95 4runner a/c compressor runs all the time!
07-03-2013, 03:01 PM
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95 4runner a/c compressor runs all the time!
Hi guys, first post.
I did a bunch of searching and I can't find anything related on the forums or in the FAQ, so, here goes:
The A/C compressor on my 95 4runner sr5 3.slow runs all the time and robs roughly half my power and absolutely murders my gas mileage!
The A/C blows cold, works perfectly fine, no problems. The compressor on the other hand will turn off for about 10 minutes of an hour plus long drive! Living way up in the mountains makes this rather problematic when trying to climb steep grades, not to mention the hit on my already crappy gas mileage.
Since I'm largely of the "if it ain't broke, don't fix it" type of mind, and since everything else about the system is fine I'd like to be able to wire in a kill switch for the electric clutch on the compressor to keep it from turning on unless I let it.
Of course, I'm open to any other suggestions that might fix it as well as long as I'm not looking at replacing anything major.
Any ideas?
Thanks in advance.
I did a bunch of searching and I can't find anything related on the forums or in the FAQ, so, here goes:
The A/C compressor on my 95 4runner sr5 3.slow runs all the time and robs roughly half my power and absolutely murders my gas mileage!
The A/C blows cold, works perfectly fine, no problems. The compressor on the other hand will turn off for about 10 minutes of an hour plus long drive! Living way up in the mountains makes this rather problematic when trying to climb steep grades, not to mention the hit on my already crappy gas mileage.
Since I'm largely of the "if it ain't broke, don't fix it" type of mind, and since everything else about the system is fine I'd like to be able to wire in a kill switch for the electric clutch on the compressor to keep it from turning on unless I let it.
Of course, I'm open to any other suggestions that might fix it as well as long as I'm not looking at replacing anything major.
Any ideas?
Thanks in advance.
07-03-2013, 03:34 PM
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Hmm, forgot to mention, it runs even with the switch off and the blower turned off. It runs all the time, pretty much.
Usually, it's supposed to turn on once in a while, even with the A/C off, to maintain system pressure, but mine's almost always running. It's a rare day that it's not.
Usually, it's supposed to turn on once in a while, even with the A/C off, to maintain system pressure, but mine's almost always running. It's a rare day that it's not.
07-03-2013, 07:29 PM
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Are you sure it runs with the blower switch off? Unless the blower relay is stuck, there's no power source to the AC system with the blower turned off. It is possible for the compressor to run with the AC switch off if the AC amplifier has failed.
Pull out the glove box (easy, just 5 screws, 2 underneath and 3 inside top with the door open), and then pull the AC fuse (10A) and the 40A heater fuse. The fuses are in a white receptacle on the upper right of the area behind the glove box. If the AC fuse doesn't stop the compressor, you likely have a bad AC amplifier (black box under the dash behind the glove box.) If the blower fuse doesn't stop it, someone has added an extra wiring path to keep the compressor running.
Pull out the glove box (easy, just 5 screws, 2 underneath and 3 inside top with the door open), and then pull the AC fuse (10A) and the 40A heater fuse. The fuses are in a white receptacle on the upper right of the area behind the glove box. If the AC fuse doesn't stop the compressor, you likely have a bad AC amplifier (black box under the dash behind the glove box.) If the blower fuse doesn't stop it, someone has added an extra wiring path to keep the compressor running.
Last edited by RJR; 07-05-2013 at 10:36 AM.
07-04-2013, 01:47 AM
#5
Most times when a clutch goes bad it will not pull in.
something is not right here.
Putting a switch in it would need to be in the circuit before all the pressure switches .
Without them it would just be a matter of time till you flipped the switch at the wrong time .
To high of head pressure breaking the belt maybe the compressor .
Belt gets pulled into the other belts making a big mess.
I have never heard of a compressor coming on without the switches being on. After all it is a charged system
something is not right here.
Putting a switch in it would need to be in the circuit before all the pressure switches .
Without them it would just be a matter of time till you flipped the switch at the wrong time .
To high of head pressure breaking the belt maybe the compressor .
Belt gets pulled into the other belts making a big mess.
I have never heard of a compressor coming on without the switches being on. After all it is a charged system
07-04-2013, 08:34 AM
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Are you sure it runs with the blower switch off? Unless the blower relay is stuck, there's no power source to the AC system with the blower turned off. It is possible for the compressor to run with the AC switch off if the AC amplifier has failed.
Pull out the glove box (easy, just 5 screws, 2 underneath and 3 inside top with the door open), and then pull the AC fuse (10A) and the 40A heater fuse. The fuses are in a white receptacle on the upper right of the area behind the glove box. If the AC fuse doesn't stop the compressor, you likely have a bad AC amplifier (black box under the dash behind the glove box.) If the blower fuse doesn't stop it, someone has added an extra wiring path to keep the compressor running.
I've tried to attach a .pdf of the AC wiring diagram. Don't know if it worked, however.
Pull out the glove box (easy, just 5 screws, 2 underneath and 3 inside top with the door open), and then pull the AC fuse (10A) and the 40A heater fuse. The fuses are in a white receptacle on the upper right of the area behind the glove box. If the AC fuse doesn't stop the compressor, you likely have a bad AC amplifier (black box under the dash behind the glove box.) If the blower fuse doesn't stop it, someone has added an extra wiring path to keep the compressor running.
I've tried to attach a .pdf of the AC wiring diagram. Don't know if it worked, however.
To give a little more information, it comes on and runs almost the entire time. It will turn off once in a while, but only for a few minutes then it will come right back on with the A/C switch off and the blower motor control in the off position. It's loud too. Ever hear an air compressor for the brake system on a large diesel truck? It sounds just like that.
Edited to add: Yes, the .pdf worked, thanks again!
Last edited by CandleJack; 07-04-2013 at 08:53 AM.
07-04-2013, 08:36 AM
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Most times when a clutch goes bad it will not pull in.
something is not right here.
Putting a switch in it would need to be in the circuit before all the pressure switches .
Without them it would just be a matter of time till you flipped the switch at the wrong time .
To high of head pressure breaking the belt maybe the compressor .
Belt gets pulled into the other belts making a big mess.
I have never heard of a compressor coming on without the switches being on. After all it is a charged system
something is not right here.
Putting a switch in it would need to be in the circuit before all the pressure switches .
Without them it would just be a matter of time till you flipped the switch at the wrong time .
To high of head pressure breaking the belt maybe the compressor .
Belt gets pulled into the other belts making a big mess.
I have never heard of a compressor coming on without the switches being on. After all it is a charged system
So I guess there's no cheating there. I'm gonna have to diagnose the actual problem and fix it. I'd really hate to have it go 'splodey on me on the road. I travel for a living so that would be really bad if that happened in the middle of nowhere on the highway.
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07-04-2013, 01:28 PM
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Well, I pulled the recommended fuses (both at the same time) and it still kept running as usual. I wasn't able to find any extraneous wiring to the compressor, so I'm betting on the AC amplifier. We'll see what happens when I replace that.
ETA: Whoops, working on finding a link to the right part.
Thanks.
ETA: Whoops, working on finding a link to the right part.
Thanks.
Last edited by CandleJack; 07-04-2013 at 01:31 PM.
07-04-2013, 03:45 PM
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There are a couple of mystery (at least to me) connections between the ECU and the AC amplifier, labeled ACV, ACT, and AC. According to the manual, AC is an input to the ECU, so cannot provide power to the AC amplifier. It's possible that the ACV or ACT terminal can apply power and turn on the compressor independently of the AC switch and blower circuit, for defrosting or just to run it every so often. You should probably check what's going on with those two connections.
You can disconnect the wires from the AC amplifier to the compressor, by opening connector IG1 which is at the top behind the glove box. That should remove any possibility of power to the compressor clutch unless someone has jumpered in a wire directly to the compressor. If it still runs with that disconnected you've definitely got a stuck clutch or an extra wire somewhere.
The fact that the compressor is loud indicates it's probably been running under conditions when it shouldn't be, such as too high or too low a pressure, etc. Be prepared to replace it once you get this figured out.
Ron
You can disconnect the wires from the AC amplifier to the compressor, by opening connector IG1 which is at the top behind the glove box. That should remove any possibility of power to the compressor clutch unless someone has jumpered in a wire directly to the compressor. If it still runs with that disconnected you've definitely got a stuck clutch or an extra wire somewhere.
The fact that the compressor is loud indicates it's probably been running under conditions when it shouldn't be, such as too high or too low a pressure, etc. Be prepared to replace it once you get this figured out.
Ron
07-05-2013, 10:21 AM
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Awesome, I'll try that this weekend.
I was thinking the same thing about the noise. It the compressor is definitely dragging hard and is probably over charging the system which has me worried. I'm surprised nothing has blown out yet.
Again, thank you for looking into this for me.
I was thinking the same thing about the noise. It the compressor is definitely dragging hard and is probably over charging the system which has me worried. I'm surprised nothing has blown out yet.
Again, thank you for looking into this for me.
07-05-2013, 08:28 PM
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There's no indication in the '94 FSM or wiring diagram that an RPM control exists. I think that might be an adjustment that existed in earlier models, but was dropped by '94. In addition, while a faulty RPM sensor could certainly prevent the compressor from running, it couldn't cause it to run continuously, in the absence of some other fault.
07-06-2013, 02:49 PM
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Punchy: I'll give the power wire on the compressor a try if all else fails.
Going to go disconnect the amplifier now and give it a test run. Haven't had time yet since I was replacing my rear springs, now that that's done, we'll see how this goes.
Going to go disconnect the amplifier now and give it a test run. Haven't had time yet since I was replacing my rear springs, now that that's done, we'll see how this goes.
07-06-2013, 04:19 PM
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Okay. I'm not sure I did this right, but, first I disconnected the one next to the awesomely drawn red arrow and the compressor ran for about 20 seconds, shut off then came back on in about five minutes. Reconnected it and discoed the one near the green arrow, exact same thing.
So, I take it both of these are wrong and I need to disco the top connector?
I didn't try it because I can't get it undone.
So, I take it both of these are wrong and I need to disco the top connector?
I didn't try it because I can't get it undone.
07-07-2013, 01:28 PM
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Yeah, I'm going to take a crack an unwiring the compressor. This is getting to be a pain. If that doesn't do it I guess I'll just take the computer technician approac: start replacing things until it works right again 
07-07-2013, 05:32 PM
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Got the other connector out, still no joy. I think it's time to get creative, if that fails. I'll just start replacing parts until it works right again.
I'm thinking pressure sensors might be a good place to start.
I'm thinking pressure sensors might be a good place to start.
07-07-2013, 06:42 PM
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The third connector that you removed (not the ones with the arrows) is the correct one. The black and white wire in that connector goes directly to the compressor. With the connector out and with the engine running, check the voltage on the black and white wire (on the free end of the connector, not the end attached to the bracket). If it's zero your clutch is stuck. If it's 12V you've got an extra rogue wire going to the compressor which is powering it up.
Don't go after the pressure switches - by pulling the A/C and blower fuses you've already proved that the upstream switches are not the source of turn-on current to the compressor clutch. At this point you've either got a bad compressor clutch or a rogue wire going directly to it. Either way, you're going to have to get a look at the compressor itself, which probably means pulling the power steering pump (not as bad a job as it looks. Suck out the fluid with a turkey baster, remove the battery, loosen the bracket to take off the belt, and remove the mounting bolts and it should move out of the way far enough so you can get a good look at the compressor. If you do have to remove the power steering hoses, a few quick burps with an impact wrench are helpful in removing the high pressure banjo fitting on the side of the pump.)
rworegon's point about making sure it's the AC compressor that's making all the noise is a good one. It'd be a shame to be doing all this work chasing the wrong problem.
Don't go after the pressure switches - by pulling the A/C and blower fuses you've already proved that the upstream switches are not the source of turn-on current to the compressor clutch. At this point you've either got a bad compressor clutch or a rogue wire going directly to it. Either way, you're going to have to get a look at the compressor itself, which probably means pulling the power steering pump (not as bad a job as it looks. Suck out the fluid with a turkey baster, remove the battery, loosen the bracket to take off the belt, and remove the mounting bolts and it should move out of the way far enough so you can get a good look at the compressor. If you do have to remove the power steering hoses, a few quick burps with an impact wrench are helpful in removing the high pressure banjo fitting on the side of the pump.)
rworegon's point about making sure it's the AC compressor that's making all the noise is a good one. It'd be a shame to be doing all this work chasing the wrong problem.
Last edited by RJR; 07-07-2013 at 06:51 PM.
