a/c conversion questions

[pnhigg]

I have a 92 fullsize with a 5.3/T56.
I have retrofitted the original a/c system to r134a, and made brackets to use the original-style compressor.
Currently I have nothing connected to the pcm and the a/c is controlled through the in cab thermostatic controls in the dash (I am sure they are called something else).
I have two wire running from the clutch cycling switch on the accumulator both 12 volts. One runs to the compressor clutch, and the other is loose, but was connected to the original pcm that the truck had when it was a 4.3.

Where (what pin) on the new pcm do I need to supply 12v, so the engine rpm will increase when the a/c clutch is engaged?
Also what pin do I need to connect to to signal the electic fan to come on when the a/c compressor is engaged?

Hope this makes sense, thanks for the help.

[r6z4o6]

According to my 1991 GM C/K Pickup Electrical Diagrams,

When the ignition Switch is in RUN, battery voltage is applied through the A/C-HTR Fuse(brown wire) to the coil and contacts of the AC Clutch Relay.

With A/C ON selected, Terminal 966(Dk Blue/White) of the Heater and A/C Controller is grounded which energizes the A/C Clutch Relay.

The contacts of the Relay close and battery voltage is applied(Lt Green) through the closed contacts and the normally closed A/C Accumulator Switch to the coil of the A/C Compressor Clutch(via Dk Green wire).

>>There is a junction here. The Dark Green wire *also* goes to PIN B8 [Circuit 59] in the '91 ECM labeled Air Conditioning)<<

The coil is energized and the A/C Compressor Clutch engages(when voltage goes out Blk wire to sheet metal ground).

sooooooo

ala Connector Part Information

A/C Compressor Clutch Supply Voltage [also Circuit 59, how fancy is that??] is STILL dark green..we are getting closer...

It is Pin 18 on the C2 RED connector.

[pnhigg]

Thanks a bunch for the info.
I am still not quite sure I am 100% sure, and it was probably the way I asked the question.
So if I connect (beyond the junction) one dark green wire from the 92 harness to the a/c clutch the other will go to pin 18 on the red connector to signal the pcm to increase idle rpm, or do I connect it to terminal 17 the a/c signal wire?

Sorry about redundant questions, I just don't want to fry my pcm.


Thanks again for the help, and the attached list will be a great help.

Patrick

[r6z4o6]

Is what i am looking at, this is GM manual for a 91 C/K.

ONE THING, there appears to be a misprint on the first pic.
Halfway down the page, to the right of connector C223 the 59 circuit appears to change to light green(I assume it should have stayed dark green) as on the next page, the wire starts out as dark green again...)

As I understand the two diagrams, when you turn key ON "A/C HTR 25 AMP"[top left, top pic] is battery voltage down to the "A/C CLUTCH RELAY [bottom middle, bottom pic]. You press a/c button on thermostatic head unit, it grounds terminal 966 on head unit [top middle, bottom pic] and closes the "A/C CLUTCH RELAY" which then makes circuit 66 Light Green wire HOT with 12 volts. That 12volts goes THRU the "A/C PRESSURE CYCLING SWITCH" (assuming it is closed due to proper charge of freon) and out the other side, the 12 volts now travels thru Dark Green wire:

1.) 12 volts goes thru "A/C COMPRESSOR CLUTCH", and out the Black go ground, which engages hte clutch.
2.)12 volts goes back through the typo mentioned earlier, to the bottom pic and into Pin 1, Circuit 59 on "A/C CONTROLLER."
3.)12 volts goes to the back of "ECM CONNECTOR, pin B8 circuit 59.

I haven't gotten this far in my conversion, else i would tell ya if it fried my PCM or not!!!

In the link i gave a post ago if you go UP a directory and hit up the "00pinpcm.htm" file, it details circuit 59 as "A/C Status Signal" which sounds exactly like what you are looking for...I wish i had a really good GM manual for the NBS PCM...*le sigh*

Pin 18 is STILL Circuit 59, and it is STILL Dk Green...I didn't stick with wrenching long enough to get my L1, but i understand self control in putting 12 volts into the computer

This link is a really good read!!!!!
Final Steps for A/C - Relay/PCM control? Electronics gurus? - LS1TECH(It has another diagram as well in teh first post)

[r6z4o6]

PCM explosion, or cooling a/c?

[pnhigg]

I have been out of town.
I have the a/c working, but nothing is hooked into the pcm as of yet.
After finding out some more information and finding a good deal on a 145 amp alternator ($55 off a new van that will become a conversion)
I have decided to upgrade the alternator, wiring from the alt to batter, and clean up the wiring for my fans.
I will be doing all this at the same time I hook the a/c signal wire to the pcm.
I may not get it done this weekend as I am waiting on a 125amp fuse to come in the mail (alternator charge wire fuse), and I have got to get on the lake some time this weekend.
I will certianly post the progress notes when we find out.

Wish me luck.

[r6z4o6]

GOOD LUCK!

P.S i am verrrry interested in how you fabbed your A/C brackets on the original-style compressor.

[pnhigg]

Let me get all the bugs worked out, and I will talk to you about a set.

I can't seem to get the fans to come on, so I am still chasing

[pnhigg]

Alright, I need some help fellas.

I have a 5.3 in a 92 fullsize.

I have added a single electric fan.
I have it connected to what I understand to be the high speed fan signal (red connector #33)
Also from what I can tell the fan should come on at 200 and off at 195.

I also had the a/c wired to kick the fan on when the compressor was engaged, but I am getting nothing.

Anybody have any ideas.


I have a 75amp relay with 12 volts entering pole 30
87 to the fan
86 to a ignition on 12 volt source
85 pin 33 red connector on the pcm.

Any ideas why this isn't working.

[RedHeartbeat]

Did you have your tuner turn on the fan control in your PCM?