A/C Compressor Problem (1 Viewer)

[NorCalDoug]

Not a huge problem...it's just not coming on.

I searched the archives, but couldn't find anything specific to what I'm experiencing.

I took the wife's 97 LX 450 to the A/C shop. They confirmed that there's plenty of refrigerant in the system. The A/C compressor is not coming on in Park, Neutral, Reverse, or Drive.

The guys at the shop seem to think that it's likely one of several relays -- they simply didn't have the right diagnostic tools to isolate which relay(s) might be a problem. I'm ready to apply a "shotgun" approach and simply replace all the relays associated with the AC compressor.


Anything I should try first?

Any reason I shouldn't swap out all the relays?

My alternative would be to take it to the dealership and have them diagnose and resolve the issue.

 

[cruiserdan]

Not a huge problem...it's just not coming on.

I searched the archives, but couldn't find anything specific to what I'm experiencing.

I took the wife's 97 LX 450 to the A/C shop. They confirmed that there's plenty of refrigerant in the system. The A/C compressor is not coming on in Park, Neutral, Reverse, or Drive.

The guys at the shop seem to think that it's likely one of several relays -- they simply didn't have the right diagnostic tools to isolate which relay(s) might be a problem. I'm ready to apply a "shotgun" approach and simply replace all the relays associated with the AC compressor.


Anything I should try first?

Any reason I shouldn't swap out all the relays?

My alternative would be to take it to the dealership and have them diagnose and resolve the issue.

When does it come on?

 

[NorCalDoug]

When does it come on?

It doesn't anymore...as far as I can tell.

Is there a way to force it on?

 

[97 FZJ80]

Doug,

You can test the system by bypassing each of the cutoff switchs for the compressor. IIRC, there are at least three, low pressure cutoff in the high pressure line, freeze cutoff by the evaporator, and a throttle/vacuum sensor. Any one of these switch malfunctioning would cause the compresssor to not come on.

John

 

[NorCalDoug]

Thanks John...I must admit, I'm a tard when it comes to bypassing switches...what's the best way to bypass?

 

[97 FZJ80]

Most of switchs on the AC system can be "bypassed" by shorting out the terminals (closed position). Since I do not have a electrical diagram at work, please confirm this before shorting anything!!!

 

[CJF]

1) Check fuses

2) Isn't there some sort of switch/connector by the dryer in FZJ's? I seem to recall someone having your problem and reporting back, "Oops, it was just that switch by the dryer."

Curtis

 

[NorCalDoug]

The fuse was the first thing that was checked -- good tip though.


I'll check the EWD and the FSM before messing with much.

 

[offroadkid]

Hey Doug, I did a quick search on alldatapro.com, and it looks like the Lexus A/C is controlled by an A/C automatic amplifier. I don't know exactly what to check, but I found this under description of operation. BTW, it's located behing the glovebox.

5. AIR CONDITIONING OPERATION
The A/C automatic amplifier 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, etc.
When the engine is started and the A/C SW is ON , a signal is input to the A/C automatic amplifier.
As a result, the ground circuit in the A/C automatic amplifier is closed.
At the same time, the engine control module detects the A/C magnetic clutch is ON and the A/C automatic amplifier operates.
Open direction to avoid lowering the engine RPM during A/C operating.
If the A/C automatic amplifier 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.

Under the troubleshooting section, the only two components listed for no A/C operation are the A/C fuse, and the System Amplifier. I still have it up in another window if you have any Q's! HTH!!!

 

[CJF]

Doug,

Here's the post I was thinking of. Turns out it was on a '91, but hey, might help?

https://forum.ih8mud.com/showpost.php?p=529700&postcount=20

Good luck,

Curtis

 

[reffug]

Just hope it wasn't the same problem I had......

Although it doesn't sound like it.

 

[alia176]

Doug,

if you're comfortable with a volt meter, you can test your way around the circuit. It's quite simple, really. I had a similar problem before heading out for the long road trip and it turned out that I forgot to plug in the connector at the Trinary press switch that's on top of the A/C drier. This is the reason why my compressor wasn't turning on.

You can turn on the car, activate the A/C system then look for 12vdc at key locations. If the voltage isn't present then you will at least have a starting point. Sometimes, it's just a simple connector that may have a bent pin inside. Pressure switches are key locations in an A/C system so check them using the continuity part of the meter. The EWD will help you find these locations. PM me if you want to chat over the phone and discuss the EWD.

Ali

 

[Koffer]

pull the pink pantys out of the auto climite control

what about pulling the dash and switching it to manual and see if that does it

 

[97 FZJ80]

On the auto-climate control, you can override the auto-AC function by selecting the AC function manually. The compressor will be on regardless of the other functions until you de-selects the AC or go back to auto-mode.

 

[NorCalDoug]

hmmmmm...

just learned from a pretty good source that if the A/C refridgerant level is low just a tad bit, the compressor will not kick on.

since the 80 tends to hold more R134a than other vehicles, perhaps my slack-jawed A/C tech was mistaken...maybe I do need just a bit more R134 in the wife's rig?

 

[Tentsontop]

I hope you find the problem. I still haven't gotten my AC sorted out. Mine works for a few minutes then blows warm, the high/low side temps equal out just after that. The compressor seams to be working the whole time. If I turn it (ignition) on and off a couple times it will work for twenty minutes or more. I've got my manifold guages now. Hope to have some answers soon.

 

[alia176]

Your A/C pressure is indicated by the press sw that's located on top of the drier. Refer to the manual to see what state it needs to be in so that the system will operate. Either the contacts are closed/shorted when system is full or the opposite (open circuit). A simple continuity test will back this up.

Ali

 

[RavenTai]

The AC clutch system in the LX450 is pretty much the same as in the LC, most of the Auto AC differences are in the cab,

First place I would check is the pressure switch, unlike most vehicles it is not only opens (no continuity) with too low of a pressure but also with too high of a pressure.

pull the connector off the switch (just in front of the battery mounted on a AC line) and short the two pin on the harness side together, if the compressor starts to turn then the switch is not happy with the pressure. Either too high or too low, or the switch is bad.

Do not run the compressor long without proper pressure or you will kill the compressor.

All of these parts are in series, current goes from one to the next, each parts gets a chance to veto AC compressor operation.

10A gauge fuse ->
A/C dual pressure switch, normally closed->
Starter cut relay, Normally Closed, power to coil by start signal through park/neutral switch opens contacts to turn off compressor during start->
Compressor relay, Normally Open, ground coil by AC amp closed contacts to turn on compressor->
Engine coolant temp cut relay, Normally Closed, coil grounded by AC temp cut switch opens contacts, if engine coolant above 226F, prevent compressor operation during overheat->
magnetic compressor clutch, engages drive belt to compressor->
Ground

The three relays look to be in the passenger side of the dash near the glove box near each other.

 

[Cube Dweller]

Doug, I think mine is working intermittantly too. It started acting funny after I did a coolant flush...one of the areas I started digging into was the coolant temp sensor, one of three installed in the side of the block. I just installed the aftermarket temp gauge so I can troubleshoot on the fly if the compressor kicks out when engine is in normal operating temp. Will let you know what I find.

 

[NorCalDoug]

Does anyone know how different, if at all, the LX 450 AC system is compared to a 1997 40th Anniversary or Collector's Edition model Land Cruisers?

My guess would be that they'd be the same, but I'm being told otherwise by the Toyota dealership.



They've had the wife's LX 450 for over 3 days now and THINK they've isolated the issue...they toyota techs seem to be baffled by the wiring behind the dash of a LX 450...apparently there's TONS more wires which in turn leads to a MUCH more complex system...


more details to follow...