Another A/C problem

[aughtsix]

Hi Guys......

Spent the last few hours trying to find a solution on this forum. Found a lot, but not exactly.....not yet anyway.....

!998 Explorer Sport, OHC V6. Puts out really cold air for a while. Then just goes to warm air. If I manually go to fan and wait 2-3 minutes....COLD air again!!! In traffic or road speed.... Evaporator freezing??? I know compressor does stop. I have duplicated in garage.

A/C system has been leak checked, evacuated, and recharged twice. Once by me and once by shop. Pressures are good. Orifice valve was replaced by shop. Wasn't clogged completely, but needed a new one. Accumulator was replaced in '05. Would an accumulator cause this?

I am guessing the A/C Cycling switch by the Accumulator or the A/C cut off switch on the Compressor???

I am on fixed income and it is getting expensive!!

Any and all advice is much appreciated!!
Thanks to all, this forum is great!!

 

[safn1949]

It's freezing up,I would guess it's not cycling as it should.Open the hood and turn the AC on max and you should be able to see it freeze,a blockage will cause that also as in a drier full of gunk.But I would guess it's a high pressure cycling switch.

If and when it freezes take a photo,it can show the problem,for instance the frozen part is next to the orifice tube outlet indicating a blockage.

 

[ErnieX]

You may want to check the gap on the clutch plate. Had a similar problem and when the comp. clutch heated up it would not pull the clutch plate in once it cycled off. Can test by duplicating the condition and tapping the clutch with a hammer handle. If it sucks the plate in and the compressor runs you may have to regap the plate by removing a spacer in the clutch hub.

Hope this helps

EE

 

[aughtsix]

UPDATE on A/C Problem

Thanks for the prompt replies....

Should have mentioned all the earlier was on MAX cool. Around Rome, GA.

Got up early and got a Pressure Switch and installed. Drove 20 mile round trip to town and back. Low 80's outside temp. Worked great on MAX cool.
Hour or so later decided to give a good road test. 88 degrees outside temp. MAX cool. Went thru Mickey D's. Cold air stopped. Went to just fan for 3-4 minutes. Went back to MAX cool. COLD air, few minutes later....ZIP....No cool. Went back to fan only for a few minutes. Turned selector to A/C, NOT MAX cool. Drove 120+ miles in A/C, worked great.
Of course, not as cool as MAX, but very acceptable! Some of this was at 65 MPH on highway, some in town at 92 degree outside, stop and go traffic in Oxford, AL. I did try MAX cool a couple of times, no likee........
Seems to be a fine line in temp of incoming air over evaporator......
Next step.....Replace Accumulator???
I forgot to mention that I had put in some 134a with a stop leak in it last year. Hopefully that was all evacuated by me and the shop pumping down. Maybe that plugged up my Accumulator and/or desiccant bag????

Thanks safn1949 and erniex. I did try the tap on clutch. Didn't work. But I will remember.

Forgive the long post, I am getting to old to work on this stuff. I can still learn..LOL!

 

[safn1949]

Max recirculates most of the inside air while A/C mixes it with warmer outside air so the evaporator is probably freezing up.I will have to look it up but most vehicles used to have a temperature probe in the evaporator to cycle the clutch to prevent freezing.

I have the 2000 FSM,I will take a look and get back to you.

Ok,I will type what it says in the FSM. The A/C cycling switch interrupts compressor operation before the external temperature of the A/Cevaporator gets low enough for the condensed water vapor to turn to ice.
It does this by monitoring low side line pressure.Low side of about 30 psi= 32 F.The switch tries to maintain that pressure by cycling the compressor.

I would replace the cycling switch,it will be right after the dryer.It has a shrader valve so you just unscrew it and replace it.

 

[aughtsix]

safn1949.........

That is what I did.............Installed a new A/C cycling switch.....

I understand the difference between MAX and A/C.....

I appreciate your response..........

 

[aughtsix]

Next Step

Since changing a/c cycling switch, as suggested by safn1949, much appreciated, helped greatly.
I am still freezing up on MAX cool, even with thermostat turned to lower temp. I need MAX cool as it allows my wife to breathe better in vehicle as it doesn't allow as much pollen in outside air to reach cabin. My wife suffers badly from allergies.
Does anyone think changing out the accumulator would help my problem??

 

[aughtsix]

Pressure readings

A/C cycling switch/low pressure switch and orifice tube replaced.
90 degrees ambient temperature. Wall thermometer.
95 psi static pressure on both gauges.
Turn on A/C....45 psi on low side, 250psi on high side. About 1400 rpm.
Max cool, fan on high, windows down.
Center vent drops to 45.3 degrees.Digital thermometer.
Water running from evaporator.
Runs like this for 10 minutes or so. Constant pressure reading 45/250. Compressor running all the time.
Then compressor disengages. Goes back to static pressures. I wait a few minutes. Will not reengage until I turn off A/C for a few minutes.
Accumulator??????????
Thanks any help!!!!!!!!

 

[team]

I wonder if it could be your fan clutch going bad. This would result in low airflow across the condenser allowing the pressures to get to high. Then the high side switch cuts off the system until pressures drop to safe levels?
If you could reproduce the problem in the driveway and then jumper the low side switch and then the high side switch to see which one turned the system back on it would help narrow the problem down.

 

[aughtsix]

I checked out my fan by sticking a rolled up newspaper into it. Didn't even slow the fan down that I could tell.
I tried jumping each switch separately after compressor had shut down. Neither one would make compressor engage.
I did disconnect each switch separately while compressor was engaged. Compressor disengaged with either switch disconnected. Does that seem correct??
Also, is there a shrader valve under the High Pressure switch like under the Low Pressure switch??
Many thanks for your input!!

 

[team]

when this happens have you pulled the plug to the compressor coil and see if it is still getting power. If it is then your problem is the coil/clutch.

 

[aughtsix]

No Power

Nope....

No power to clutch assembly when clutch not engaged...........
Could I have too much refrigerant in system to cause high pressures or could accumulator cause same?????
Using Harbor Freight gauges....
Thanks.......

 

[budwich]

do your self a favor and get a meter and start checking for voltage along the "switch route"... at the high switch, at the low switch at the cutoff relay.... you will find your answer.

 

[team]

Use a multimeter to check the continuity to find out which switch has been kicked open (low side or high side) when the system stops working. Then the problem will be narrowed down to the low or high side and we can go from there.

Alldata says the low sides kicks open at 22-28psi and the high side kicks open around 420psi.

So check the continuity and let us know what you find.

 

[aughtsix]

It like to froze me to death on Friday. 80 degrees and rain.
Saturday in traffic and 90 degrees, it stopped. Pulled into parking lot and popped hood, grabbed meter, pulled high side connector, had continuity. Plugged switch back in and compressor engaged before I could check low side???? Then had cold air off and on as long as I went to fan for a few minutes then back to a/c. In traffic and at road speeds. Never a place to pull over again when a/c stopped.
Since I already replaced cycling switch on accumulator. I bought a new high side switch on way home. What the hell!! Got home and pulled connector and red center part of connector came apart. Replaced switch and plugged back in. Still making contact.
Today, Sunday, drove 45 miles to metro Atlanta. Cold air all the way. In traffic, idling in parking lot, whatever. 90 degrees. Left parking lot, lost a/c. Forgot my meter!!! Drove for 5 minutes without going to fan. Still no a/c. Go to fan for less than a minute, timed, back to a/c. Cold air starts up. Go thru same thing several times on way home. Go to fan for 45 seconds or so, switch to a/c and cold air for awhile. I have tried several times to try to replicate in drive way, doggone compressor won't disengage for anything. Even covered up grille with cardboard. Just keeps cranking out COLD air???????? I did order a new connector, about 5 days to get it.......
I will keep trying for continuity checks??
Thanks for all the info and advice!!

 

[team]

i had something similar happen on a dump truck i worked on. the low side switch male prongs were loose inside the female plug in. Compressor would sometimes work and then not work. Finally bent the prongs in the switch so they were touching with good friction when I plugged the female wiring harness back to it. So far it seems to be working.

 

[aughtsix]

Team......

Thanks so much!! After I found the faulty plug it has crossed my mind, some sort of vibration or intermittent interruption. I shall find out, when I get the new one connector!!
I appreciate all the help from everyone!

 

[aughtsix]

S o s

Same Old S***!!

Replaced wiring connector to high side.
Went for a test run.......Same thing???????
Guess I'll take to shop.......
Really appreciate all the help!!!!

 

[ranger7ltr]

One item you mentioned a ways back...

That the evaporator drain was dripping...Have you checked to see if the evaporator drain continues after the a/c stops cooling?

It is a long shot but if the condensation is not running out fast enough it could build up inside the case and freeze in the lower part of the evaporator...

 

[Gus Gorilla]

Another item you mentioned a ways back was that LO side was 45 but discharge temp was 43. Somewhere in there you might have a measurement tool inaccuracy. I'm leaning towards the gauges. If the LO side is 45psi as a rule of thumb in warm climates such as yours you could expect 10 degrees above that from vents. Meaning 55F. It is unheard of and as far as I know physically impossible to have a lower temp discharge than the LO pressure PSI.
If the vent was at 43.5 then the evaporator would be roughly 33.5 as an estimate. Roughly means it might have been lower, such as freezing.
I'm pretty confident you are dealing with a freezing event since switching to vent fan corrects it for a while. I'm also fairly comfortable in thinking that the gauge set could be wrong.

Just my .02 and some food for thought.