AC compressor not turning after ABS delete - Chevy Impala SS Forum
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post #1 of 81 (permalink) Old 02-24-2018, 08:58 PM Thread Starter
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AC compressor not turning after ABS delete

Maybe just a coincidence, but after doing the delete, and a timing chain update, and a new battery, the clutch on the compressor wont engage normally.

Trying to do the troubleshoot, following the fact manual, looks like DTC's 66,67,68 but my OBDII reader dosent show DTC's only P codes. Changed relay in underhood center. No dice. Followed manual and can engage clutch and make AC run fine by jumping the relay out.

The AC Refrig Sensor is a 3 wire so cant jump it , and don't know how to check it.

When running AC pressures are fine. Verified that the control line from the relay back to the pcm appears to be working by applying B+ to it an verifing its passing voltage.

The two possibilities I see are the Sensor has died or theres a problem with the PCM. Until I can get a DTC code im just guessing.

Any thoughts would be appreciated.

95 Impala , LQ9/LS3 Swap. BTR Stage 3 with 11.5 comp., DGGM.
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post #2 of 81 (permalink) Old 02-24-2018, 10:20 PM
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Check the little white plastic thingy near the opti harness connector on pass. side for corrosion/damage.

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post #3 of 81 (permalink) Old 02-24-2018, 10:22 PM
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I would check for bent pins in the connector first. Check for voltage in the A/C call wire. Make sure the high and low pressure switches are functioning properly. The switches should both be closed if the pressures are correct. The low side switch is on the accumulator, and the high side switch is usually on the compressor itself.

Start with the low side switch, and check for battery voltage at the call wire. Once you find B+ at the output of the switch, go to the high side switch, and check for voltage on the wire from the low pressure switch. Next check for B+ at the output of the high side switch. Check for B+ at the input of the A/C clutch. Check for ground at the black wire of the clutch solenoid. If all of these are working, you should get the clutch to activate.

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post #4 of 81 (permalink) Old 02-24-2018, 10:59 PM Thread Starter
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Slow, Im running a MSD Opti, its got that long connecting wire going back up to the fuel rail area. So , white thingy is throwing me off


Fred, yep working through those. Thanks, tomorrow another try.
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post #5 of 81 (permalink) Old 02-25-2018, 12:54 AM
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Hope this helps somewhat

Sensor Ground Black to PCM "B" 6

Sensor 5v Gray to PCM "B" 28

There is no high pressure switch on the compressor.
PCM control va transducer as you mentioned in your first post.
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LS7 T56 6 Speed Wagon
Katech cam , 550 rwhp
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Last edited by 95wagon; 02-25-2018 at 12:56 AM.
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post #6 of 81 (permalink) Old 02-25-2018, 06:37 PM Thread Starter
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Another day,

Put in a new Clutch relay. Nothing.

Checked F6 to B21 , continuity good.

E6 to D8 continuity good.

Ill do B6 and B28 tomorrow.

Just for info, I jumped the E8 to F6 , hooked up the gauges and pumped in 12 oz of 134. Blows real cold with compressor running full time no cycling.

Should I probe 452 and 416 with AC on, key on ? expect to see 5 volt ?

I have a spare programmed PCM , might throw that in and see what happens.

Am I correct, that if the system were working correctly, I could jump the cycling switch A to B and the compressor kick in ?

My suspicions are Sensor bad , or PCM has puked.

Thanks for any help


BTW All references are to the middle pic posted above. Ive got both 95 and 96 , full original shop manuals.

And also, Hooked up my OBDII software , only code is the same one Ive had for years, P1661, EGR delete, and other stuff in PCM programmed by PCM for less.

95 Impala , LQ9/LS3 Swap. BTR Stage 3 with 11.5 comp., DGGM.

Last edited by VF1000R; 02-25-2018 at 06:42 PM. Reason: more info
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post #7 of 81 (permalink) Old 02-25-2018, 10:30 PM
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See caps below


Quote:
Originally Posted by VF1000R View Post
Another day,

Put in a new Clutch relay. Nothing.

Checked F6 to B21 , continuity good.

E6 to D8 continuity good.

Ill do B6 and B28 tomorrow.

Just for info, I jumped the E8 to F6 , hooked up the gauges and pumped in 12 oz of 134. Blows real cold with compressor running full time no cycling.

Should I probe 452 and 416 with AC on, key on ? expect to see 5 volt ?
YES YOU WOULD. THEY ALSO FEED MANY SENSORS SO IF THE CAR IS RUNNING , I WOULD SUSPECT THIS IS NOT YOUR ISSUE

I have a spare programmed PCM , might throw that in and see what happens.

Am I correct, that if the system were working correctly, I could jump the cycling switch A to B and the compressor kick in ?
EXCEPT THERE ARE MANY PARAMETERS |THE PCM MUST SEE BEFORE ALLOWING THE CLUTCH TO ENGAGE

My suspicions are Sensor bad , or PCM has puked.
READ THROUGH THE MANUAL, THERE ARE MANY CONDITIONS YOU MUST MEET BEFORE CLUTCH ON IS COMMANDED
THERE IS ALSO A PRESSURE VS VOLTS CHART FOR THE TRANSDUCER SO YOU CAN CHECK THE VOLTAGE ON 380.

IF YOU HAVE VOLTAGE AT B1 YOU ARE GOOD

IF YOU GROUND 459 AT D8 AND THE CLUTCH COMES ON, THE PCM IS NOT COMMANDING




Thanks for any help


BTW All references are to the middle pic posted above. Ive got both 95 and 96 , full original shop manuals.

And also, Hooked up my OBDII software , only code is the same one Ive had for years, P1661, EGR delete, and other stuff in PCM programmed by PCM for less.


The First
LS7 T56 6 Speed Wagon
Katech cam , 550 rwhp
11.79 @ 120.65


LS7 T56 drag video
My Wagon
My W-31 Cutlass
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post #8 of 81 (permalink) Old 02-25-2018, 10:49 PM
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Power steering pressure switch OK ?


The First
LS7 T56 6 Speed Wagon
Katech cam , 550 rwhp
11.79 @ 120.65


LS7 T56 drag video
My Wagon
My W-31 Cutlass
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post #9 of 81 (permalink) Old 02-26-2018, 12:27 PM Thread Starter
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PS switch OK

B1 has power


Now here we go. 459 to B8. I was not wanting to probe the small wire, so , I used a fine strand jumper wire and shoved it down in E6 then reinstalled the relay on top of it.

Turn the key on with AC commanded on. Go out ant touch jumper wire to ground and i can tell the clutch is activating. Release ground wire, go start engine. Touch jumper wire to ground and Clutch engages and stays engaged after removing jumper wire.

AC is operating. Turn engine off for several seconds then restart and no clutch engagement. Re attach jumper for about 1 second and clutch engages and all runs good. Jumper is not attached.

Turn AC off inside , clutch disengages. Turn AC back on, clutch does not engage. Ground jumper wire , clutch engages.

I am confused about 1 thing. Reference the AC clutch relay.

Should F8 to E6 show continuity between those pins on the uninstalled relay ? Mine does not, nor does my new one and AC had been working up till last November.

Thanks,
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post #10 of 81 (permalink) Old 02-26-2018, 01:24 PM
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One would sure think it should.
I can get you a "number" from my car when I get home.
that part of my AC is still stock.

Just spitballin here.

I have run into deals where a relay or clutch would not pull in but would stay from bad connections not carrying full current.

When it was clutch it was excess clearance and the voltage drop on the high current side was enough that it needed help.
That, though would show as your relay coming in but clutch not engaging till 12 volts was offered directly to clutch.
When it was relay not coming in there was excessive resistance on the lower current side of the relay.

Once had a 24 relay in a 12 volt box and never looked close enough
Again, the above scenarios WERE not LT1 B body.

If no one has got you actual relay resistance numbers by the end of the day I will.


The First
LS7 T56 6 Speed Wagon
Katech cam , 550 rwhp
11.79 @ 120.65


LS7 T56 drag video
My Wagon
My W-31 Cutlass
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