A/C Compressor Problem

[JohnnyRook]

Hi All,

My A/C has not been working. When I push the button the light goes on and it blows air, but it doesn’t get cold. Today I had the truck running and the hood open. I pushed the A/C button to see if the compressor came on. It seemed to come on but after a few seconds it turned off. Then it turned on a few seconds later and turned off again. I assume it would have kept doing this indefinitely but I turned it off.

Any ideas on what the problem is? Do you think I’m low on Freon and the low pressure switch is disengaging the clutch?

Much appreciated.

 

[AMMO_HOOAH]

That's a pretty easy check with a $8 dollar gauge from autozone. There are a lot of AC savvy people on here, so I'm sure someone will chime in. In the mean time I'd start with a pressure check.

 

[doonze]

Well, on mine it does work, but engages and disengages every few moments anyway. I don't know for sure, but it seems like about every 30 seconds or so, I can watch it and see it engage and disengage, hear it too. My Hyundai does it about the same. How often is it?

I'm not real sure it will even engage the compressor if it detects no pressure on the coolant side, but I'm not sure. A/C is kinda voodoo to me, pretty much it's just the magical cool stuff that keeps me from sweating on hot summer days. (or causes my truck to overheat as the current case seems to be)

 

[rizzjc]

It should not engage every few seconds. I think it should cycle a minimum of 10 seconds. If it doesn't get cool at all, then it sounds like it's completely empty. Might be easier to take it to a shop, and see how big a leak they find. Did it happen suddenly, or over time?

 

[Explodr94]

You could have a bad orfice tube. Your a/c would not blow cool if that part was bad. You should also have you system pressure tested, as stated before to check for leaks and freon level.

 

[fixxxer]

If the pressure get's below a certain threshold, the pressure cutoff switch kills power to the A/C compressor clutch. If you have a slow leak, and it will happen sooner or later due to seals drying up, cracking and shrinking, your A/C will do exactly what you described. The a/c clutch will engage for about 4-5 seconds then disengage for about 5-8 seconds then re-engage for another 4-5 seconds and so on.

 

[JohnnyRook]

Okay so I bought a recharge kit with a pressure gauge. I turned on the truck and the a/c and checked the pressure. For the few seconds that the compressor engaged the pressure was well below normal. When the compressor disengaged the pressure increased but still stayed below normal. Is this normal to see the pressure fluctuate like this? Am I safe in assuming that the pressure in my system is low in general?

 

[fixxxer]

There seems to be a lot of questions lately about the 1st Gen Explorer's A/C not working properly, I thought I'd throw some diagnostic aids up to the forum so that they may help others in troubleshooting A/C issues with the 1st Gen models.;

 

[fixxxer]

And a slightly newer A/C refrigerant system pressure diagnostic chart:

 

[rizzjc]

Okay so I bought a recharge kit with a pressure gauge. I turned on the truck and the a/c and checked the pressure. For the few seconds that the compressor engaged the pressure was well below normal. When the compressor disengaged the pressure increased but still stayed below normal. Is this normal to see the pressure fluctuate like this? Am I safe in assuming that the pressure in my system is low in general?

Which side did you check (high or low) and what was the reading? It should be somewhere between 25 and 45 on the low side.

 

[JohnnyRook]

I checked the low side, but the reading was fluctuating. When the compressor engaged (for 2-3 seconds) the pressure dropped. When the compressor disengaged (and stayed off for 2-3 seconds before it re-engaged again) the pressure would rise. The compressor engaging and disengaging would continue along with the fluctuation in the gauge reading.

I talked to the guy at the auto parts store and he thought it was a sure sign of a leak. When the compressor engaged and Freon was flowing it leaked and the pressure drops. It drops to a point where the low pressure switch shuts off the compressor which allows the pressure to rise again and the compressor engages again. Does this sounds like it's true?

If I have a leak how good are the leak detection kits you can buy at the auto parts shop?

 

[rizzjc]

When the compressor stops, the high and low side will equalize. When the compressor starts, the low side will drop, and the high side rises. I suppose if it is really low, you might see if fluctuate significantly. I don't think it would be showing a leak as it cycles on. I just think it's equalizing the pressure. The question is, how low was it? What did the low side fluctuate from and to? How low? How high?

I'm no expert, but I've been spending the last couple weeks investigating my system. It's all new to me, but it's fresh in my mind.

If it nearly empty, then you could just take it to a shop to put in a leak detector (dye) and refill, and see if it leaks out immediately. If not, you might be OK for a while. I've heard it's only about $70 to have this done. If it leaks you can bring it back and they'll look for the leak (i.e. the dye).

 

[JohnnyRook]

So when the compressor switches on it drops to 17 psi (in the low zone). Then the compressor switches off and it rises to 43 psi (in the normal zone). As soon as it hits 43 psi the compressor switches on, the pressure drops to 17 psi, and the compressor turns off. It takes about 2-3 seconds for it to raise/lower which means the compressor is on for 2-3 seconds then off for 2-3 seconds.

 

[ma96782]

For a '94 Ford Explorer..........

the Haynes book says ('94 Ford Explorer w/factory R-134a system)........at ambient air temp of 80 degrees F, hi velocity fan in front of the condenser. Engine running at 1500 RPM.........you should have 22-50 low side and 160-250 high side pressure. Capacities: oil 7 oz and R-134a 2.25 lbs (36 oz).

For proper AC work...........

You'll need a two gauge manifold set to hook up to your system. Something like this one will do for the home DIY guy........

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?itemnumber=92649&Submit=Go

*Harbor Freight will honor the internet price if you bring a copy of the internet ad to the store as proof.

Or just take it into the shop.

It may just need a can of R-134a to get back to working order or it might be a leaking part, bad compressor or bad switch.

The tech can test for a leak. He'll either use a dye or a sniffer. Or if it's something else, he'll tell you.

If the tech says it is leaking.

Ask, where exactly is it leaking from?

Then you'll have to decide if you'll change the part(s) yourself or let the tech take care of it.

If you plan on doing the replacement of part(s) by yourself, have the tech recover the gas from the system before you take it home.

Once at home, replace the bad part(s).

Note: If your accumulator has been exposed to air.......it'll need to be replaced. As soon as possible after the replacement of the accumulator (IMHO: that day), you should re-charge the system.

Then, once the bad part(s) are changed......next is the vacuum and test.....before the system is re-charged.

IF you don't have a vacuum pump........it's back to the shop. And since you're letting them vacuum and test it......you might as well let them re-charge the system (assuming there were no leaks).

IF you have a vacuum pump and two gauge manifold set........then, vacuum and test the system. IF it's GTG then proceed with the re-charge.

Perhaps it's too much money to spend on tools and/or too much effort to learn (I've only covered the basics)........you decide how you want to proceed.

Aloha, Mark

PS........my underhood sticker said that my system used 1 lb 8 oz of R-134a.......well, that was WRONG. It needed 36 oz of R-134a. The FORD guy who *&%^ that up should have been shot.

 

[rizzjc]

I'm surprised it runs at all. 43 psi when OFF is really low, and the high and low will equalize.

 

[JohnnyRook]

When the system is properly pressurized, the low side pressure should not fluctuate like mine currently does correct? At a temperature of 80 degrees the pressure should be a consistent 40-50psi right?

 

[rizzjc]

Yes, when the compressor cycles, you should not see the pressure change on the high or low side. It should hold.

I charged mine- it was a little low, but not bad. Now it's within spec, but still cycles more than it should. Ice cold, as usual, so I'm leaving it alone until it explodes or something.

 

[Maniak]

I'm pretty sure that the a/c pressure should NOT hold when the compressor dis-engages.

As your charging the system, and while the system is a little low, the a/c will cycle becuase the lower pressure gets too low (<20 or so). Once it does (de-energized the a/c clutch) the low pressure side immediatly starts to come up. Once it comes back up to around 35psi the compressor kicks on again..

All I'm saying is that when the a/c compressor isn't running (clutch not engaged) the pressure will equalize. That means high pressure will bleed to the lower pressure side.. If it cycling it is becuase the lower pressure side is getting too low.

When the a/c isn't running the high and low side pressures will be about the temp of the condensor. That means on a 100F day, you'll have "about" 100 psi on both sides.

~Mark

 

[JohnnyRook]

So the fact that my low side pressure is only 43psi when the compressor is off means my system is very low (temperature out here is in the 80s) correct? I'm going to charge my system, but I'm paranoid about over pressurizing. I should charge it until the low side pressure is 40-50psi while the compressor is running. Is that right? At that point the compressor should stay engaged and the pressure will stop fluctuating?

Sorry to keep asking so many questions, but it’s hot out here, and I’m too poor to get this thing fixed in a shop.

 

[Maniak]

Assuming your using a manifold gauge to keep an eye on the high pressure...

"I" would put in r-134 until it stays about 30-35 psi when running on the low side.

While putting it in, keep an eye on the high side. it should be 250% higher than the ambient temp at the condensor.. In general.. on a 100F day look for 250psi or so..

Then bring up the rpms to say 2000 and hold them.. if the low side drops enough to make it cycle then add a little more BUT watch the high side.. if you get too much in the high pressure will go up.. IIRC the blow off safety valve on the back of the compressor is set to "around" 350psi.. Remember, when it gets hotter out you will get higher pressures on the high side.. so 250psi when its 80F out means it will be over 300 when its 100F out.

~Mark