Help me fix my customers AC!

[drumminforev]

My customer has a 1997 ford explorer 6 cylinder. His compressor locked up, so he had someone replace it and recharge. It only cooled to 68 degrees because it cycles. I hooked up my gauges, and concluded that its the low pressure cutoff switch causing this. At an idle, it will stay at a constand 45 low 175 high.

When reved to 2k rpm, the low will continuously drop steadily til it hits 20psi, then the switch shuts it off, and it repeats.

Now, I am assuming its either the orifice tube that got clogged when the compressor locked up or the accumulate is clogged.

What do you think?

Also, I CAN NOT figure out how to remove the accumulator, and I can not locate the orifice tube or figure out how to take apart the evap box.

Here are the pics of the piece of the accumulator and the fitting I cant understand. Someone, let me know how this is supposed to come on and off and if a special tool is needed.

RECAP
Help me disconnect the accumulate.
Tell me where the orifice tube is located and how to remove. I have the tool.
Help me diagnose this problem, whether or not I am correct.

 

[fobrnno]

you are going to need a spring lock tool to remove the line where the red arrow is pointing to.

and the orifice tube is in the other line of the accumulator where the nut fitting is. you might need a needle nose pliers to remove the orifice tube from the line.
there is no need to take the evap. box apart.but while you have the accumulator off and to replace it you are better off too flush the whole system out with some sort of a/c flush to remove any debris left from the failed compressor.and install your new parts in a clean system .

 

[drumminforev]

Hi. Thanks for letting me know about that tool. I'll try autozone for that.

The orifice tube is in that big nut that we see in the first pic?

 

[fobrnno]

ding ding ding you win the prize.

the orifice tube is in that fitting, some time they come out easy and some time its a *****, but you will get it out

 

[shamaal]

I've attached a picture where the orifice is. Your blue arrow is the output of the evaporator, the red arrow is the output of the accumulator to the suction of the compressor.

The orifice is on the input to the bottom of the evaporator coming from the condensor. Two nuts, hold the left steady to avoid bending the tubing and making it difficult to remove/replace the orifice, There is one o'ring.

These Ford are orifice systems, not expansion valve systems. Do not pour liquid refrigerant into the accumulator like you can a receiver.

 

[drumminforev]

I can not figure out where that is. Is it under the accum? to the side? I have seen that pic before and it did not help. My hands were way to big to fit through any of the lines. Got any ideas for reaching it? Thanks for the help.

 

[shamaal]

I would think with a clogged orifice the high side pressure would be higher, but it could be loose crud breaking up the flow. The plastic tools as shown above work, I use a scissors type gizmo from an autostore.
Make sure system is empty before disconnecting things. WEAR EYE PROTECTION!
If replacing accumulator add 3 oz of PAG100 oil.
After inspection and repair, evacuate for 1 hour before charging.

Read stickies above.

 

[AMMO_HOOAH]

Do you see that Round bracket on the left of that last pic? That's the accumulator bracket. That pic is strait down into the engine bay.

 

[drumminforev]

Back to my original question...do you think it really is the acc or tube that is causing the low pressure on the low pressure side. And do you think I should flush any parts...if so which and what are some tips you recommend for doing it without a flush gun.

 

[drumminforev]

Well, the high pressure goes up proportionally as the low pressure goes down, until the switch turns it off, then repeat.

 

[drumminforev]

Do you see that Round bracket on the left of that last pic? That's the accumulator bracket. That pic is strait down into the engine bay.

Ohh that helps. I thought it was a side shot for some reason. I don't exactly remember seeing that hex with a buldge, but I will double check.

 

[shamaal]

Go to condensor and follow the line back on the passenger side, the orifice is between the condensor and the evaporator, under the accumulator. The pic is from a OHV vehicle. Pull up the fluid containers an yours and it should be under them. You can also remove the wheel well cover and gain access.

The pressure switch opens at < 24.5 and is closed at>43.5. Under normal operation it will close, draw down the pressure, turn off and repeat cycle. The pressure differential across the orifice is what mechanically turns the liquid to vapor. Cycle rate will be determined by ambienttemperature and how much heat is removed by the compressor.

The evaporator assembly is held on by 3 nuts and comes out as an assembly. 11 screws hold the box together. While evaporators go bad, they fail relatively rarely.

If it was me and I hadn't done anything prior to the vehicle:
1. Evacuate the system, hold vacuum for 15 minutes to check for leaks, vacuum for >45 min more.
2. Fill with amount on EPA sticker next to hood latch. Ensure cooling (delta of 40 deg)
3. Troubleshoot if necessary, if goes bad later put in leak dye and troubleshoot. For a garage with A/C equipment a sniffer may work better and use of an electronic sight gage to aid in troubleshooting.

 

[drumminforev]

Thanks for the help. It is not a normal operation thing however. If the RPM is 2k or more, the pressure will rapildy drop down to 20psi low in about 5 seconds, then turn off. wait about 5 seconds, then turn back on for 3 more, then off. I am thinking there is a clog. Im going to see what i can figure out

 

[Glacier991]

Your symptom description fits a system low on refrigerant (not necessarily but that is my call on it) with a partially plugged orifice tube rather well. I'd pull the tube and replace it... then evac and recharge the system. I think that will do it for you. And shmaal is correct on the location of the tube... it is underneath on the lower evap line... kinda a pain to get to in some cases.

ps. For those reading this forum, the advice from shmaal is top notch professional quality advice, heed it.

 

[drumminforev]

well i pulled the orifice tube and it was 100% clogged with metal gunk and other ****. So i flushed the ac lines a few times, replaced orifice and recharged. At a stand still, reving to 2krpm it would cool to 55 degrees. Now, i get a call back from him saying it stopped blowing cold at all, so i have to go back and see whats goin on.

Why did it only cool to 55? it was about 85 outside

 

[Glacier991]

What were your gauge readings when you had vent temps of 55? The trouble with a system that has suffered the black death is the danger that you do not get everything out on a flush, and the tube plugs up again, causing a come back. That is why many shops just quote for a complete system rebuild. IF you still have refrigerant in the system (eg it is not a leak causing this issue) I'm betting the orifice tube is once again plugged... but you didn;t say what he described as total symptoms was... might just be a leak somewhere. Let us know....

 

[gijoecam]

Those numbers sound a bit low.... I'm no AC pro by any stretch, but my pressures (with the compressor running on MAX AC, both blowers running on high, 100 degrees ambient) my low pressure was stable at around 30 PSI, high side was 250@1500RPMs. It's cooling down into the high 30s on max/high.

I will print out the AC service procedure in the AM. It requires a particular weight of charge, and then from there, you need to verify high and low pressures against ambient temp, as well as the duty cycle of the compressor once the interior temperature stabilizes.

-Joe