Hey everyone,

So I'm new to the forum and of course nobody likes a dumbarse who was too lazy to use the "search" function... so after spending countless hours these last few weeks on this forum as well as other sites through a search engine the only threads I was able to find that describe similar symptoms were incomplete and OPs didn't care enough to post resolution to their issues.

Anyway... here is a tricky one. Bought a '01 F250 5.4L Auto with 150k. It's a work truck and been neglected pretty good. Working on the A/C problem, here is what I got...

Symptoms
Starting the truck with A/C on will yield about 15-30 secs of ice cold air (compressor engaging) then compressor quits and here comes the heat wave. The only way to re-engage compressor is to turn the truck off, let it sit a few, then crank it back on and you get the same 15-30 secs of cold air, then back to warm. This can be reproduced pretty consistently.

Jumping A/C clutch relay allows compressor to engage and blow ice cold air in the cabin, as it should.

Background:
I've done some troubleshooting on this so far, of course. At first, tried "tapping" the compressor and jumpered low pressure switch. Nothing. So thinking it was my compressor I had sys evac done, compressor replaced, installed new accumulator, new orifice tube, refill, check pressures... nothing. I get 12v at the low pressure switch harness. No open/blown fuses in the cabin or at PDB. So I know, mechanically, my A/C system is good.

Discovery
As I said, we're able to get the compressor to engage by jumpering the A/C clutch relay in the PDB. And that's as far as I got. I pulled the A/C clutch relay and wondering whether I have the right one in?? It is identical to the Blower Relay right next to it. But I read on justanswer.com (I have an F250 that has power to the low pressur... - JustAnswer) someone described that the relay should have GROUND at pin 85 and POWER at pin 86. Using my voltmeter I have the opposite, POWER at pin 85 and GROUND at pin 86.

I may be totally loosing my mind but can someone shed some light on whether I have the right relay in place and what should I be reading at each pin? And ultimately, what could be the culprit in my situation here?

Many thanks guys!

 

What is the presures when the truck is turned off and what is the presures right before the compressor kicks off? It is still posable there is a clog somewhere. There is a way to jump out the low and high presure switches. You should try that and see if it stays on. If it is a clog and the high presure switch is cutting it off dont let it run too long because it could blow out o-rings hoses or any number of things.

 

Don't believe that it is clogged. I had my mech did a flush and evac on the entire system before refilling it with freon. Besides, I can get the compressor to engage and it will work no problems as it should via A/C clutch relay.

If my memory serves me right, I believe the low pressure was right at 45psi before compressor kicks out and then climbed to 120psi and stayed that... I could be off on those numbers though.

I didn't mention this before but I do have a check engine light on due to a bad coil on #5 cylinder, PO355. The wiring to that coil doesn't look right and looks like it has been messed with (spliced after being burnt maybe?). I'm not sure if it is related or not but it almost feels like the PCM is shutting the compressor down through a relay... maybe a safety mechanism?

Just got a Haynes manual at a local Autozone... gonna dig in...

 

Haynes is worthless, 2001 F-250 350 450 550 Excursion And Super Duty Wiring Diagrams - Helm Incorporated

Every wire, connection, color, etc etc etc. Its the same books that the factory wrote initaly before they tooled there assembly lines to build the trucks.
Ive used them and there WELL worth the money. And it covers any electrical problems on that year. Could help alot of fellow members if you do get it.

 

Problem fixed.

Ok... remember how I said earlier I had a check engine light on? Well, apparently replacing the coil pack on #5 cylinder with a one that works and clearing the code did the trick! The A/C is now blowing nice and cold! Turned out to be a good weekend after all!

Lessons Learned
Sometimes, your check engine light can cause your A/C compressor to not engage, even if you see voltage at low pressure switch, have a good PCM, good A/C clutch relay, just replaced the compressor, accumulator and orifice tube before flush and refill on freon. Have a check engine light on? Start with that before anything else...

 

Before closing the thread out...

I did notice that the air although blowing cold was not as strong as it blows on my e150, e250 fleet vans. I remember coming across some threads that speak of blockage by crap like potato chips bag... etc... So I went looking... Did find some debris (and a $1.00 bill) cleared that off, pulled the blower... vacuumed all that stuff, cleaned, etc... Still not as strong.

Then I looked at the evaporator (right next to the blower) when I took the blower out again to see where it's getting its airflow... and lo' and behold... it was plugged up! I mean grimmy, caked in dirt and sand was in there like I've never seen before! So I'll tackle that next... anyone know the best way to clean that up?

Taking the enclosure apart shouldn't be a problem... but trying to hose that off looks like I'll have to cover the motor pretty good and some other stuff??? Anyone done this?

 

The best way to clean it would be to remove it and use AC coil cleaner. (which is toxic and you need a friend with a license to buy it)

Makes you want to find a cabin filter kit doesnt it?

 

Alright... so the cleaning was actually pretty simple. Took out the blower (3 screws) and simply used a garden hose to spray it from inside the blower enclosure, right through the evaporator. It took a little while to break down and hose off all the debris but it all drained through the opening on the other side of the evaporator.

Reassembled and tested the air.... and it blew stronger than ever!!! Woohoo! Sweet, I can now take on CFL heat without breaking a sweat.... Except when I'm outside at high noon of course! In any case, issues resolved and I can now close out this thread.

Anyone else doing this, be sure to spray Lysol or some disinfectant after the evaporator dries off to ensure no fungus or mildew gets form on the evaporator coils.

Radzer... thanks for chiming in and participating in the thread. Appreciate your input.

 

Did you use any kind of cleaners or chemicals? Because it sounds like you might have just removed debris. Not actualy cleaning the coils. The dirt thats stuck to the coils if cleaned off properly you would get alot better heat transfer into the coils and out the truck.

Check this video for a good example

YouTube - HVAC (Coil Cleaning)

 

Lol... it's always easy to clean condenser coils when they're right in front of you like that! The evaporator coils are enclosed in this box that according to WSM you would need to remove accumulator to get completely opened and accessible. I wasn't prepared to get into that deep.

Having a 6x4" opening to work with that bottlenecked into a 3x3" opening before getting to the evaporator coil I didn't have much room. Using a mirror, I was able to see what I needed to clean... got it nicely saturated with water for about 5 minutes then carefully blasted it with a hose making sure I didn't bend coil fins. Then used a mirror to re-inspect and you could actually see the dirt came off quite easy and you could see nice and bright coils. There was no grease in there so I don't see it requiring too much effort to get cleaned.

Then I soaked it Purple Power industrial strength cleaner and hosed it off again. It got them coils even brighter. Used the mirror to make sure all fins were good, used a rag to get excess water out of the enclosure pooled on the bottom, reassembled and turned her up. It was BLOWING out of those vents!

I'm still going to get some Lysol or some other disinfectant to spray in there but quite honestly.... I saw no mold or calcification. It was just sand silica, dirt and bunch of other debris...

 

I just started to change out #5 plug and broke it off, having to drill out the pin that was stuck in the bottom of the plug I unplugged the coil pack and left it umpluged, i wonder if that's why my Ac quit working. Cant wait to see if that's all it is.

 

My '87 F250 total rewire project has two wires coming from the clutch cycling pressure switch (located on the accumulator). Spliced into one of the wires, down line, is another wire that I believe goes to the EEC component (I don't have the EEC component on my truck). As the wires near the compressor, there is a diode in-line on one of them. My compressor is a new Sanden with three wires going into it. One is attached to the compressor housing and is black. The other two dissappear into the compressor and both of them are black with a white stripe. All three exit the compressor and converge into a 4 inch stiff component with one wire emerging. I am confused as to how to wire this, so I went to the local salvage yard and examined the wiring on another '87 F250. This truck did not have a diode in-line and had four wires leading to the compressor????? My obvious question is "how do I wire this thing"? First of all, what is the stiff component on my new compressor with three wires going in and only one coming out? Secondly, of the three wires going into the compressor, which is the positive one (I need to attach a wire from my electric fans to this lead)? Thirdly, since there didn't seem to be a high pressure switch on either of the two systems (mine and the one from the salvage yard), do I need one? And lastly how do I wire the two from my pressure switch to the one from the compressor?