RE: A/C Question
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RE: A/C Question - 7/2/2006 12:59:01 AM
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brodrick
Posts: 11
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I would say your best bet would be to get a vacuum tester and test the vacuum diaphragm first. (the one that pulls the throttle up when the AC kicks on). If that holds, you know it's coming from either the vacuum switch or the electrical signal that feeds it. I would replace the resistor assembly and see if the other problem doesn't go away.
Is it possible the compressor is staying on with the idle diaphragm disconnected because the idle is so low? It can't build enough pressure to kick out on high pressure unless the idle is kicked up by the vacuum actuator? Just a thought.
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RE: A/C Question - 7/2/2006 9:20:42 AM
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vette92
Posts: 21
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quote:
ORIGINAL: brodrick
I would say your best bet would be to get a vacuum tester and test the vacuum diaphragm first. (the one that pulls the throttle up when the AC kicks on). If that holds, you know it's coming from either the vacuum switch or the electrical signal that feeds it. I would replace the resistor assembly and see if the other problem doesn't go away.
Is it possible the compressor is staying on with the idle diaphragm disconnected because the idle is so low? It can't build enough pressure to kick out on high pressure unless the idle is kicked up by the vacuum actuator? Just a thought.
You were correct. I pulled the fan speed resistor and one of the coil resistors was burnt into. Just to see if that was the culprit, I twisted the wire coil resistor back together and A/C works, however it did not fix the abnormal idle going up and down, so now I will check the diaphram.
Thansk for your help, I really appreciate it.
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RE: A/C Question - 7/2/2006 10:23:16 AM
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brodrick
Posts: 11
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I'm just reading a little more about the "Idle up System" in my manual. Is your truck an Automatic or Manual Transmission? There is a dual speed idle control if you have an A/T vs only a single idle speed if you have a M/T with A/C.
It says to check the "servo Diaphragm", unplug it from the vacuum switch and plug it directly into manifold vacuum. That's easier than finding a vacuum tester. <duh on my part>. At that point, the idle should go up to 1300-1500 and stay there until you unplug the hose from manifold vacuum.
Then it says to to test the vacuum switch by removing the connector, and applying battery power directly to the switch (ground also) with jumper wires. The idle should go up and stay up for the duration of the direct power hooked up to it.
If that works, then you have to put a voltmeter on the wiring coming to the vacuum switch and turn the AC on to verify it's getting power to the switch at the proper time.
It's supposed to be on the B/R (black/red) of the idle solenoid connector the book says that when the A/C is on, you should have less than 1.5v, but when it's off, it should be 12v. While testing, the book recomends to leave the connectors hooked up, and pull the rubber cover off and put the tester down the backside of the connector along side the wire that goes into it. When the A/C is on, the voltage will drop as the circuit is made. If it fluctuates, you know where the problem is, but the book doesn't cover what to change if that signal isn't working...
Tom
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RE: A/C Question - 7/2/2006 8:54:59 PM
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vette92
Posts: 21
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quote:
ORIGINAL: brodrick
I'm just reading a little more about the "Idle up System" in my manual. Is your truck an Automatic or Manual Transmission? There is a dual speed idle control if you have an A/T vs only a single idle speed if you have a M/T with A/C.
It says to check the "servo Diaphragm", unplug it from the vacuum switch and plug it directly into manifold vacuum. That's easier than finding a vacuum tester. <duh on my part>. At that point, the idle should go up to 1300-1500 and stay there until you unplug the hose from manifold vacuum.
Then it says to to test the vacuum switch by removing the connector, and applying battery power directly to the switch (ground also) with jumper wires. The idle should go up and stay up for the duration of the direct power hooked up to it.
If that works, then you have to put a voltmeter on the wiring coming to the vacuum switch and turn the AC on to verify it's getting power to the switch at the proper time.
It's supposed to be on the B/R (black/red) of the idle solenoid connector the book says that when the A/C is on, you should have less than 1.5v, but when it's off, it should be 12v. While testing, the book recomends to leave the connectors hooked up, and pull the rubber cover off and put the tester down the backside of the connector along side the wire that goes into it. When the A/C is on, the voltage will drop as the circuit is made. If it fluctuates, you know where the problem is, but the book doesn't cover what to change if that signal isn't working...
Tom
It's a M/T. I have a vacuum tester so that was no big deal. The Servo Diaphram seams to be working fine. I can pull a vacuum on the diaphram with the tester with the truck running and it idles up just as it should and it is steady, depending upon how much vacuum I pull on the diaphram you can basically make it idle at any steady speed you want (more vacuum = faster idle).
I checked the voltage at the plug and here is what it says:
With A/C off both wires going to plug read 13.77 truck running.
With A/C on solid red wire jumps around to the idle speed of the engine, ie when it idles up the voltage is 1.7 when it idles down voltage shoots up to 13.7
With A/C on blk/red wire stays steady at 13.77
So what is the problem if it fluctuates?
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RE: A/C Question - 7/2/2006 10:16:03 PM
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brodrick
Posts: 11
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The only thing I have left is to try running a power wire directly to the solenoid valve to see if it works that way. If it does, then you know for sure the everything works except for the electrical signal that comes to the solenoid. Then you have to find where that comes from.
The book doesn't mention where the signal comes from so I don't know if it comes directly from the A/C Switch or from something else. My truck is Fuel Injected, so none of this is there for me to look at. I'm suspicious that it probably comes from the A/C relay. Everything else runs off that, ie the clutch and all the pressure switches etc. There is a B/R wire that comes directly off the A/C Relay and it could be the same B/R wire that goes to the idle up, but I'm just guessing.
Tom
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RE: A/C Question - 7/4/2006 1:04:30 AM
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brodrick
Posts: 11
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That's what the end result will be if it's hooked up.
You'll want to unhook the connector, and run 12v to the solenoid only.
The reason it shows the 12v and 1.5 volt results on a meter is hard to explain, but here goes.
It's probably got 12v coming to the plus side all the time, and then it connects the ground when it is activated to complete the circuit.
So, when it's off, the 12v is still there, but when it's on, the 12v is now connected through the solenoid to ground completing the circuit, so the voltage will drop as it is used for powering the solenoid.
That's why the book says "When it's off, you will read 12v, when it's on, you'll read 1.5 volt."
So, to run jumper wires, you disregard all that, and just run 12v to the plus side and hook the other side to ground.
Someone please correct me if I'm wrong, but this is the way I understand it.
Tom
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RE: A/C Question - 7/4/2006 10:48:38 PM
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vette92
Posts: 21
Joined: 6/3/2006
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quote:
ORIGINAL: brodrick
That's what the end result will be if it's hooked up.
You'll want to unhook the connector, and run 12v to the solenoid only.
The reason it shows the 12v and 1.5 volt results on a meter is hard to explain, but here goes.
It's probably got 12v coming to the plus side all the time, and then it connects the ground when it is activated to complete the circuit.
So, when it's off, the 12v is still there, but when it's on, the 12v is now connected through the solenoid to ground completing the circuit, so the voltage will drop as it is used for powering the solenoid.
That's why the book says "When it's off, you will read 12v, when it's on, you'll read 1.5 volt."
So, to run jumper wires, you disregard all that, and just run 12v to the plus side and hook the other side to ground.
Someone please correct me if I'm wrong, but this is the way I understand it.
Tom
Well, that makes pretty good sence to me, however, when it is off, both wires read the same 13.77 with truck running. So which one is ground? The one that goes down to 1.7 intermittenly?
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RE: A/C Question - 7/5/2006 10:30:45 AM
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brodrick
Posts: 11
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The book talks about the B/R (Black w/ red stripe) being where you check for 12v. I would venture that this would be considered the + wire.
It just says to check power between the B/R wire and ground and never mentions what voltage might be on the other wire. I would assume that the solenoid is working properly and that it's a wiring/controller/switch/ground issue that's causing it.
It sounds odd that one wire is fluctuating up and down like that. My guess is that this is where your idle fluctuation problem is coming from, but I don't know what on earth to check.
Tom
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RE: A/C Question - 7/8/2006 11:03:25 PM
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vette92
Posts: 21
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Thanks Tom for all your help. I'll track it down. At least now I have A/C.
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