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AC idle up help

Old 06-27-2018, 02:58 AM
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AC idle up help

Okay so I've searched my behind off and some are having my issues but I can't find any solutions to my AC problem. Truck is a 94 22re. The AC works fine driving down the road, but once stopped it won't idle up. Here is what I know or think I know. The amplifier knob controls at what RPM the compressor kicks on. The VSV is just a valve that opens to let vacuum in or not which causes the idle to raise. The AC idle screw controls the amount of vacuum let in to VSV thus what RPM the engine idles up to.
1. My amplifier works fine I've turned it both ways and the compressor will kick on or off accordingly.
2. VSV makes clicking noise so I assume its working and I've tried several VSVs with no idle up no matter how much I unscrew the idle screw.
3. I've connected the two hoses to VSV together (bypassing the VSV) and still no idle up unless I screw in the idle screw all the way shut then unscrew it again to desired idle. As long as I keep the AC running it stays idled up, but if I kill the engine or AC, even with hoses still connected together (VSV still bypassed) the idle will go back down unless I screw the idle screw all the way in and back out again.
I'm at a loss and have no idea where to go. I've even taken the idle valve off and cleaned it and put it back on. Checked hoses to see if they are plugged and they are fine. Please help!!!!
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Old 06-27-2018, 03:51 AM
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Hmmmm...possible vacuum leak else where in the system or a cracked fitting? Did you try a different A/C idle screw?
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Old 06-27-2018, 09:16 AM
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Is your warm idle set properly? How about some pictures and maybe a diagram of how your vac lines are routed? I've never really heard of anyone's idle up diaphragm being bad, but who knows maybe it is, I'm more inclined to think your vac lines are just not routed correctly and if we could see some pictures, it might help.
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Old 06-27-2018, 11:49 AM
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Originally Posted by BigBluePile View Post
Hmmmm...possible vacuum leak else where in the system or a cracked fitting? Did you try a different A/C idle screw?
i donít think itís a vacuum leak and Iíve checked for that. I havenít tried a new idle screw. I think i May try and find the valve that idle screw is in and try that.
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Old 06-27-2018, 11:51 AM
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Originally Posted by coryc85 View Post
Is your warm idle set properly? How about some pictures and maybe a diagram of how your vac lines are routed? I've never really heard of anyone's idle up diaphragm being bad, but who knows maybe it is, I'm more inclined to think your vac lines are just not routed correctly and if we could see some pictures, it might help.
yes idle is set at about 850 to 900 without AC on. I know itís routed right. There is a diagram under the hood as well as Iíve looked it up in service manual. This has gotten me so confused.
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Old 06-27-2018, 03:51 PM
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If connecting the port on the plenum directly to the unmetered air from the air box doesn't raise the idle, then I would first suspect that the port on the plenum is blocked.
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Old 06-28-2018, 02:38 AM
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Originally Posted by scope103 View Post
If connecting the port on the plenum directly to the unmetered air from the air box doesn't raise the idle, then I would first suspect that the port on the plenum is blocked.
yes sir i thought that as well. Iíve took it off now twice and cleaned it. Itíll raise the rpm but only after i screw in the idle all the way then back out. If i kill the AC and start it up again then it wonít raise rpm anymore and i have to repeat the screwing in and out. This has gotten me so confused. I thought about buying another idle valve with the idle screw but theyíre discontinued and i canít even find a used one.
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Old 07-02-2018, 01:24 PM
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I’m having a problem very similar to this. I’m curious of the fix.
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Old 07-05-2018, 03:17 AM
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Next AC problem. So the AC had been working fine except the idle up issue. Yesterday the compressor started acting up. It would kick off for a good while then come back on. Checked Freon and it was fine. Today it wonít come on at all. No power to compressor. If i jump 12v to compressor it comes on and cools just fine. Any ideas? Low pressure switch?
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Old 07-05-2018, 10:13 AM
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Could also be the high side sensor switch as well!!....gotta remember that the high sides function is to tell the ECU to break ground to the compressor clutch to disengage it, if the head pressure gets too high!!.....Just as the low pressure side switch does the same if the freon or pressure goes too low to protect your compressor from burning up!!....the fact that you can activate the clutch by jumpering eliminates the clutch being faulty!!...Question to YOU??... did you jumper 12 volts or induce ground to the compressor clutch??...reason Im asking is because on my Yota, 12 volts is always present at the clutch, and the clutch engages when ground is induced thru the ECU, so keep the ground in mind before proceeding with these other suggestions!!....Chances are you most likely have a pressure sensor switch malfunction!!... quirky compressor cycling as you described usually indicates a switch going bad before total failure!! The very last fault I would even consider is a faulty ECU, which if it leads to that would most likely be a pin connection to or from the ECU cannon or connector plug, instead of the electronics itself of the ECU!!....Ive bypassed pressure switch,s before, to check them!!...but if you can rig a closed position from the switch connector to the ECU, and the clutch engages each time you try it, then you've found your BAD pressure switch!!...The HP switch is normally in a closed switch position....If the head pressure gets TOO HIGH, It will open at a preset pressure setting, telling the ECU to shut down/disengage the compressor clutch. If it is stuck in the open position, it will tell the ECU to keep the clutch disengaged forever, until it gets the correct voltage again to induce ground/ or voltage back to the A/C clutch!!...Hope this helps you out!!
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Old 07-05-2018, 11:59 AM
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Originally Posted by Dseldown View Post
Could also be the high side sensor switch as well!!....gotta remember that the high sides function is to tell the ECU to break ground to the compressor clutch to disengage it, if the head pressure gets too high!!.....Just as the low pressure side switch does the same if the freon or pressure goes too low to protect your compressor from burning up!!....the fact that you can activate the clutch by jumpering eliminates the clutch being faulty!!...Question to YOU??... did you jumper 12 volts or induce ground to the compressor clutch??...reason Im asking is because on my Yota, 12 volts is always present at the clutch, and the clutch engages when ground is induced thru the ECU, so keep the ground in mind before proceeding with these other suggestions!!....Chances are you most likely have a pressure sensor switch malfunction!!... quirky compressor cycling as you described usually indicates a switch going bad before total failure!! The very last fault I would even consider is a faulty ECU, which if it leads to that would most likely be a pin connection to or from the ECU cannon or connector plug, instead of the electronics itself of the ECU!!....Ive bypassed pressure switch,s before, to check them!!...but if you can rig a closed position from the switch connector to the ECU, and the clutch engages each time you try it, then you've found your BAD pressure switch!!...The HP switch is normally in a closed switch position....If the head pressure gets TOO HIGH, It will open at a preset pressure setting, telling the ECU to shut down/disengage the compressor clutch. If it is stuck in the open position, it will tell the ECU to keep the clutch disengaged forever, until it gets the correct voltage again to induce ground/ or voltage back to the A/C clutch!!...Hope this helps you out!!
I pulled the plug on the compressor and turned AC on. Tested the plug and no power to it. Then i ran 12v from battery to compressor and it came on. Where is the high pressure switch located. I know the low pressure is in the evaporator box but canít seem to locate the high pressure side. I read a thread earlier on how to jump the low pressure side and see if that starts it. Iím going to try that later. Iíve also read where they talk about a AC breaker. Where is that? Is that the relay behind the glove box?
thanks for the reply

Last edited by an1176; 07-05-2018 at 01:31 PM.
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Old 07-05-2018, 06:07 PM
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Update...
idle up issue fixed!!! Finally something is going my way. Lol. It was the idle up bypass valve that has the idle screw. I found only one used one on eBay and none new.

Compressor not coming on. I checked fuses again and i tried jumping the pressure switch nothing. Behind the glove box i have one plug that has never been plugged into anything. No idea what itís for. When you press the ac button it gets power. I jumped it and BAM compressor kicked on. Itís probab not what Iím supposed to do but i left jumped and i have cold air again.
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Old 07-05-2018, 07:31 PM
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Can you take a picture of what it was that you jumped? It seems kind of strange that you had a working AC system and then nothing at all, and that jumping something that wasn't the pressure switch made it work again.
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Old 07-06-2018, 11:20 AM
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Originally Posted by an1176 View Post

I pulled the plug on the compressor and turned AC on. Tested the plug and no power to it. Then i ran 12v from battery to compressor and it came on. Where is the high pressure switch located. I know the low pressure is in the evaporator box but canít seem to locate the high pressure side. I read a thread earlier on how to jump the low pressure side and see if that starts it. Iím going to try that later. Iíve also read where they talk about a AC breaker. Where is that? Is that the relay behind the glove box?
thanks for the reply
Ok I thought that you already did that!!...jumpering a direct connection to the clutch to determine that its OK!!....What I was saying for you to do is separate the high side connector switch and jumper across the connector to see if the clutch engages....do the same on the low side if you get no results from the HSide....the high side switch can be found by tracing the little line, when you come to it you'll see it immediately its a 2 pin connection!!....The low side or suction side of your system is the fatter diameter of the 2 lines, do the same to locate the low pressure side switch and attempt to jumper across it to simulate a closed switch to the ECU!!...if 1 of these 2 switches are bad, you'll see the clutch engage immediately pumping freon again, if you remove the jumper and the clutch disengages and then engages again upon re-jumpering...you've found your faulty sensor switch!!....I assume you have a volt meter, turn on your AC system to normal mode with engine running and then check to see if you have 12 VDC coming to the compressor clutch plug from the ECU, connect your black lead to chassis ground and with the red lead touch each pin separately to determine if in fact you have VDC to the clutch connector AT ALL!!....If you don't then it probably means your ECU is being told to not supply VDC because of one of the 2 pressure sensor switches being faulty/stuck in a open position!!....next thing to do is look real closely at the ground connection of the clutch to make sure its healthy, not corroded, broken lead. loose ETC!!...Remember that current cannot flow W/O a good source of ground to complete the circuit!!...Ahhh Im not sure where or if theres a A/C breaker, but it probably would be in the engine compartment as a bulky relay along with the other relays, as the fuse panel box is separate from that and doesn't host any relays, however I don't own a 4 runner so don't flame me if Im wrong!!....but all the other advice is spot on to determine what the true cause is of why your clutch wont engage...again you said that before it went totally bad it was cycling/acting up weird, and again thats usually textbook example of a faulty pressure switch going bad, because its flipping between open and closed at the wrong/but correct pressures!!
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Old 07-06-2018, 11:34 AM
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Originally Posted by mholme View Post
Can you take a picture of what it was that you jumped? It seems kind of strange that you had a working AC system and then nothing at all, and that jumping something that wasn't the pressure switch made it work again.
No thats not strange at all!!....because he eliminated the ECU to see if the clutch would engage!!....If the clutch is good, it'll engage immediately upon jumpering it!!...as long as the compressor is pumping freon, the sysytem will start to cool if the rest of the system is healthy as normal!!...But its not a repair!!.... as you would risk the head building too high a head pressure and blowing the seal on the compressor or worst!!.... Ive done this before [jumpering the compressor clutch] for short periods of time to purge air outta of a system, when we didn't have a vacuum pump to do it correctly!!.... and took a field repair chance!!...meaning NOT TOO LONG, to avoid burning up the compressor, to try and get a system to charge and go for awhile or just 1 more summer on something that we didn't care about that much about...meaning low value cars or trucks!!
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Old 07-06-2018, 03:32 PM
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Originally Posted by mholme View Post
Can you take a picture of what it was that you jumped? It seems kind of strange that you had a working AC system and then nothing at all, and that jumping something that wasn't the pressure switch made it work again.
The plug with the green wire going into it. I put the green wire in because i added an electric fan. By the way with the electric fan my mpg went up 2.5 mpg. That plug has never been plugged into anything. Jumping it the ac started working again or compressor started working.
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Old 07-06-2018, 03:44 PM
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Originally Posted by Dseldown View Post
Ok I thought that you already did that!!...jumpering a direct connection to the clutch to determine that its OK!!....What I was saying for you to do is separate the high side connector switch and jumper across the connector to see if the clutch engages....do the same on the low side if you get no results from the HSide....the high side switch can be found by tracing the little line, when you come to it you'll see it immediately its a 2 pin connection!!....The low side or suction side of your system is the fatter diameter of the 2 lines, do the same to locate the low pressure side switch and attempt to jumper across it to simulate a closed switch to the ECU!!...if 1 of these 2 switches are bad, you'll see the clutch engage immediately pumping freon again, if you remove the jumper and the clutch disengages and then engages again upon re-jumpering...you've found your faulty sensor switch!!....I assume you have a volt meter, turn on your AC system to normal mode with engine running and then check to see if you have 12 VDC coming to the compressor clutch plug from the ECU, connect your black lead to chassis ground and with the red lead touch each pin separately to determine if in fact you have VDC to the clutch connector AT ALL!!....If you don't then it probably means your ECU is being told to not supply VDC because of one of the 2 pressure sensor switches being faulty/stuck in a open position!!....next thing to do is look real closely at the ground connection of the clutch to make sure its healthy, not corroded, broken lead. loose ETC!!...Remember that current cannot flow W/O a good source of ground to complete the circuit!!...Ahhh Im not sure where or if theres a A/C breaker, but it probably would be in the engine compartment as a bulky relay along with the other relays, as the fuse panel box is separate from that and doesn't host any relays, however I don't own a 4 runner so don't flame me if Im wrong!!....but all the other advice is spot on to determine what the true cause is of why your clutch wont engage...again you said that before it went totally bad it was cycling/acting up weird, and again thats usually textbook example of a faulty pressure switch going bad, because its flipping between open and closed at the wrong/but correct pressures!!
Iíve researched my butt off and i can not find a high pressure switch. The low pressure switch is inside the evaporator box. To get to it Iíll have to let all the Freon out and pull the box. I was hoping not to do that but i was prepared to. Funny thing is last week everything worked fine except the idle up, which i fixed yesterday. I added an electric cooling fan, doing away with the fan clutch on the water pump. Soon as i did that the ac started acting up. It would ingage and disingage, until finally nothing. Jumping the plug that i put a picture of ingaged the compressor again. I drove it today and it worked fine and ac blew cold and engine idled up. The electric fan has to be connected to the ac somewhere so that soon as your ac is turned on the fan comes on no matter what your coolant temp is. Iím wondering by doing this i didnít screw something up. The fan is jumped at the ac fuse currently. Thanks for the help.
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Old 07-06-2018, 04:46 PM
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Originally Posted by an1176 View Post

Iíve researched my butt off and i can not find a high pressure switch. The low pressure switch is inside the evaporator box. To get to it Iíll have to let all the Freon out and pull the box. I was hoping not to do that but i was prepared to. Funny thing is last week everything worked fine except the idle up, which i fixed yesterday. I added an electric cooling fan, doing away with the fan clutch on the water pump. Soon as i did that the ac started acting up. It would ingage and disingage, until finally nothing. Jumping the plug that i put a picture of ingaged the compressor again. I drove it today and it worked fine and ac blew cold and engine idled up. The electric fan has to be connected to the ac somewhere so that soon as your ac is turned on the fan comes on no matter what your coolant temp is. Iím wondering by doing this i didnít screw something up. The fan is jumped at the ac fuse currently. Thanks for the help.
Thereís only one pressure switch in the system that reacts based on a pressure range. Itís around 29psi-429psi, from memory, donít quote me on that.
I canít tell what that harness plug goes to, I had mine out earlier this year but itís too far removed from my memory. You should be able to get a manual from an online source and check the schematics.
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Old 07-06-2018, 06:50 PM
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Originally Posted by mholme View Post


Thereís only one pressure switch in the system that reacts based on a pressure range. Itís around 29psi-429psi, from memory, donít quote me on that.
I canít tell what that harness plug goes to, I had mine out earlier this year but itís too far removed from my memory. You should be able to get a manual from an online source and check the schematics.
there are no empty exterior plugs left and the only other plug is inside the evaporator box for the pressure switch. So like you i have no clue what it goes to. Itís never been used since Iíve owned the pickup and everything worked fine.
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Old 07-06-2018, 07:09 PM
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Iím tempted to go out and drop my glovebox now that Iím curious what mine connects to, but in the mean time have a look here:

http://www.teamtoyota4x4.org/archivi...ci/aircond.pdf
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