A/C Disable Settings

[WarWagon]

The #1 reason I got a tune and Hptuners - A/C and Cooling fan control.

I can say on a 2006 Trailblazer SS that the RPM cutout works independent of the TPS. It flat warms up the AC in the over 5K RPM range regardless of WOT or not. Changes to these RPM settings do work on this TBSS. This is seen by the clutch on the compressor kicking out via a test light to the compressor clutch wire.

Can anyone post with authority the actual redline of an AC compressor?
Overpressure concerns are solved with the high pressure kickout switch. (And other ways.)

So far 5500 RPM hasn't killed a compressor for me yet.

The WOT kickout killed a compressor clutch on a freeway on ramp with lots of smoke on my 85 Olds. High AC pressure, kick it out, and it could not spin the compressor back up thus burning up the clutch. So it was a little weak from being kicked out in this manner several times. (I replaced only the fried clutch and bearing not the entire compressor. Good thing it had it's own separate belt.) The WOT kickout leaves the highest starting torque load and high engine speeds on the AC clutch because all other times it has to cycle the clutch will leave more off time for the head pressure to come down and reduce starting torque needed. (And usually lower engine speed.) I think it is a bad idea to use WOT kickouts for the above reasons. (Unless there is a hard RPM limit then we are trading one part for another.)

I disagree that GM knows when to kick out the compressor. This is an old 1970's hot rod trick used later on underpowered cars. GM may have a proving grounds in AZ but they are from Michigan staring at snowbanks most of the year. Both the Fan % and AC cutout stock settings unnecessarily and noticeably reduce the AC ability. For example: 55 degree output air at idle in 110 + weather due to lack of fan use. Command more fan and the idle AC output temps cooled down. Must be fuel economy concerns and not wanting to add an extra extreme air temperature table just for AZ.

[5_Liter_Eater]

Can you verify with the AC clutch and AC disable WOT status bits that its working on the TBSS? Maybe it's working for us but the status bits are not working or something.

[WarWagon]

Can you verify with the AC clutch and AC disable WOT status bits that its working on the TBSS? Maybe it's working for us but the status bits are not working or something.

AC Clutch bit changes and AC Serial Cmd changes. I will have to change the WOT setting to test that bit. @ WOT clutch stays in till the kick out RPM. There could be a timer after this because it does not kick back in via RPM. It also could be due to the 60 degree weather out. Yet on review the removal of throttle and engine speed drop looks to kick it out as well as seen from 5200 RPM run up and drop offs.

See attached run frame 310-311 at WOT to see the RPM kick out the AC clutch.

[5_Liter_Eater]

Thanks for doing the test. What PCM is the '06 TBSS? E67? This may be a problem specific to the E40's.

There is a built in 6 second timer that we do not see in HPT. You can see it in EFI Live but there is no real reason to change it.

[WarWagon]

2006 Trailblazer SS, SSR, and GTO use the E40 ECM.
2007 TBSS has the E67 ECM.

6 second timer: Good info.

The ECM change cost after market fan kit & tune vendors $$ in R&D.

[C6 Houston]

Has any progress been mad on this?

[BennyHHR]

Bump for a solition.

Having the A/C stay on with my "no bank 2" kills the power!

[5_Liter_Eater]

Has anyone seen if anything's changed with 2.22? My car's down right now so I can't check.

[LBSBLOWN]

Bump, any news on this yet.

[5_Liter_Eater]

I'll see if I can test this evening. My current settings are:

Disable RPM = 4000
Re-Enable RPM = 2000

Disable TPS = 60%
Re-Enable TPS = 20%

If that does not work then I will try the settings Chris suggested in post #31.

Set the Disable RPM to something like 7000rpm and the Re-enable RPM to say 7200. Then set the TPS values to whatever TPS you want the AC to disable and re-enable. eg. 80 and 75.

[8850]

Better if the disable and particularly enable is rpm controlled. If you set it with TP control then when you let off throttle at 7000 rpm then compressor would come on at too high rpm. High rpm is what we are trying to avoid.

[5_Liter_Eater]

Like Chris said in the last page, there is another field that we don't see that defines how long it is to stay disabled for.

[LBSBLOWN]

Vehical is the 2005 GMC truck in my sig.
this is what I found durring test last night.

I monitored the AC clutch status and the AC WOT disable status bits,
I set disable to 3000rpm
re-enable to 2500rpm
TPS disable to 80%
TPS re-enable to 70%
I made three run from 30mph to 120mph
each time the AC compressor bit stayed on for a while but some where arond 4500rpm it would show off and stay off until the RPM dropped below 2500rpm at closed throttle.
But the AC WOT disable never changed, t allways says OK.

It seems that ether there is a 3 to 4 sec delay of the AC clutch disable or a Pressure switch is kicking it off line but once its off it will not re-enable until the RPM drops past 2500rpm with the throttle closed.

I did one pull from 0 to 120mph and all of first gear it stayed enabled but in secound at 4300rpm it shut off and stayed off until i lifted the thottle and the rpm dropped past 2500rpm.

[5_Liter_Eater]

I tested this last night with my settings and Chris' settings and could not get it to work. I never once saw the AC WOT Disable status bit change. Sure my AC clutch and AC pressure status bits changed but never the WOT disable.

[Ben Diss]

I tested this last night with my settings and Chris' settings and could not get it to work. I never once saw the AC WOT Disable status bit change. Sure my AC clutch and AC pressure status bits changed but never the WOT disable.

It sounds like your saying that the AC turned off, but the WOT status bit didn't change. Interesting. What settings did you use?

[5_Liter_Eater]

First I used TPS disable of 30 and re-enable of 20 and RPM disable of 4000 and re-enable of 2000. Then I used the settings Chris' settings of disable RPM 7000, re-enable of 7200, disable TPS of 30%, re-enable of 20%.

The AC clutch status bit turned on and off but nothing that really followed the WOT parameters.

[LBSBLOWN]

First I used TPS disable of 30 and re-enable of 20 and RPM disable of 4000 and re-enable of 2000. Then I used the settings Chris' settings of disable RPM 7000, re-enable of 7200, disable TPS of 30%, re-enable of 20%.

The AC clutch status bit turned on and off but nothing that really followed the WOT parameters.

basically what i have been seeing except for the fact that once the AC clutch statis goes to off it will stay there until the RPM drops below the re-enable rpm. but like you have seen the AC WOT statis never changes.

[Ben Diss]

This has got to be a bug. The "stock" settings for my '07 C6 are:

Disable RPM: 7083
Re-Enable RPM: 7083
Disable TPS: 200%
Re-Enable TPS: 197%

I'd like to make sure the compressor is not engaged when in PE mode. If I could get it to reliably disengage at 4000 RPM and >50% TPS I'd be happy.

[5_Liter_Eater]

I'd like to make sure the compressor is not engaged when in PE mode. If I could get it to reliably disengage at 4000 RPM and >50% TPS I'd be happy.

Ditto.

[gmtech16450yz]

Ok, this is interesting...

I just looked at an EFILive tuned '08 GMC Sierra 6.0 VMax ECM (E38) with both EFILive and HP Tuners programs and noticed a few weird things, AC disable/enable was one of them.
In EFILive the disable rpm is set to 4000 rpm, the re-enable is showing 3800 rpm. If you look at the same tune in HP Tuners it shows the opposite- disable shows 3800 rpm and re-enable shows 4000. What's up? Maybe this is a clue to what you guys were dealing with in this thread?