MainePorsche

Guys,
I have alternator/battery voltage at one wire to the freeze switch (the one with two wires). The other wire has no voltage. Is this the way it is supposed to be ?
I have a new Greg Brown hvac controller that was just installed. Illumination and blower work fine.
Thanks in Advance.
Craig

Mrmerlin

do you have continuity through the switch?
The freeze switch is a part that should have continuity till it gets cold enough to open,
thus shutting off power to the compressor ,
this so the compressor doesnt keep pumping freon to the evaporator and causing it to ice up

MainePorsche

Stan,
I pulled the two wires off their spaded connections, and measured each. I've even jumped the wires and can't get my compressor clutch to engage.
It is more complicated. I'm now running through a secondary robust relay. Power and ground are good at the relay. I feel I can't check the 86 and therefore the 87 at the relay until this freeze connection thing is worked through.

Kevin in Atlanta

Wally's world: If the A/C compressor clutch does not engage, remove the plastic shield from the rear of the engine compartment, and find the antifreeze switch. With the ignition switch on and the A/C on max cool, test for 12 vdc on both of the switch terminals. If there is no power on either terminal, the most likely problem is the small relay in the control head. If there is power on only one terminal, the switch is either bad or misadjusted.

the flyin' scotsman

12v one side of the freeze switch should be seen on the other if not remove both wire and perform continuity on switch.

If theres 12v on both sides trace wire to compressor and recheck for 12 v, yes? if so the compressor may be hooped.

these an excellent Dwayne write up:

dr bob

Connect the freeze switch wires to the switch and test again. The readings you shared are to be expected with the wires disconnected. With them connected, you should see battery voltage on both terminals, reference to ground.

Mrmerlin

this test is done with the wires connected to the switch.^^^^

If you have power on both sides of the freeze switch then its closed and may open when it gets cold .

SO you may have low pressure in the lines, THUS
the pressure switch at the receiver drier needs to be jumped.
this should allow power to go to the compressor.

NOTE there are 2 switches at the receiver drier one turns on the fan,
the other is the low pressure switch

NOTE dont run the compressor more than 20 seconds with low freon as it could seize due to no oil being circulated

Kevin in Atlanta

Standard practice is to work from the compressor wire back to the control head.

Several folks have written up detailed instructions - notably Wally and Dwayne.

google search is your best friend with benefits.

a/c testing

MainePorsche

When I jump the freeze switch wires, I still get 0.0v at my 86 terminal of the new relay ?
I have muscled around my 14 pin connector in order to access my low pressure port - could this be a cause ? On second thought it probably is.

MainePorsche

I am attempting to fill COMPLETELY evacuated refrigerant. Should high pressure port be used when completely evacuated ? I was wondering about compressor engagement with no refrigerant.

MainePorsche

The manner by which it was evacuated of refrigerant was through the fuel cooler. I was told here, and by others locally, that the oil should still be for the most part still in the compressor. I was going to add 2 oz nonetheless. Would I be safe to jump the low pressure switch in order to fill with refrigerant through the low pressure port ? I am hooked up there and ready to go. BTW the freeze switch is relatively new (about two years old). All wiring for the new, secondary, relay very carefully done.

Mrmerlin

have you vacuumed down the system to test for leaks?

the low side fat line is normally used for filling this is done with the system running.
Once some freon is going into the low pressure line this should be enough to close the low pressure switch.
Thus turning on the compressor if the electrical lines are connected correctly.

Warning you could also fill via the small hose with the engine off.
HOWEVER with the engine /compressor running you would not want to be filling via the small line as it will explode the supply can

dr bob

[Thought]

The Greg Brown controller includes the up-rated AC compressor relay. There is no need for a second relay at the jump post or the compressor. Adding one just introduces another possible failure point, as well as a (typically) undocumented modification that will cause your ears to be unexplainably hot and red long after you've sold the car.

[/Thought]

MainePorsche

Thanks Stan.
So just to be sure, the two wires that need to be jumped to activate the low pressure switch in order to activate the compressor, are found at the BOTTOM of the stalk where the high pressure port sits above it ? There are two wires covered in rubber boots that sits atop this stalk, but I thought the low pressure switch was at the bottom. Please lead me down the right road amidst my confusion, and very long sentences.

MainePorsche

Thanks dr bob.
It probably is, though it looks about the same size as the original. I just thought to do the simple modification as I thought to DEFINITELY have the current load to the compressor clutch coming from a known robust relay and the small on the board relay handling the switching signal.