300TD ac air recirculation

[smartin]

I've done a pretty good search on this subject

Right now there is no charge in the ac system. (I am refurbishing the components - both under hood and in dash board) Question: I have changed all the vacuum pods. The recirculation (large flap just behind glovebox) does not move - the old one had a leak - tested with mity vac. Does this flap function only when the ac is operable?
Note: The old one did work at one time.

Thanks Steve

[dmorrison]

The vacuum element for the recirc flap will only operate when the recirc button is pushed (note the car must be running to provide electrical control and vacuum to the AC system). That is the second button from the left. When this is pushed the control unit should send the signal ( vacuum) to the element to close the flap. So run the car and hit the recirc button. Check the operation of the element at that time. If it does NOT move then check the element, all the vacuum connections and hoses. If they are OK then it is your control unit in the dash.
If the car is all back together then drop the AC fan and check its operation looking thru the fan opening. You should see the flap move

Go here for information

http://skinnerbox.steaky.org/Service/W123/Index/Groups/83ClimateControlSystem.htm

Dave

[smartin]

The second button from the left (next to defrost) - the button does not say "recirc"? Does this mean if the ac has no freon the switch will work?

[psfred]

Use your MitiVac to test the servo as installed by connecting directly to the vac line. If it holds vac, but does not move the flap, either the flap is jammed or the linkage fell off.

Peter

[dmorrison]

Refer to the thumbnail below for the button numbers


1 Defrost. Full fan, full AC with compressor running, full heat. Air should come out of the windshield vents only.

2. AC controled by temp dial. Compressor on. fan speed and vent usage controlled by temp selected. fresh air flap CLOSED. you should hear the air rush volume decrease.

3 AC controled by temp dial. Compressor on. Fan speed and vent usage controlled by temp selector. fresh air flap OPEN. Flow and volume should increase from button 2 usage.

4. "EC" economy. AC compressor off. Fan speed and vent usage controlled by temp dial. Fresh air flap OPEN.

5 Off. Everything is off.

Blower switch.
Top button. Full fan speed, actually step (speed) 6. Temp dial will TRY to control temp

Middle "auto" button. Fan speed controlled by temp dial and limited to steps 2-5.

Bottom button. step 1 fan speed only.

Temp dial. Controls the vent usage and fan speed except in 2 positions.

1st, In "max" (coldest temp) the AC will give you all it's got, fan speed and compressor full cold.

2nd position were the temp control does not do anything is when BUTTON 1 is pressed, then the AC system gives you full heat, full AC and full fan speed ONLY out of the windshield vent.

When in button 2,3 and 4, IF the fan button is in auto the controler will vary vent usage and temp based on what you are requesting. Cold air and you get the 4 dash round vents used. Full heat and the air flows from the windshield, side round vents and the floor output. Any position in between and the AC controller decides. With broken components ( elements, vacuum lines, controller, mono valve), who knows what will happen.

Dave

[dmorrison]

Originally Posted by smartin

The second button from the left (next to defrost) - the button does not say "recirc"? Does this mean if the ac has no freon the switch will work?

With no freon all that will happen is the same as I described above but the evaporator will not be cooled by freon so the AC controller will continue to TRY and cool the car but the air will not be cooled. Everything else will work as described above. Just as when the car is first started and you want heat. Everything will work fine but the water going thru the mono valve is cold so no heat will be felt out of the vents and into the car.

Compressor usage is determined by the temp requested in the dial and the button pushed. Wether the compressor comes on is controlled by 2 things.

1 the pressure switch in the freon line at the reciever dryer must give the signal, or close the series circuit switch to allow the 12 volt signal from the AC system to get to the compressor clutch. No pressure, no 12 volts to the compressor clutch.

2 The AC controler must be requesting that the compressor turns on. Want heat, no compressor. Want cold air, compressor.

Dave

[smartin]

Mahalo Dave

1. There is no freon, nor receiver switch (receiver is out), so it looks like my test is not valid.

2. The only time the flap even tries to close is when the third button is pressed - the flap wil move about 1-1/2" then quickly move back. When the car is off, the flap is closed - recirculation mode.

Conclusion? System must be charged, compressor running, to have accurate test?

Am I getting closer?

Thanks Steve

[smartin]

After looking through 123 manual - all the tests for recirculation valve indicate "compressor on". For my tests - this is not possible - system has no freon charge. Looks like I will have to finish - charge system - then test.

Steve

[psfred]

The flaps should work correctly even if the compressor does not run, the "compressor on" note is just that, a note that the compressor will normally be running.

You can do the testing before recharging.

Peter

[smartin]

HELP

I really need to get the recirculation flap to go in recirc mode - which it does not do it now. The flap will move 1" then just as quickly move back to fresh air position. Would like to get recirc mode for the AC to be it coldest. Anyone??


Thanks Steve