1990 Camry a/c amplifier - Toyota Nation Forum : Toyota Car and Truck Forums

rd985 · 09-08-2011, 10:15 PM

I have a 1990 camry 2.0 automatic. The a/c intermittently cuts off during idle.

Searching through these forums leads me to believe that I may need to adjust the low idle cutoff with a screw on the a/c amplifier. I removed the glovebox, but I'm not sure where the amplifier is located. I see a "cigarette sized" box (DENSO 077100-2400). Is this the amplifier? If so, I don't see any type of adjustment screw.

Does anyone know where I can find a photo of the a/c amplifier and this screw that provides the low idle cutoff adjustment?

Thanks in advance.

71Corolla · 09-08-2011, 11:15 PM

I have two A/C amplifiers in front of me, neither of them have any type of adjustment. There is an A/C cut amplifier, maybe that has the adjustment? The horizontal one is the main unit (at the bottom) the other one is the cut amplifier. I think, going from memory here.

The part numbers for the modules I have are
077100-2242
077100-3511

edit - does the engine idle very low when the A/C is on?

rd985 · 09-08-2011, 11:51 PM

Thanks for replying. Yes, the idle does drop when the a/c is turned on. I thought it might be the idle-up solenoid. When the a/c is turned on, I can blow air through the solenoid (with a little resistance). When a/c is off, I cannot. I tried bypassing the solenoid anyway, but it's the same behavior: sometimes the a/c will run at idle, but sometimes it cycles off. If I raise the idle slightly by pressing the accelerator, it cycles back on.

According to the diagrams I've seen, the a/c cut amplifier is somewhere in the dash. From what I've read, it should have a knob to adjust the low idle cutoff. I can't seem to find a photo of it, though.

white90dx · 09-09-2011, 11:00 AM

Quote:

Originally Posted by rd985

Thanks for replying. Yes, the idle does drop when the a/c is turned on. I thought it might be the idle-up solenoid. When the a/c is turned on, I can blow air through the solenoid (with a little resistance). When a/c is off, I cannot. I tried bypassing the solenoid anyway, but it's the same behavior: sometimes the a/c will run at idle, but sometimes it cycles off. If I raise the idle slightly by pressing the accelerator, it cycles back on.

According to the diagrams I've seen, the a/c cut amplifier is somewhere in the dash. From what I've read, it should have a knob to adjust the low idle cutoff. I can't seem to find a photo of it, though.

There is no adjustment on the A/C amplifier or A/C cut amplifier. You need to adjust the A/C idle-up valve that is attached to the manifold (it is actuated by the A/C idle-up solenoid). There is a large screw with a spring behind it that does the job, it should be very easy to adjust. Adjust it up enough so that the idle while the compressor is engaged at the car is in gear (if an auto) raises slightly. If you have a manual trans, just have it bump up to maybe 900-1000rpm in neutral idling.

-Charlie

rd985 · 09-09-2011, 01:45 PM

Quote:

Originally Posted by white90dx

There is no adjustment on the A/C amplifier or A/C cut amplifier. You need to adjust the A/C idle-up valve that is attached to the manifold (it is actuated by the A/C idle-up solenoid). There is a large screw with a spring behind it that does the job, it should be very easy to adjust. Adjust it up enough so that the idle while the compressor is engaged at the car is in gear (if an auto) raises slightly. If you have a manual trans, just have it bump up to maybe 900-1000rpm in neutral idling.

-Charlie

I tried to adjust the idle using the large screw, but it didn't increase the idle and the clutch wouldn't engage. After bypassing the solenoid and adjusting the large screw, I was able to increase the idle enough to engage the clutch. It seemed to have a "sweet spot": backing the screw out increased the idle, but after a certain point the idle dropped back down.

With the screw adjusted in this sweet spot and the solenoid bypassed, the a/c seemed to run correctly. I let it run for about 10 minutes, and the a/c didn't cycle off. I took the car for a test drive, got to the stop sign at the end of the block and the a/c clutch was disengaging at idle again.

Back at the house, I popped the hood and rev'd the engine. The a/c engaged as the RPM's increased, but disengaged at idle.

I tightened the big adjustment screw all the way in and slowly backed it out. Once it hit the "sweet spot", the idle increased and the clutch stayed engaged.

I tried another test drive, but the result was the same: at the first stop sign, clutch was not engaging a idle.

white90dx · 09-12-2011, 10:59 AM

That's very odd about the adjustment screw... I never had any problems adjusting the idle up and down (A/C on, of course) with that screw. Check for loose/cracked vacuum hoses when you are under the hood next time.

Otherwise, how well is the A/C cooling? You may want to have a professional check system pressures. It could also be turning off due to low (or high) system pressure that only happens at idle. Based on my experience, the A/C doesn't turn off due to low RPM (I've had a bad A/C idle-up solenoid before and it idles at around 350-400 with the A/C on).

-Charlie

rd985 · 09-12-2011, 05:10 PM

Quote:

Originally Posted by white90dx

That's very odd about the adjustment screw... I never had any problems adjusting the idle up and down (A/C on, of course) with that screw. Check for loose/cracked vacuum hoses when you are under the hood next time.

Otherwise, how well is the A/C cooling? You may want to have a professional check system pressures. It could also be turning off due to low (or high) system pressure that only happens at idle. Based on my experience, the A/C doesn't turn off due to low RPM (I've had a bad A/C idle-up solenoid before and it idles at around 350-400 with the A/C on).

-Charlie

While checking for damaged vacuum lines, I discovered 2 vacuum lines disconnected. It seems that the plastic part(switch?) to which they were attached is broken. This plastic part screws into an extension of the intake that's located forward of the distributor cap.

Here's a photo:

Could someone help me identify this part?

Grego 92 · 09-12-2011, 07:43 PM

Check this link, it tells you all about it. It's a BVSV.

Whats this? Its on top of the thermostat housing

Doctor J · 09-13-2011, 01:31 PM

The broken part is used to allow purging of the charcoal canister (to suck the fuel vapors to the engine and to burnt hem when engine is above 135 degress F)
Get the vacuum pump and check the A/c idle up diaphragm, it may be leaking.
If a/c is not running at idle only, check the amount of refrigerant in the system (too low)

rd985 · 09-14-2011, 06:18 PM

I made a trip to a pick-n-pull and grabbed an idle-up solenoid, diaphragm, and BVSV.

After replacing these parts, it seems that the a/c is running correctly.

I just want to say thanks to 71Corolla, white90dx, Doctor J, and Grego 92. I really appreciate your help!

rd985 · 09-22-2011, 10:39 AM

I think I may have spoken too soon.

The problem with the a/c clutch disengaging at idle has returned.

The only difference is that now I get flashing light on the a/c button and the clutch will not re-engage until I use the button to first turn off the a/c and use the button to turn it back on. Before replacing the solenoid and the diaphragm, the a/c clutch would intermittently disengage at idle, but would re-engage whenever RPM's were increased above idle.

I put the gauges on the a/c system (with system on recirculate and blower on high) and they're reading 35-40 psi on the low side and 200-225 psi on the high side.

Are these readings within the normal range?

Doctor J · 09-22-2011, 11:27 AM

With the outside temperature at 90 F and engine at 2000 rpm (blower at high) the readings for R12 is about 30 for low side and 215 for the high side. So it is about right for R12; if the sight glass on the dryer is almost clear (w/ R12) system is properly charged.
are the fans also switched off when a/c is off?
You may want to hook up a test light or voltmeter to the a/c clutch positive wire and check if voltage is still present on it for 2 seconds after the inner hub stops turnig. If so, the compressor may have mechanical problem or system is restricted or the clutch coil has intermittent openings.
On my car when I disconnecting the coil and push a/c switch in, the cooling fans are starting to rotate, then a/c light flashes, and fans are coasting to the stop.

rd985 · 09-22-2011, 11:51 AM

Quote:

Originally Posted by Doctor J

With the outside temperature at 90 F and engine at 2000 rpm (blower at high) the readings for R12 is about 30 for low side and 215 for the high side. So it is about right for R12; if the sight glass on the dryer is almost clear (w/ R12) system is properly charged.
are the fans also switched off when a/c is off?
You may want to hook up a test light or voltmeter to the a/c clutch positive wire and check if voltage is still present on it for 2 seconds after the inner hub stops turning. If so, the compressor may have mechanical problem or system is restricted or the clutch coil has intermittent openings.
On my car when I disconnecting the coil and push a/c switch in, the cooling fans are starting to rotate, then a/c light flashes, and fans are coasting to the stop.

Before I got the car, the system had previously been converted to 134a. What should the readings be for 134a?

The fans do switch off whenever the a/c clutch disengages.

white90dx · 09-22-2011, 11:56 AM

Doctor J is probably on to something with the A/C clutch... that was the symptoms I had when my A/C clutch was going. Sadly, its a pretty expensive fix. Let us know what you find based on Dr. J's suggestions.

-Charlie

rd985 · 09-25-2011, 08:29 PM

Could someone provide the correct gauge readings for 134a? Should they be in the same range as the readings for R12?