A/C wiring expert needed: replacement WOT A/C relay socket wiring question

[bcmbcmbcm]

Hey folks,

First of all many thanks for helping me diagnose a faulty WOT relay!

The bad news is that the black/yellow wire (which sends +12V to the compressor clutch) came completely out of the old ******* up relay socket, so I don't know where to solder in the new relay wire.

Right now I am looking at the old socket from the back where the wires go in. The 'clip' that holds the relay in the socket is on the bottom, and the 'bar' (forgive me for lack of better words) that ensures a one-way only insertion is to the upper left.

The wires that remain in the socket are all on the right side as I look at them from the back. The orange/green wire is to the upper right, the red wire is in the right middle, and the pink with ? stripe wire is on the right bottom.


Soooo.....I know the black/yellow wire must go to the left upper OR left lower position of this relay socket (it came out so I don't know which one!)....any experts out there want to chime in?

Thanks so much!

 

[HISSIN50]

As I recall, it should go to terminal 87A (the normally closed terminal). Said another way, it connects to terminal 30 when you're not at WOT.

You could use your DMM to check continuity between terminal 30 (common terminal - the power going into the relay from the LPCS) and the terminal you think it should be. Continuity should be present between 30 and the correct terminal when the relay is at rest (you're not at WOT).

Conversely, the wrong terminal should have no continuity to the inlet feed (terminal 30) if the coil is not energized (it only energizes at WOT).

I don't know if that helped or not but I figured the post couldn't hurt.

Good luck.

 

[bcmbcmbcm]

thanks...another question if you don't mind

As I recall, it should go to terminal 87A (the normally closed terminal). Said another way, it connects to terminal 30 when you're not at WOT.

You could use your DMM to check continuity between terminal 30 (common terminal - the power going into the relay from the LPCS) and the terminal you think it should be. Continuity should be present between 30 and the correct terminal when the relay is at rest (you're not at WOT).

Conversely, the wrong terminal should have no continuity to the inlet feed (terminal 30) if the coil is not energized (it only energizes at WOT).

I don't know if that helped or not but I figured the post couldn't hurt.

Good luck.

Can I make these checks with the ignition on and the engine not running (I already started tearing it down for a 306 swap)?

What does LPCS mean?

Is termanal 30 the wire that gets hot when I switch the A/C on on the dash?

 

[HISSIN50]

LPCS = Low pressure cycle switch. It's the electrical switch on the accumulator (passenger firewall) that lets the AC work in the first place (if pressure is low, the switch shuts opens).

Basically, power goes from the HVAC controls to the LPCS to the WOT relay and to the AC clutch.

For your testing, note which wire comes from the LPCS (pink/blue or something like that, IIRC from when I rewired mine. I didnt check your other thread but someone might have provided wiring diagrams on that thread). Make a mark on your relay to note the load side power input wire (this is the one that's hot only when you actually turn the HVAC knob to AC settings. The other hot terminal in the relay goes hot with the key turned on - you don't care about that last one).

Now remove the relay, go to your workbench and set your meter to 200 ohms scale. Place one lead on the terminal you just marked (that connected to the wire from the LPCS). Now touch the other probe to one of the other terminals in question. Now touch that second lead to the other terminal in question. One of these two tests will show a real low ohm reading and one will show an open circuit (often an I reading). Use the one with the real low ohm reading (which means there's not much resistance between the two terminals in the relay, which means they normally are connected). This low ohm reading terminal is the one you want.

Kinda make sense? It takes 30 seconds to show someone but is very hard for someone as inarticulate as me to try and explain.

Good luck.

 

[bcmbcmbcm]

http://forums.stangnet.com/showthread.php?t=684595

That is my previous thread with the diagram.

If I am reading this correctly,

The green purple wire gets hot from the HVAC controls and sends +12V to the low pressure cutoff switch (called on this diagram Cond. Press switch);

since my system is charged +12V will continue through this switch, on to the pink/lt blue wire to the WOT relay;

I need to check for continuity (per your instructions) between where this pink/lt blue wire enters the relay and the two terminals in question.

It sounds like you are saying the relay is normally 'closed'; meaning when the relay is in its 'natural, untripped state'; or unless there is a +12V signal from the coil wire indicating WOT, +12V should ALWAYS flow from the pink/lt blue wire to the proper terminal (where the black/yellow wire to the compressor clutch connects).

Yes this stuff is hard to articulate but does it sound like I get it ???

thanks again!

 

[HISSIN50]

I need to check for continuity (per your instructions) between where this pink/lt blue wire enters the relay and the two terminals in question.

It sounds like you are saying the relay is normally 'closed'; meaning when the relay is in its 'natural, untripped state'; or unless there is a +12V signal from the coil wire indicating WOT, +12V should ALWAYS flow from the pink/lt blue wire to the proper terminal (where the black/yellow wire to the compressor clutch connects).

Yes this stuff is hard to articulate but does it sound like I get it ???

thanks again!

I think you got it. The relay does not interrupt the power to the compressor unless the relay becomes energized, which occurs only at WOT. Otherwise, the relay passively allows power to go through it.

 

[bcmbcmbcm]

can't find my multimeter...used a test light

Can't find my multimeter when I need it

I used a test light and found what I think is the right one!


I checked it with the engine off but the ignition on...

Do you see any potential problems in doing it this way (either from the lack of a running engine or using the light?)

THanks!

 

[HISSIN50]

Can't find my multimeter when I need it

I used a test light and found what I think is the right one!


I checked it with the engine off but the ignition on...

Do you see any potential problems in doing it this way (either from the lack of a running engine or using the light?)

THanks!

Using a test light to find the terminal in the relay that is internally 'connected' to the pink/lt blue terminal should work fine.

Once things are back together with the car, test the relay to ensure that it opens the AC circuit at WOT. A quick blip of the throttle is enough.