07-29-2020, 04:34 AM
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#1
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AC clutch issue
I have a 99 with almost 220k. The manual AC system is acting up. The clutch only engages when the throttle is depressed. It no longer kicks in on its own. I can hear a relay clicking in the passenger side area.
Can anyone shed some light as to what I should look at?
Thanks,
Scott
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99 T4R SR5. OME 906s rear.Stock front springs with 1/4" spacers and Bilstein HDs all around. B&M trans cooler. Deck plate mod and rear diff breather mod. Blacked out bumpers and graphite wheels. Cobra CB in the ashtray. Tundra 199 brake upgrade. Pioneer MVH360BT head unit.
Necessity is the mother of invention.
Recent studies have shown that aggressive therapy combined with owning Toyotas, can be affective in breaking the cycle of Jeep addicition.
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07-29-2020, 08:15 AM
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#2
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I would take it to an shop with an AC machine to have it checked. If I had to guess, you probably have a small leak somewhere and you've lost refrigerant. The compressor will not engage if the refrigerant level becomes too low and you're probably right at that threshold.
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07-29-2020, 12:34 PM
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#3
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You might try swapping the A/C relay (I think the FI relay is the same) just to confirm the relay is ok.
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07-29-2020, 03:31 PM
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#4
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Quote:
Originally Posted by thegipper
I would take it to an shop with an AC machine to have it checked. If I had to guess, you probably have a small leak somewhere and you've lost refrigerant. The compressor will not engage if the refrigerant level becomes too low and you're probably right at that threshold.
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The refrigerant is full and blows cold.
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99 T4R SR5. OME 906s rear.Stock front springs with 1/4" spacers and Bilstein HDs all around. B&M trans cooler. Deck plate mod and rear diff breather mod. Blacked out bumpers and graphite wheels. Cobra CB in the ashtray. Tundra 199 brake upgrade. Pioneer MVH360BT head unit.
Necessity is the mother of invention.
Recent studies have shown that aggressive therapy combined with owning Toyotas, can be affective in breaking the cycle of Jeep addicition.
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07-29-2020, 03:32 PM
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#5
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Quote:
Originally Posted by azrex
You might try swapping the A/C relay (I think the FI relay is the same) just to confirm the relay is ok.
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The relays aren’t the same. The clutch relay looks like a small computer board that lives in front of the blower.
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99 T4R SR5. OME 906s rear.Stock front springs with 1/4" spacers and Bilstein HDs all around. B&M trans cooler. Deck plate mod and rear diff breather mod. Blacked out bumpers and graphite wheels. Cobra CB in the ashtray. Tundra 199 brake upgrade. Pioneer MVH360BT head unit.
Necessity is the mother of invention.
Recent studies have shown that aggressive therapy combined with owning Toyotas, can be affective in breaking the cycle of Jeep addicition.
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07-29-2020, 04:31 PM
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#6
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Do you have a 12v signal to the compressor when the system is turned on?
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07-29-2020, 04:35 PM
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#7
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I don't have the wiring manual for a 1999, but for a 2000 with manual AC, the wiring manual states the following:
"When the blower SW is set to on, current from the HEATER fuse flows through the A.C fuse to TERMINAL 1 of the A/C dual pressure SW to TERMINAL 2 to TERMINAL 1 of the A/C amplifier. The engine speed signal from engine control Module and the evaporator temp. signal from the A/C thermistor are all supplied to the A/C amplifier. When the A/C SW is turned on, the A/C SW on signal is sent to activate the A/C amplifier. Current flows from the A/C amplifier to the magnetic clutch, turning the compressor on. The A/C operation is shut off when a signal indicating low evaporator temp., or abnormally high or low refrigerant pressure, is supplied while the engine high speed signal exists. When one of these signals is received, the amplifier shuts off the A/C operation"
That would suggest that the A/C amplifier will shut off the AC clutch if engine RPM is too low. Since reving the engine makes the clutch engage I would start by looking at this area. How high do you need to get the RPM's before the clutch engages? It seems like either the A/C amplifier is getting a bad signal, or the A/C amplifier itself is going bad.
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07-30-2020, 12:56 AM
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#8
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Quote:
Originally Posted by Skulking
I don't have the wiring manual for a 1999, but for a 2000 with manual AC, the wiring manual states the following:
"When the blower SW is set to on, current from the HEATER fuse flows through the A.C fuse to TERMINAL 1 of the A/C dual pressure SW to TERMINAL 2 to TERMINAL 1 of the A/C amplifier. The engine speed signal from engine control Module and the evaporator temp. signal from the A/C thermistor are all supplied to the A/C amplifier. When the A/C SW is turned on, the A/C SW on signal is sent to activate the A/C amplifier. Current flows from the A/C amplifier to the magnetic clutch, turning the compressor on. The A/C operation is shut off when a signal indicating low evaporator temp., or abnormally high or low refrigerant pressure, is supplied while the engine high speed signal exists. When one of these signals is received, the amplifier shuts off the A/C operation"
That would suggest that the A/C amplifier will shut off the AC clutch if engine RPM is too low. Since reving the engine makes the clutch engage I would start by looking at this area. How high do you need to get the RPM's before the clutch engages? It seems like either the A/C amplifier is getting a bad signal, or the A/C amplifier itself is going bad.
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I have to just barely touch the throttle pedal to get the relay to engage.
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99 T4R SR5. OME 906s rear.Stock front springs with 1/4" spacers and Bilstein HDs all around. B&M trans cooler. Deck plate mod and rear diff breather mod. Blacked out bumpers and graphite wheels. Cobra CB in the ashtray. Tundra 199 brake upgrade. Pioneer MVH360BT head unit.
Necessity is the mother of invention.
Recent studies have shown that aggressive therapy combined with owning Toyotas, can be affective in breaking the cycle of Jeep addicition.
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07-30-2020, 10:50 AM
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#9
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Quote:
Originally Posted by T4Rscott
I have to just barely touch the throttle pedal to get the relay to engage.
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What is your idle rpm in both neutral and in drive once the engine is warm? Is there a consistent RPM threshold where the AC will engage and if so what is it?
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07-30-2020, 11:40 AM
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#10
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AC clutch issue
It’s interesting Toyota uses a control module with engine rpm to operate the AC.
Last edited by 19963.4lsr5; 07-30-2020 at 11:42 AM.
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07-30-2020, 03:32 PM
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#11
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Quote:
Originally Posted by LittleCaesar
Do you have a 12v signal to the compressor when the system is turned on?
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Not sure. I tried going from the battery to the connector using a lighted tester. The tester lit up, but did not activate the clutch.
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99 T4R SR5. OME 906s rear.Stock front springs with 1/4" spacers and Bilstein HDs all around. B&M trans cooler. Deck plate mod and rear diff breather mod. Blacked out bumpers and graphite wheels. Cobra CB in the ashtray. Tundra 199 brake upgrade. Pioneer MVH360BT head unit.
Necessity is the mother of invention.
Recent studies have shown that aggressive therapy combined with owning Toyotas, can be affective in breaking the cycle of Jeep addicition.
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07-30-2020, 03:35 PM
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#12
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Quote:
Originally Posted by Skulking
What is your idle rpm in both neutral and in drive once the engine is warm? Is there a consistent RPM threshold where the AC will engage and if so what is it?
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I only need to move the pedal about a half an inch. The idle is normal both in warm up and at normal temperature
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99 T4R SR5. OME 906s rear.Stock front springs with 1/4" spacers and Bilstein HDs all around. B&M trans cooler. Deck plate mod and rear diff breather mod. Blacked out bumpers and graphite wheels. Cobra CB in the ashtray. Tundra 199 brake upgrade. Pioneer MVH360BT head unit.
Necessity is the mother of invention.
Recent studies have shown that aggressive therapy combined with owning Toyotas, can be affective in breaking the cycle of Jeep addicition.
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07-30-2020, 05:23 PM
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#14
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Have you checked your alternator output at idle?
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07-30-2020, 08:15 PM
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#15
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Quote:
Originally Posted by T4Rscott
Not sure. I tried going from the battery to the connector using a lighted tester. The tester lit up, but did not activate the clutch.
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Then usually, but not always, it is safe to ASSUME that everything else is working and that the problem lies at the compressor. You can always take a DVM and see what values you get. Only once can I think of where I saw 12v at the connector for the compressor with the system engaged and the compressor wasn’t the problem.
I would then turn the system back on and if the compressor isn’t spinning, CAREFULLY lightly tap the face of the pulley to get it to try and activate. If it does start spinning, then look to replace the compressor.
Also, when increasing the RPMs, does the 4Runner have to be in drive or can it be in park?
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