91 Camy Vacuum leak(?) &Other Problem

[lionheart03]

Here is my best description of the problem. When you have the AC on in the summer for example, the vents will only blow out warm air, until you hit gas, then it blows cold air like normal. Almost like a damper or vent somewhere is not closing/opening correctly. It does the same thing on heat, when at idle, cooler air is blown in until even the gas is slightly increased, then it blows warm air like normal.

I also noticed when I have the windshield defrost selected, while a good amount of air does blow out of the correct vent, air also blows from the dash and floor vents, like something isn't sealing to divert the air into the correct place. It does this on all vent settings. I've been told this could be contributed to a vacuum leak, as the problem seems to fix itself when the cars throttle is increased. Any ideas?

As for problem # 2. After my recent motor rebuild, the "Lights" light stays on. Checked all rear lamps as per the manual, and they are all lighting like normal. Anything else that could cause this?

Thanks in advancd for any and all help!
Jeremy

[Doctor J]

For a/c issue verify that the compressor runs during the rev-up of engine at park; the a/c cut amplifier suppose to disengage clutch when car is moving and accelerating [between 0 and 10 mph], moisture in the system can cause brief freeze up and momentary loss of cooling.
the direction which way air is blowing is not controlled by engine vacuum but by mode selector cble [black jacket, it connects control lever to the selector on the heater unit visible when knee pad is removed under steering column; make sure it is connected
#2 is most likely rear lights sensor, provided 3 stop lights are working

[typesix]

For the AC problem, there is an electrically actuated vacuum switch on the passenger side firewall in the engine bay. When AC is activated, the switch will create a small vacuum leak and cause the engine rpm to increase, the AC computer will sense this increase from rpm sensor on compressor clutch and allow the compressor to activate. This is to prevent possible stalling at low idle rpms. That's likely why you don't have cold air at low engine speeds. Rpm increases up to about 900 rpm at idle(neutral/park) when the switch is working properly.

[Doctor J]

To typesix:
When the a/c idle up solenoid valve opens, it allows the intake manifold vacuum to act on the diaphragm that opens the bypass around the throttle valve.[On older domestic carbureted cars it is done by throttle kicker] The later causes increase in engine speed; when solenoid de-energizes it connects the diapragm to the athmosphere which bleeds the vacuum off; the diapragm returns and that closes bypass.
The "vacuum leak" or bleed is used in EGR vacuum modulator

[fredk]

there is a little black box on the heater box behind the glove box with a tiny knob on it, its called an ac amplifier, the knob sets the low RPM cut out for the compressor, be sure the outer hub is turning at idle and fans are running, follow the cables down from the temp control head to the door they work at the other ends and be sure they are hooked up and working the doors

[lionheart03]

Thanks for all of the suggestions. It's been so freaking cold out here that I probably won't mess with my car for a few weeks. I did however turn the ac and observe the idle. The car idle did not increase when the compressor kicked on. I checked the vacuum switch for this, hoses were good and it was getting vacuum. When I unplugged the switch and plugged it back in, then the engine idle increased for a few second and went back down. Faulty switch? Might be a corroded connection also.

Last summer my car died a few times while coasting down with the AC on. I think this may be the problem.

Once again, thats for all of the help so far! I'll post a reply on here if and when I ever get this fixed.

[Doctor J]

the solenoid itself can be defective I replaced more then 10 in last 2 years