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Old 08-11-2004, 07:29 PM   #61
JaneiR36
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Low side pressure = 85 psi. I've read something like 25 is where it should be at....... would the AC shut off because of too high pressure? hmm....... Also, I can't seem to locate the high side, so I don't have any readings for that.

So that revving sound was just the engine cooling fans, and not the compressor. I was looking at the compressor as the AC was running. All the belts and everything seem to be moving (with no change whether or not the AC button is pressed). Oh well.
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Old 08-12-2004, 12:58 AM   #62
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Quote:
Originally Posted by JaneiR36
Low side pressure = 85 psi. I've read something like 25 is where it should be at....... would the AC shut off because of too high pressure? hmm....... Also, I can't seem to locate the high side, so I don't have any readings for that.

So that revving sound was just the engine cooling fans, and not the compressor. I was looking at the compressor as the AC was running. All the belts and everything seem to be moving (with no change whether or not the AC button is pressed). Oh well.

If the AC has been off for a while, the high side and the low side will come to equilibrium at the same value... the low side should be around 25 when the A/C is on.

You should have a low-pressure cutoff switch somewhere in there.. if you have an accumulator type system it will probably be on the accumulator. What this switch does is if it senses that the pressure is too low in the system, the switch will open electrically and cause the compressor to not run. It sounds like your freon charge is ok, so it's possible that switch is faulty. You can test that by turning the A/C controls in the car to max while the car is running and jump that switch... if the compressor starts to operate, then it is likely that the switch is faulty.
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Old 08-12-2004, 01:03 AM   #63
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The best way to test a switch like that is to make sure you have enough pressure to close the switch, and take an OHMs reading.
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Old 08-12-2004, 09:47 PM   #64
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jumpering the A/C dual pressure switch does nothing for the compressor. But it does cause the two fans to run without shutting off intermitently as before.

DodgeRida, do you mean ohms reading across the switch terminals? I'm not sure how else to make sure I have enough pressure. I actually tried measuring the pressure on the high side, but the freon coming out from there is a LOT cooler! Almost painful to the touch. The stuff coming out from the low side was pretty much just air that had a light scent to it.
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Old 08-12-2004, 10:15 PM   #65
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DodgeRida, do you mean ohms reading across the switch terminals?


Yes. This switch should be good though, if it wasn't you shouldnt have had voltage at the coilside of the a/c relay. Test it anyway, because I've seen crazy things happen before.
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Old 08-12-2004, 10:35 PM   #66
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990 ohms or something like that (that's of course with the switch completely out; that's the only way I could measure the resistance reading).

But get this. With the switch out and the AC running, the AC light actually stays on without turning off and blinking like before. The car seems to pulsate a little more, but still does not cool.

I think the compressor might just be running the entire time. As in it's not shutting off at all. Is that possible, or am I just not knowing which one is the compressor pulley and what not?
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Old 08-12-2004, 10:52 PM   #67
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Originally Posted by JaneiR36
990 ohms or something like that (that's of course with the switch completely out; that's the only way I could measure the resistance reading).

But get this. With the switch out and the AC running, the AC light actually stays on without turning off and blinking like before. The car seems to pulsate a little more, but still does not cool.

I think the compressor might just be running the entire time. As in it's not shutting off at all. Is that possible, or am I just not knowing which one is the compressor pulley and what not?

The switch needs to be installed when you test it. But I'm assuming when you say "thats with the switch completely out" you ment jyst the harness (wires) off the top of the switch. because if the switch is out, it's obviously going to be open. But what you checking for is for it to be closed, which it will do (or should do) when you have proper pressure.

So the compressor may have been on the whole time? If the compressor is on, the entire front of the thing will be spinning. Nothing up front will be stationary.
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Old 08-12-2004, 11:25 PM   #68
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You can try measuring the voltage across those two terminals, with the switch in and enough pressure in the system. If the switch is open, as it should be, there should be no voltage difference between the two terminals.

It sounds like there may be a control problem somewhere, or some switch that it detecting something wrong and shutting off the compressor. I don't think the compressor is on all the time because there exist a variety of switches wired in series just to shut off the compressor. If the compressor is on all the time, then we need to measure the low side and high side pressures. The bad news is if the compressor is engaging and the low side and high side pressures are about the same, 80-100psi, then the compressor is probably shot.

Also check and see if there is a temperature difference between the two pipes going into the firewall from the engine compartment. Check to see if there is a temperature difference between the inlet and the outlet of the condenser. The inlet of the condensor should be the line that goes from the compressor up to the top of the front of the car, and the outlet should come out of the bottom of the condensor.

Do you know if your system has a receiver/dryer or an accumulator? A receiver/dryer is usually located after the outlet of the condensor before the firewall, which is on the highside or liquid side of the system. An accumulator will be on the lowside, and it will probably be where the lowside port is located.
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Old 08-13-2004, 12:45 AM   #69
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I'll try to get the high side readings (already mentioned some difficulty I was having getting the pressure on the high side; is it safe to press the little thingie against the high pressure opening when the freon is so cold and seems to be at such a high pressure?)

Yeah the switch is alright. Voltage at both terminals is like 14.something, even without the AC on. When the AC comes on, it drops to like 13.something.

Dodge, yeah, all the visible parts of the compressor / pulley appear to be moving.

kanato, gimme at least a day to research your additional questions (took me 10 good minutes to confirm the location of the pressure switch), and when you say temperature, do you mean to the touch, or actually take a temperature reading?
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Old 08-13-2004, 01:21 AM   #70
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Originally Posted by JaneiR36
I'll try to get the high side readings (already mentioned some difficulty I was having getting the pressure on the high side; is it safe to press the little thingie against the high pressure opening when the freon is so cold and seems to be at such a high pressure?)

Yeah the switch is alright. Voltage at both terminals is like 14.something, even without the AC on. When the AC comes on, it drops to like 13.something.

Dodge, yeah, all the visible parts of the compressor / pulley appear to be moving.

kanato, gimme at least a day to research your additional questions (took me 10 good minutes to confirm the location of the pressure switch), and when you say temperature, do you mean to the touch, or actually take a temperature reading?

You really need a set of manifold gauges to read the high side. The connector should be a bit larger than the lowside port. I think you can probably rent a set of gauges at autozone. But let's check the other things first.

The temperature differences should be fairly large, under normal operation, so you could probably do it by touch. But if you have a thermometer handy, that would be better.

Also, I noticed that you said that the A/C light was blinking? Somewhere, there should be some reference as to how to turn that into useful information. But I'm not coming up with much on a Google search. Do you have any owner's/repair manuals that might shed some light on that?
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Old 08-13-2004, 04:27 AM   #71
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Originally Posted by JaneiR36
While I'm waiting for responses on my light bulb problems, I may as well post about my A/C. It doesn't blow cold air. I've tried topping off the freon, but it doesn't seem to be sucking anything from the can even with the vehicle on and the A/C on full blast. My sister once had it checked out, and they said it would cost about $300 to fix (I have no details on what's wrong, sorry). I'd like to confirm this for myself without getting it professionally tested again. If you have any ideas for dianosing the problems, please let me know. I will need very simplified instructions because I'm a total beginner in this.

Car: Toyota Camry '96 LE, Automatic shift, 4 cylinders.

PS: I'm having difficulty searching for past A/C topics, because it says "A/C" is too short to be included in a search, and of course people tend not to write out "air conditioner" in their posts (only found four topics with that).

Oh, I've checked the two A/C fuses located at the passenger side kick panel. They are intact.
petethegreek---First of all , without a set of guages there is no way of knowing what high and low side pressure is. If you know what the pressure readings are then you generally know what direction to go in. Sight unseen , it is almost impossible to diagnose a symptom without any info . All these suggestions that you have recieved are just educated guesses.You cant even begin to imagine how many diff. problems can cause your symptoms. Even though you don't want to spend the $ to have it diagnosed , that is the best way. And by the way , you must be certified to handle refrigerant. Oh, and one more thing, you mentioned earlier that you " topped off the freon" . How do you know how low it was and how much you added? The only way of knowing this is with a scale under your refrigerant tank, or with a premeasured amount, or by monitoring pressures as you fill, and if you had to add that means that there is a leak, if there is a leak that means there is air and contaminants in the system. As you can see there is alot to an a/c system , and thats just the tip of the ice-berg. Bottom line, TAKE IT TO A CERTIFIED REPAIR FACILITY AND HAVE IT DONE RIGHT , " ONCE "
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Old 08-13-2004, 04:51 AM   #72
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Originally Posted by petethegreek
petethegreek---First of all , without a set of guages there is no way of knowing what high and low side pressure is. If you know what the pressure readings are then you generally know what direction to go in. Sight unseen , it is almost impossible to diagnose a symptom without any info . All these suggestions that you have recieved are just educated guesses.You cant even begin to imagine how many diff. problems can cause your symptoms. Even though you don't want to spend the $ to have it diagnosed , that is the best way. And by the way , you must be certified to handle refrigerant. Oh, and one more thing, you mentioned earlier that you " topped off the freon" . How do you know how low it was and how much you added? The only way of knowing this is with a scale under your refrigerant tank, or with a premeasured amount, or by monitoring pressures as you fill, and if you had to add that means that there is a leak, if there is a leak that means there is air and contaminants in the system. As you can see there is alot to an a/c system , and thats just the tip of the ice-berg. Bottom line, TAKE IT TO A CERTIFIED REPAIR FACILITY AND HAVE IT DONE RIGHT , " ONCE "

You could probably say most of this about anything anyone posts on the Repairs & Maintenance forum. Of course if someone hasn't looked at the car they're going to have a hard time giving more than an educated guess. But I think what we're trying to do is at least narrow the scope of the problem down. There are some very complicated things that could be wrong which require expensive equipment to fix (ie. compressor failure requiring refrigerant recovery & evac in order to replace) and some very simple things that could be wrong (ie. relay switch), stuff which does not require openning the refrigerant system up. If she has to take it to a mechanic, it'd be nice to know what kind of things the problem could be so there's no rip-off involved, because some mechanics can be quite unscrupulous.
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Old 08-13-2004, 11:07 AM   #73
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Unfortunately, the manual I have is electrical only. (Turns out the whole thing wasn't $118, that was just for the mechanical repair manual, there was another one for electrical, and a third for automatic transmission or something....... and since I needed wiring diagrams............)

What they did mention in this one, though, is that the AC mag relay switch should be closed with the ignition, blower, and AC switches on. So far, the first two are definitely working. The third seems to be working from our readings, but something does get shut off.

They've also mentioned that the dual pressure switch would be "open with pressure 30 psi or above 384 psi." What does that mean, really? I'll look into renting the manifold gauges, but I'm already getting the general impression that the high side pressure is much higher than the low side. Maybe the estimation should help a little? The pressures don't seem to have equalized as originally thought.

petethegreek, while your suggestion is by no means original (yes, even on this thread!), I do seem to be nearing the end of my rope. If I don't have this diagnosed and fixed when it starts to cool off, I'll either shut down the project till next summer or just get it fixed professionally. Happy?
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Old 08-13-2004, 05:46 PM   #74
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Quote:
Originally Posted by JaneiR36
Unfortunately, the manual I have is electrical only. (Turns out the whole thing wasn't $118, that was just for the mechanical repair manual, there was another one for electrical, and a third for automatic transmission or something....... and since I needed wiring diagrams............)

What they did mention in this one, though, is that the AC mag relay switch should be closed with the ignition, blower, and AC switches on. So far, the first two are definitely working. The third seems to be working from our readings, but something does get shut off.

They've also mentioned that the dual pressure switch would be "open with pressure 30 psi or above 384 psi." What does that mean, really? I'll look into renting the manifold gauges, but I'm already getting the general impression that the high side pressure is much higher than the low side. Maybe the estimation should help a little? The pressures don't seem to have equalized as originally thought.

petethegreek, while your suggestion is by no means original (yes, even on this thread!), I do seem to be nearing the end of my rope. If I don't have this diagnosed and fixed when it starts to cool off, I'll either shut down the project till next summer or just get it fixed professionally. Happy?
Obviously high side pressure is high and low side pressure is low, that's where they get their names.


Quote:
"open with pressure 30 psi or above 384 psi." What does that mean, really?

OK - it's a switch as you know. If a switch is "open" it is off. If a switch is "closed" it is on. So if the pressure drops below 30PSI the switch will open (go off) or if it reaches pressures above 384 is will go open. Anything in between and the switch will be closed (on)

petethegreek, it is recommended R134A refridgerant be handled and used by a licenced person, but is not enforced nor is it the law. After all, R134A is used to blow out the keyboard your using which you can buy at any office supply shop. Since when do service shops do jobs "right"? If people never learn anything they will get ripped off their entire lives. I'd hate to pay a mechanic for every problem I had.
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Old 08-13-2004, 06:27 PM   #75
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Originally Posted by DodgeRida67

petethegreek, it is recommended R134A refridgerant be handled and used by a licenced person, but is not enforced nor is it the law. After all, R134A is used to blow out the keyboard your using which you can buy at any office supply shop. Since when do service shops do jobs "right"? If people never learn anything they will get ripped off their entire lives. I'd hate to pay a mechanic for every problem I had.

From looking at http://www.epa.gov/oar/caa/caa609.txt, it seems that it's required by law that the person handling the refrigerant be certified when "servicing .. for consideration," that is, being paid for the work. If they were really serious about making even DIY type people be certified, then you couldn't go into walmart and buy cans of R134a whenever you like. And I've had quite a few service shops screw things up. I totally agree with DodgeRida67 here.

Quote:
Originally Posted by JaneiR36
I'll look into renting the manifold gauges, but I'm already getting the general impression that the high side pressure is much higher than the low side.

Under normal operation, the low side should probably be about 20-30psig and the high side should probably be around 200psig. Since we don't seem to have normal operation, it's something worth checking into. But check the temperatures first, since it's easier.
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