Jaysz28

iTrader: (30)

Bone stock ls1/T56 in a 82 Camaro. Using the variable compressor.

Got around to hooking up the AC this week. The system held a vacuum and took the charge just fine, but the compressor would not kick on.

Time to start chasing wires.

I found a great thread that had a perfect diagram for me to follow.

https://www.thirdgen.org/forums/ltx-...ml#post4345712

I verified each wire and discovered a dead short on the green wire to the compressor from the relay. Plus the relay was not wired correctly.

So I started over with a new relay. Here is how I have it wired up.

Red connector
14) AC pressure sensor signal to pin C on the pressure sensor
17) AC request signal 12v from the hvac panel
18) AC Clutch supply voltage to relay #87 and to the green wire on the compressor
43) AC Clutch relay control to relay #85
57) reference ground to pin A on the pressure sensor

Blue Connector
45) 5v to pin B on the pressure sensor.

still, I have no ac.

I have 12v at pin 17 with the ac on.

If I ground relay #85, ac compressor will run. The fans come on and the idle comes up. I left the low pressure switch on the ground side and let it run for awhile and saw vent temps at 50* while idling in my garage with 90* ambient temps.

I cannot get the PCM to turn on the ac.(ie ground the relay)

My only two thoughts are this.

1) The PCM reference ground is not hooked up???? I am not certain which reference ground to look at.

2) Possibly the AC is turned off in the tune. I will cough up the $100 tonight and buy some credits for my HP tuners.

Does anyone else have any input? It seems as if the PCM is doing its job when I ground the relay.

A possible work around I have thought of is to piggy back the AC relay #86 and #30 power (with a fuse) off of the AC request signal under the hood. Then just leave the relay grounded (through the 3rd gen low pressure switch). That way the relay is only energized when the ac is requested.

Not my favorite option, as I would rather have the switch on the ground side of things.

Again, any suggestions from those of you that are more experienced with wiring than I am.

Once this is tackled, time for an alignment, window tint and cruise control. If the AC stays this cold, this will be a great, fun daily driver!

kenney001

iTrader: (1)

I would check for continuity between Red 57 (low reference) and ground (I grounded my PCM to the back of the drivers head).

I would then unpin Red 14 from the ECM connector, and measure voltage between that wire and ground (back of cylinder head or wherever your ECM ground is). you should get something between .1-1.8v with key on engine off. If not, you may have a faulty sensor.

Take the pigtail off the high pressure sensor and make sure you have 5v at the connector with key on (Brown or Grey wire), and make sure you have continuity between ground and low reference (Black wire). The Red wire should have continuity with Red 14 (AC pressure sensor signal). Make double sure the red wire is not hooked to the 5v, it was a mistake I almost made the first time.

If all of that passes, Id look at the PCM as the problem. Im not familiar with tuning, so it may be disabled.

If you can ground the relay, and everything works as it should, its all about the high pressure sensor, PCM, or wiring between those two.

Jaysz28

iTrader: (30)

Thank you for the very detailed reply

I have checked for continuity to everything but the ground to 57 as you stated. I should look at that again.

I will also double check the 5v reference to the grey wire at Pin B.

Heading out to download the tune now and if that checks out, then on to chasing wires some more.

It is tough to do this in person, let alone over the internet..... so I do appreciate the response!

-jason

Jaysz28

iTrader: (30)

Ok, verified 5v at the sensor on Pin B (grey wire)

For fun, I checked the ground on the purple wire. Nothing

With the key off, there is continuity to ground, with about 4 ohms of resistance.

I will pull the red connector and check for continuity as you suggested.

One thing I found when I downloaded the tune, is its a truck PCM? but its flashed for a 2000 camaro convertible????

not certain if I am chasing a ghost at this rate. It *might* just be software related.

but I will check out pin 57 low reference to ground.

thanks

-jason

Jaysz28

iTrader: (30)

Well just to update my own thread......

I go out to log what the PCM is seeing. I just turn the key on to see what the PCM is seeing. I slide the lever over to max ac. I see the ac request turn 'yes' on the scanner. I have 1.17 v for the sensor.

then out of nowhere, I hear the distinct 'tink' of the ac clutch engaging.

AC clutch engaged turns yes, ac active turns yes.

I am freaking out..... what just happened.

I turned the key off, turn off the ac. start the car

start logging.

ac sensor = 1.17v
ac fitted = yes
ac requested = yes
ac active = yes
ac clutch engaged = yes!

and its blowing cold ac!!!!!!

unreal

and I am not really certain what I've done besides what I have posted.

so it works....... maybe tomorrow it won't, or it will work fine until I take it back to the ac shop for them to check the pressures and make certain everything is good.

I can book my alignment now though.... w00t

thanks for the support TGO. I found most of my answers searching, so I count that as support!

-jason

Jaysz28

iTrader: (30)

so now it isn't working.

I verified the 4 grounds at the PCM on both the red and blue connectors pin 1 and 40.

I have not checked pin 57 continuity to ground yet.

Pin 43 is supplying 12v+ to the relay, not a ground signal. If it is supposed to be a 12v+ signal, I can make that work by grounding the opposite side of the relay. The diagram does not read that way to me though.

so close yet so far.

kenney001

iTrader: (1)

You should NOT have 12v from pin 43. Thats wrong and would definitely cause the relay to not close.

Did you pull the pin out of the ecm connector and test that way or did you tie into the wire coming off pin 43 somehow. You may have a short somewhere that causes that wire to run 12v and not the PCM.

Jaysz28

iTrader: (30)

I did not pull the pin. I can almost see the relay from the PCM. the wire is only about 24" long or so. I soldered and heat shrinked it when I hooked it up.

Same goes for the compressor supply voltage to pin 18. Just 24" or so of wire to the relay.

I completely wired the relay as a stand alone piece to keep the issues to a minimum.

no other circuit shares that pin, unlike pin 57 which is also the low reference wire for the IAT sensor and the ac pressure sensor. I did verify continuity between the iat and the pressure sensor, as well as to pin 57 itself.

I wish I had another PCM to flash to rule that out as a possible problem.