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Not another typical AC problem

18K views 29 replies 5 participants last post by  Slick Nick 
#1 ·
So after reading many of the ac problem threads I still have unanswered questions. My AC light turns on and off. The heater fuse is fine. The compressor works fine and blows nice and cold air...however a few weeks ago I noticed that when I turned the AC off and then on it wouldn't always turn back on. I wasn't sure what the issue was but the next time I turned it on and it turned on I just left it on. So yesterday I switched to defrost and boom it no longer works. There is no power getting to the compressor when turning the ac button on or off. There is a faint clicking sound similar to an actuator or solenoid coming from behind/under the glove box when I turn the ac button on or off. I assume it is a relay or solenoid of some type but I don't know the layout of the ac system. Has anyone had this issue or successfully fixed this before? Anyone know the layout of the ac system how what exact part I need to replace?

Thanks,
Nick
 
#2 ·
Here (attached) is the 1999 HVAC wiring diagram.

It could be as simple as a blown 10A AC fuse.

I'm not clear what is and is not working. Does the blower (fan) still work, or is it dead? If the blower's dead, check the 40A Heater fuse.

The heater relay is in the engine bay fuse box, so that's not what you hear clicking beneath the dash.

The A/C amplifier (the controller unit) is located within the HVAC box beneath / behind the dash, but I don't know what should or should not be clicking in that area.
 

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#3 ·
The fan still works just fine. Is the a/c controller unit replaceable or can parts be changed within it? I've never torn that stuff apart so I am completely unfamiliar with the HVAC box and it's contents. When I attempt to switch to defroster or turn the ac button on all I get is a click behind the glove box. I checked the compressor and it isn't getting a power signal when the ac is switched on so the issue is somewhere between the ac button and the compressor.
 
#4 ·
I've never seen any FSM documentation about the 'innards' of the A/C amplifier (controller), so I guess it's a single swappable unit.
 
#5 ·
So I was looking at the diagrams from a online toyota parts catalog of the HVAC system and the only parts that I could find that could be making a clicking sound behind the dash are an expansion valve and a pressure switch. Could these be the culprit? I have no idea how all of these parts work in unison.

http://www.toyotapartsdirect.com/catalogs.html
 
#8 · (Edited)
so i just turned on the truck, turned on the fan and ac switch and gave the hvac box a good slap and the ac turned back on. Any ideas?
Attached are a couple pics of the amplifier. That's a relay on the board and is probably what you heard clicking. It is easily removed by unplugging the connector , removing the lower plastic cover by disengaging the locks, then sliding the board down and out. Since your a/c started working after smacking the housing this sits in, it may either be a loose connection at the connector or the amplifier itself may be going bad. I've never seen a "burned" board when looking at ones I've replaced in the past so looking at it probably won't do you any good. Try messing with the connector next time your A/C acts up
 

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#7 ·
Sounds like a sketchy electrical / wiring connection or maybe a heater relay going bad. The A/C switch itself might be the problem. :shrug:
 
#10 ·
Well I have done some reading around and it turns out that the expansion valve is a commonly worn part and is recommended to be changed at normal service intervals such as when the system needs to be recharged. It is only about $30-$40 so not very expensive. Since my truck has almost 300k miles and is 15 years old I figured some maintenance is in order. I ordered a new expansion valve, a pressure switch and a new motor and fan. Has anyone ever replaced an expansion valve before? Any advice?
 
#11 ·
#12 ·
Here (attached) are the removal procedures for the expansion valve and the evaporator (which apparently has to be removed to get to the expansion valve).
 

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#14 ·
I hope some here can help me or lead in the right direction... I have a 2005 Tacoma. when I press the recirculation button on there is I loud ticking noise coming from behind the glove box. I removed the glove box and see that there is a white plastic arm that is hung up causing the noise. once I press the recirculation button off the arm moves and the ticking goes away. ive done some research and read that its the blend door motor or air mix servo.... how do I remove this part and replace it or can I remove it and repair it???
 
#15 ·
I'm having trouble identifying this 'white arm' piece. Can you post a pic of it, or at least show where on the A/C / heat unit it's located?
 
#17 ·
Thanks for the pics. They help me figure out that the 'white arm' is connecting with the air inlet servo motor (the black box the wires attach to). However, I still can't find any FSM or other documentation that goes so far as to mention - much less illustrate / discuss - the mechanical linkage this servo connects to.

I notice dirt or dust built up on the white parts. You might try cleaning (if you can reach in there ...) to see if it's as simple as crud jamming the mechanism.
 
#24 ·
Have you checked whether the heater is working? If the heater relay was bad, it should prevent both the heat and the A/C from working.

If the A/C thermistor signals an abnormally low evaporator temperature it is supposed to cut off the A/C. I supposed a bad thermistor might cause the system to not power up, but I'm not sure.

I can find online parts vendors offering the A/C amplifier, but I assume it's a Toyota-specific part. None of the listings I found specified whether it was Toyota-built or sourced from somewhere else.
 
#25 ·
The heater seems to work fine. I will check the a/c amplifier to see if it is getting power and whether it is sending a signal out. Should be pretty straight forward.

http://www.toyotapartszone.com/oem/toyota~amplifier~assy~cooler~stabilizer~88650-04010.html

Toyota Part Number: 88650-04010


did a quick internet search and only found OEM
Thanks. Those are the same ones I found. The dealer wants about $95. Online oem parts dealers want about $80 including shipping and tax. There is a local Japanese Auto dismantler in Long Beach so Friday I will see if they have any and what warranty they offer. They have tons of stuff for Tacomas but their prices are usually on the high end.
 
#26 ·
FWIW ...

ToyotaPartsZone has that part number listed for $61.94.
 
#27 ·
So, I checked the a/c amplifier with my multimeter and there didn't appear to be power going out from it. The clicking that I heard when this began is coming from the amplifier. So I then thought the amplifier relay might have gone bad. The truck was running and the a/c was on at the time. I then grabbed the amplifier and all of a sudden the ac compressor turned on and the ac started working. It turns out that there is a wire issue. I believe the wires attached to the plug going into the a/c amplifier are not seated properly and when I wiggle them around the a/c turns on and off. So I found the culprit and now I need to figure out how to fix it...
 
#30 ·
like I had suggested two months ago Haha! .. ;) Well..I hope it's something as easy as tightening up tension on the connectors :waytogo:
Yeah, I know. It's been difficult to get time to work on it. At least the stuff that I replaced was cheap and good maintenance items. It cost me something like $50 for the expansion valve, the pressure sensor and the 2 cans of R134a. I also was able to clean out the cooler which looked like a rats nest and the blower motor. So it wasn't a complete waste of time. Also I lost my multimeter for like two months so that's another reason I wasn't able to check the electrical. Thanks though you two for the diagrams and help.
 
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