1990 A/C amplifier
 

Anyone know what the "AC Amplifier" does on a 90 camry DX? Apparently mine is intermittent so the AC guy is gonna bypass it for now. He stated that it was a small circuit board sitting underneath the AC evaporator in the dash of the car. He also stated that with the amplifier bypassed, the ac is working like a champ. I have had the entire AC system replaced with the exception of this one part because the entire system was bunk. I'm about $700 into AC system parts/labor and hoping this little board is not really necessary... haha.

The wiring diagram has an AC Cut Amplifier and an AC Amplifier (circuit board).

I am not sure I would operate the AC without either. The AC Cut Amp is tied into the AC compressor RPM sensor.

The AC Amp is tied into the temp sensor, idle up VSV (causes the engine to increase idle speed when the compressor is running), magnetic relay clutch for compressor and some other items.

If your mechanic is talking about the AC amp circuit board I think your asking for trouble in bypassing it. Not sure about the AC Cut Amp.

How is the mechanic bypassing the amp? Is the person jumping the magnetic clutch on the compressor?

Keep in mind the AC system has some safe guards such as over and under pressure switches, a RPM sensor that tells if the compressor is running OK and has not froze up. If the compressor is dragging due to possible failure or has froze up the AC system will turn off the magnetic clutch. If the compressor is hot wired the drive belt may fail due to the now frozen compressor and still activated magnetic clutch.

You can't find a used item?

Hey Toyo,

Thanks so much for the response. I was sure not to turn the AC on today after I picked the car up, beyond the 1st five minutes of driving to confirm clutch operation and cooling was as expected. Surprisingly, this car cools better than our 05 Titan and 08 Eclipse. I digress.

I was looking at the schematics this evening and from what I found, the tech jumped the connection on the AC amp where the violet/white wire connects. I suspect it is as you mentioned and he jumped the magnetic compressor clutch. It was dark before I could trace his jumper so I'm not sure, but I did see what I believe is an extra wire that now connects to the compressor/clutch. Further analysis over the weekend will confirm. I also discovered that this part is apparently not manufactured any longer but there are several pick'n'pull part locations in the DFW area with several dozen gen 2 Camry's. I plan to make a trip on Tuesday.When I took it back in, only 2 days after the AC system was replaced, the clutch was fried, the VSV seemed to test ok, pretty simple to test really, there was a relay that was questionable so I replaced it, and this relay, I believe, is tied to the AC amp. Really, with the information you provided, I believe the issue will be resolved once I replace the AC amplifier. I'm gonna grab an AC cut amp as well, just for safe measure, test them both and install. Once I locate the compression revolution sensor (I believe this car has one, haha:) I'm gonna get one of those too. At that point, I do not believe there will be an original component left on this AC system.

We are hoping to get at least 3-5 good years out of this car so from that perspective, the money will be well spent.

I really appreciate your response to this thread and a couple others I've posted. I've learned a lot and feel more confident working on this car myself. I have not owned an "old" car that demands regular TLC in over a decade but feel the "wrenching-juices" begining to flow again. LOL

I'll let ya know how this turns out. :)

Great!

So My catalytic converter has not shown up and I need to replace it in order to pass emissions. While I was sitting here today waiting for it to arrive, I played with the AC system some more in the hopes I can resolve that issue once I can legally drive to pick'n'pull parts to get replace the AC amp... frustrating to say the least considering the AC runs like a champ except the clutch burnt up two days after the compressor/clutch/etc was replaced

Here is what I discovered today

The VSV does not pass the manual vacuum test and with the car running and AC on or off, removing and attaching the vaccum lines creates no change in the car's idle, connecting and disconnecting the electrical connector makes no difference either. I confirmed +12 volts on the yellow/red wire when the AC is on

The wire that the mechanic jumpered on the AC amp is the Violet/White wire at pin 1 of the AC Amp. As best I can tell, the jumper wire connects to the compressor. It runs into a small black plastic case just between the compressor and the compressor pulley, and there is a black wire that comes out of that same casing that screws to the top of the compressor. The violet/white wire runs to the AC switch so I'm not too sure what it actually controls.

Tested the AC Amp connector today per the manual and found the following out of spec:

Battery voltage was 12.69v

voltage measure was low between:

pins 1 and 10 @ 11.54v
pins 2 and 10 @ 11.53V
pins 4 and 10 @ 9.83v
pins 5 and 10 @ 10.85v
pins 6 and 10 @ 11.53v

Simply blows my mind but I'm hoping by replacing the AC amp, AC cut Amp, and VSV valve, and UN-jumpering the Violet/White wire, the problem will be completely resolved before I throw myself into the freeway... haha

The guy told me that if I unjumped the wire without installing a good AC amp that I would burn the clutch up again but the AC would have no problem at all as long as I left the jumper on there.

Woohoo! converter just arrived this minute, gonna replace it once it cools off later this evening and hopefully pass inspection!

Appreciate anyone that reads/responds to this thread, not sure how I will know if the AC amp I install is good or not until the AC clutch does not burn up again... LOL

Send a private message with email address.

Will respond with info on AC system and a wiring diagram. Together these should help you.