Awhile ago I lost my A/C and discovered that it was the O-ring inside one of my hubs. As a short term fix I just taped off the vacuum line connection at the Pulse Vacuum Hub Solenoid. For the long term fix, I replaced the hub.

Then one day my A/C went out again and now I can't seem to pinpoint it. Read on for my troubleshooting and then tell me what you think.

I checked out the #28 and #30 fuses. They are fine.

I checked the hoses going to the hubs and they seemed intact, but when I disengaged them I got no suck from the vacuum pump. I looked at the other lines and they seemed ok, as far as I could trace them.

I tested the hub solenoid (PVHS) for resistance and got random numbers read across all the connections. At no time did I get a zero. I know my digital ohm reader is working because I touched the two terminals together and got a "zero".

I'm not too sure what a running vacuum pump sounds like anymore, I can hear mine clicking when I turn the key to the "on" position. It does sound kind of weak, but "weak" is subjective without hearing the vacuum pump on another PSD.

What else am I missing here?

 

Unplug the vacuum line off the pump and listen to make sure it's coming on. If it is, pull and block off the ports for one hose at a time until the AC starts working. Once you've isolated which line has the leak in it, trace it downstream to find it.

Vacuum pump failures are pretty rare, but if your pump won't come on with the key on and a line disconnected, then I guess it would be time to check the electrical side or the pump itself.

 

Ok, when the key is turned to the "ON" position (the engine has not been started), and the fan is turned "OFF" I do not hear anything coming from the vacuum pump. But I don't know if this is normal or not.

I hear the fan blowing when I turn the air on.

 

While these red beans are heating up I will go look one more time.

 

Yeah, after properly identifying the vacuum pump in the picture in this thread, https://www.ford-trucks.com/forums/1...questions.html, I am certain that no signs of life are coming out of the vacuum pump. It could be ****-up, but is there a way I can test it?

What else can be causing it to fail? It'd be good to know before I buy one.

 

I did some more researching and came up with some information. The part number at Autozone is 904-214.

Some other parts numbers include:

4C3Z2A451BA, 6C3Z2A451A, 6C3Z2A451BA, F81Z2A451BA

I had a vacuum leak last year and it was in the hub, as stated earlier in this thread. I am thinking the vacuum pump just wore itself out and gave up the ghost. It's probably in vacuum pump heaven smiling down on me. Anyways, whenever someone is looking up the parts for you, be sure to ask for the ELECTRIC vacuum pump, not the belt-driven one that works for the brakes.

I would buy from Ed, but I need this thing today, so I will just get it from Autozone.

I will report back, but if you have any info/pointers, I definitely want to hear them!!

Also, is there an app for FTE for smart phones?

 

Ok, I plugged the new vacuum pump in aannnnnddd....no dice.

WHAT THE HELL IS GOING ON!?!? lol This thing is starting to kick my ***. Ok, so after taking a deep breath I checked to see if I could hear the pump come on. Nope, can't hear it. I left the key in the "ON" position and walked over to the newly installed vacuum pump. No signs of life. I also checked for voltage going to the vacuum pump and got 12 volts.

What am I missing here? There's no way I got a bum vacuum pump, right?

 

The new vacuum pump from AutoZone was defective. I got another one and it worked, but that one had a nipple broken off. Getting ANOTHER one today and will report back. Thanks guys.

 

Got that new vacuump pump, installed it, my woes are over. I finally have A/C and autolocking hubs again!

TIP: If you're not sure if you are hearing your vacuum pump or not, you can feel it vibrating when it is running.

Thanks, Chris, for your help!