Air Conditioning Dependencies (on a 3VZ-FE)

[tkNukem]

I've been trying to get my Camry back into shape by restoring the A/C system and fixing some problems like the center face vents not opening and some other minor issues.

But this A/C system has me most puzzled. The A/C light on the center console panel will come on, but nothing engages. During the first troubleshooting step, I traced it back to a faulty clutch/compressor. I put on a replacement, but the A/C still doesn't come on - yet the button will still illuminate. I know the compressor works and the air cools because when I force it to run (put 12V across the proper connector), the magnetic clutch engages and the compressor kicks on. I've tried a new magnetic clutch relay as per the dealer's suggestion, but it's still no-go.

I've been trying to test the system from the A/C Amplifier harness as per 1MZ's manual, and most of it looks good. However, I don't get any voltage from clutch relay or from the triple pressure switch - could that be part of the problem? Then again, would the relay and sensor be working when the compressor isn't running?

I just put another call into the service dept. and they mentioned that the compressor and A/C system, as a whole, would not operate without a working hydraulic cooling fan system/ECU. Maybe I missed that part of the 1MZ's troubleshooting guide - can anyone confirm that requirement on the 3VZ-FE? They recommended against jumping that portion of the A/C system because it helps regulate pressure...what do you guys think?

As it stands, I'm scrambling for a replacement cooling fan from salvage yards (hydraulic motor, shroud+fan, high pressure hose). The dealer quoted me $1,000 for a replacement setup.

Is anyone familiar with backward compatibility? Does the cooling fan system (hoses, shroud, ECU, motor) from a 1MZ work on a 3VZ? Out of curiousity, would a compressor from the 1MZ fit my 3VZ? I called pep boys a while back, and they said it's a different part number...I'd like to get another compressor just in case my dies from my troubleshooting steps

[davemac2]

Did you properly evacuate and recharge the system and measure the hi and lo side pressures? You sound proficient, but I don't know how well you know A/C. Is your hydraulic fan actually WORKING? You are not clear on that. Those hydraulic fans are pretty much impossible to find except at the dealer or a junk yard as you have indicated (if you can find a lexus or camry v6 in the junkyard). You could always rig up an electric fan instead as long as the alternator can handle the extra load. The reason the hydraulic fan is used is to reduce noise in the XLE and Lexus models.

There are a few reasons the compressor might not come on:

1. low A/C pressure sensed from the hi/lo pressure switch.

2. ECU is preventing A/C from operating due to too high an engine temp, whether that condition actually exists or not. This should be an input to the A/C amplifier from the ECU.

3. compressor clutch is gone or the gap is mis-adjusted and not allowing the clutch to engage. Or something such as the clutch relay or another relay or fuse in series in this circuit is gone.

4. the evaporator thermostat is gone/open and not allowing the A/C to come on.


If the system comes on but shuts down fairly quickly, then it is usually due to excessively high pressure caused by:

1. Too high a freon charge, or a blockage in the system from debris from a blown compressor or sealant.

2. The condenser or fan is faulty and is not doing its job to cool the liquid freon causing a high pressure.

dave mc

[tkNukem]

wooo, dave. Depends on what you mean by "properly evacuate" The lines were opened when the replacement compressor went on, so I assume all the freon was evacuated. The system was refilled with 30 oz or so of R134a. The only way I could get a decent pressure reading was when I forced the compressor to come on with the 12v. The junky gauge that came with the retrofit kit measured 40 psi on the low side.

As for the fan... it doesn't exist. The previous owner removed the fan completely and put on an electric fan that'll turn on with the ignition (therefore always running when the engine is running). Will the A/C system not work without a hydraulic motor in the hydr. line? Or was that dealer talking crap?

The engine temperature seems ok, based on the coolant temp. sensor (stays just below the half-way point when the engine is at operating temp).

I'd assume the magnetic clutch is fine because of how cool the air is when I force that sucker to run.

Do you have a handy method to test the pressure switch, high engine temp, or evaporator thermostat broke conditions? Better yet, can I somehow jump those sensors in order to see if the system will work?

[Toysrme]

what a dumb fucking previous owner. the electric fans don't come remotely close to the power of the hydraulic ones.

CONDITIONING OPERATION
THE A/C CONTROL ASSEMBLY RECEIVES VARIOUS SIGNALS, I.E., THE ENGINE RPM FROM THE IGNITER, OUTLET TEMPERATURE
SIGNAL FROM THE A/C AMBIENT TEMP. SENSOR, COOLANT TEMPERATURE FROM THE A/C THERMISTOR AND THE LOCK SIGNAL
FROM THE A/C COMPRESSOR, ETC.
WHEN THE ENGINE IS STARTED AND THE A/C SW (A/C CONTROL ASSEMBLY) IS ON, A SIGNAL IS INPUT TO THE ECU. (BUILT IN THE
A/C CONTROL ASSEMBLY).
AS A RESULT, THE GROUND CIRCUIT IN A/C CONTROL ASSEMBLY IS CLOSED AND CURRENT FLOWS FROM GAUGE FUSE TO
TERMINAL 1 OF A/C MAGNETIC CLUTCH RELAY " TERMINAL 2 " TERMINAL MGC OF A/C CONTROL ASSEMBLY " TERMINAL GND
" GROUND, TURNING THE A/C MAGNETIC RELAY ON, SO THAT THE MAGNETIC CLUTCH IS ON AND THE A/C COMPRESSOR
OPERATES.
AT THE SAME TIME, THE ENGINE CONTROL MODULE (ENGINE AND ELECTRONIC CONTROLLED TRANSMISSION). DETECTS THE
MAGNETIC CLUTCH IS ON AND THE A/C COMPRESSOR OPERATES.
OPEN DIRECTION TO AVOID LOWERING THE ENGINE RPM DURING A/C OPERATING.
IF THE A/C CONTROL ASSEMBLY DETECTS THE FOLLOWING CONDITIONS, IT STOPS THE AIR CONDITIONING:
* THE TEMPERATURE AT THE AIR VENTS IS LOW.
* THERE IS A MARKED DIFFERENCE BETWEEN THE COMPRESSOR SPEED AND THE ENGINE SPEED.
* THE REFRIGERANT PRESSURE IS ABNORMALLY HIGH OR ABNORMALLY LOW.
* THE ENGINE SPEED DECREASES.
* RAPID ACCELERATION OCCURS.

[tkNukem]

honestly, I can't blame him. Based on the ease of finding a replacement in different you-pull-it yards, it seems the hydraulic cooling fan setup was a common point of failure. what's worse is that the dealers cash in on such a poorly engineered system by pricing $1,000 for replacement parts alone.

By the way, that procedure looks familiar - is that from the '94 camry wiring manual? Would the 1MZ's A/C system be a close match to my 3VZ? I don't think I have an A/C control assembly...unless that's what they're calling the A/C amplifier. I used the 1MZ's a/c manual to test the amplifier connector, and most of it checked out besides that pressure sensor and the relay. Then again, the 1MZ's a/c manual also shows that the pressure switch takes input from the "cooling fan control". But that proc. you posted doesn't say that the 'a/c control assembly' relies on input from the pressure switch specifically to turn on. Ugh, mind == blown

And wow, this part must be a direct translation from Japanese, eh?:

AS A RESULT, THE GROUND CIRCUIT IN A/C CONTROL ASSEMBLY IS CLOSED AND CURRENT FLOWS FROM GAUGE FUSE TO
TERMINAL 1 OF A/C MAGNETIC CLUTCH RELAY " TERMINAL 2 " TERMINAL MGC OF A/C CONTROL ASSEMBLY " TERMINAL GND
" GROUND, TURNING THE A/C MAGNETIC RELAY ON, SO THAT THE MAGNETIC CLUTCH IS ON AND THE A/C COMPRESSOR
OPERATES.

[davemac2]

Well, I'm not sure if there is a BIG difference between the electric and hydraulic fans in terms of performance, so I would have to disagree with that statement above. As I said previously, the reason for the hydraulic was noise reduction. As long as you can match the air movement of the hydraulic with a suitably sized electric to move the same amount of air, you should be fine. What may suffer a bit is mileage since the fan is always on.

tkNukem, it does not sound like you removed the air from the system with a vacuum pump before rechargiing it. That needs to be done to remove all traces of moisture too. As well, I don't know what year this camry is or if it was ever converted to R134-A, but 1993 and prior years were all R12. 30oz is about right for R134-A anyways. I assume you jumpered the clutch to force it on when you charged it? Bring it to a shop to get properly evacuated, then you can always charge it up yourself again.

I don't see why not having a hydraulic fan will not allow the A/C to come on? As long as the condenser is getting cooled, the A/C hi side should be fine. The dealer may have stated this because possibly there is some sort of hydraulic pressure sensor fed to the A/C module/amplifier (same thing) that will not allow the clutch to engage if it is not high enough to run the fan.

Is this a camry or a lexus? what year? you can find some more factory manuals here: http://www.automotiveforums.com/vbul...d.php?t=497839

There are all kinds of diagnostic steps in those manuals to test the pressure switches, sensors, etc.

dave mc

[dc_98_cam]

Assuming that your AC system is similar to the 1MZ-FE, just ground pin 3 of connector 7, which is the ECM input for the 'oil pressure fan'. This will tell you if that particular component is the one which is preventing the clutch and compressor from energizing. ... Nothing complicated required here. ... Just run a ground wire from pin 3 to a clean metal chassis ground ... no paint, rust, or oil .... bare metal. .... Basically, this is all that the fan sensor does, anyway. .... You might have to look at the AC schematic to figure out which is connector 7. It is the same connector that connects to the triple pressure switch.

.... If you've jumped the clutch relay, and know that the system will cool, you've got the major problems solved already. ... It's just a matter of getting the one remaining link .... whatever it is, to work. .... Could be the thermistor, revolution detecting sensor, maybe something else. ... but just minor problems.

.... Using the following GEN 3 AC schematic for reference:
http://www.**********s.com/camry/ac.pdf

[Toysrme]

common part to fail? i've not seen more than a handful fail in person and none on the internet in YEARS.
and toyota used those in everything from the old LS 400's, sports cars, to a gabillion Camry's from 92-94. so it's not like they didn't use the hell out of it for awhile.
the hydraulic fan easily & obviously outpowers the single and dual electric fans that replaced it with the engine idling... when the powersteering pump is developing the least pressure. if you check the specs, there is another 142psi left for it to rise & accellerate the fan one the engine rpm's rise. (idling is 142psi... that's double the power avalible with the rpm rise!)





sorry i forget to post the link.
use the 1993 lexus ES 300 manual. that way you actually get the info on all of your components instead of the revised 1994 and 95 systems in the avalible camry manuals. which are awesome, and you need to have them, but the ES manual doesn't leave you guessing to what was going on the year before. (fewer differances in the ES manual VS your car than the 94 camry manual)
http://phatg20.net/modules.php?name=...ownload&cid=98


pay attention to the troubleshooting section of that 93 FSM. see if you can get it to trip codes, or find a faulty circuit manually.