No AC at all - nada, zero, zip

[newbievueowner]

O.K, normally I would look this up on my service manual CD but I don't have it here at home (it's at my parents house for some reason) so I need to ask my fellow Vue owners that have the knowledge.

I tried to use my AC for the 1st time yesterday and it didn't work at all, not even slightly cool air, just the same temp as the outside air.

My question is, when the AC button is on are both electric fans supposed to be running? I know the comressor is supposed to start running and mine doesn't turn on. I started it up tonight to see (after reading the other AC threads) and apparently the fans are both supposed to turn on? Is this correct? Does this also apply when the vehicle is cold? Or does the vehicle have to be up to full operating temp? I have no fans or clutch engagement on the compressor with a cold engine.

It's a 2006 Vue V6. I checked for leaks with a black light and couldn't see anything green leaking. It worked perfectly fine last summer. A little guidance would be appreciated. Sounds like it could be a bad realy or fuse to me or something electrical. Tx

[far2grumpy]

What should happen - based on reading many Vue AC docs ...

Press the AC button (with HVAC fan switch 1 - 4) - LED lighted indicates AC request signal was sent to BCM. If TVX sensor does not see a freeze-up condition - BCM forwards the AC request to PCM. If PCM detects presence of around 40 psi of low-side pressure - a command is sent to compressor clutch relay and to cooling fan relays.

More or less.

[fdryer]

^ ^ What he said. ^ ^ Based on no fans or clutch engagement, its either the main a/c fuse or the system leaked since the last time it was used. If you only did a cursory inspection with a black light, look again but at everything. If the service valve caps were left loose then refrigerant can easily leak out. Examine the rear and underside of the compressor as sources of dye stains. Pick a start point and follow the plumbing with the uv light carefully in the dark as it goes to each component through the engine compartment; the inlet and outlet fittings on the firewall next to the heater hoses are the beginning and end points of the entire a/c system. The txv and evaporator coils reside behind the two fittings and not usually prone to leaking but anywhere in the engine bay has the bulk of the a/c system for close inspection.

Static (standby) pressures of sealed a/c systems will vary in direct proportion to outside temperatures. If outside temps are in the 60's then gas pressure will be around 60psi, 95F - 95psi. Once operating, pressures separate into two different numbers. Any leak that releases refrigerant until pressure drops below 40psi is detected by the pressure sensor and sends a disable signal to the ecm to prevent compressor and fan operation. The cooling fans will still run if coolant over heats.

[newbievueowner]

I will check again but I tried to follow most of the lines and couldn't see anything. Checked under the compressor as this is supposedly a known leak point and could not see any green phosforesence (sp?).

So if I don't have at least 40 psi on the low side then the system won't cycle at all. I will have to put the gauge on and see what I have.

Are there any other fuse/realy locations for the AC other than whats in the fuse box under the hood?

Oxidation on aluminum (because it's white) really stands out with the black light though.....

[TheVue]

I had a problem with the AC in my 2007. Pressing the AC light would turn on the little light on the AC switch but nothing else. It turned out the 40 pin connector at the foot well was the problem. It can cause many problems including no AC. Take a look at this thread and read post number 3.

http://www.saturnfans.com/forums/sho....php?t=165718#

The purple wire that controls the AC had come loose. I reconnected the wire and its been fine ever since. You may have an entirely different problem, but it's worth a look.

I have the original PDF for this document but it is too big to post on the forums. Private message me with your email if you want it.

Good luck.

[newbievueowner]

Thanks for the additional info, something else to look at. I will first check the line pressure on the LP side to ensure I have more than the minimum and go from there.

[newbievueowner]

Just to be 100% clear, the sequence specified in posts #2/3 would also apply with a totally cold engine correct (ie: fans are supposed to start running when AC is commanded provided minimum line pressure is met) or no?

[far2grumpy]

Originally Posted by newbievueowner

Just to be 100% clear, the sequence specified in posts #2/3 would also apply with a totally cold engine correct (ie: fans are supposed to start running when AC is commanded provided minimum line pressure is met) or no?

Yes sir ... I tried mine this am with cold engine and fans run (low) as soon as AC was activated.

[newbievueowner]

Is there another fuse/fuseible link/relay for the AC other than what's in the box in the engine bay? I'll start with the real easy checks first. lol

[far2grumpy]

Originally Posted by newbievueowner

Is there another fuse/fuseible link/relay for the AC other than what's in the box in the engine bay? I'll start with the real easy checks first. lol

I've included thumbnail for AC compressor and cooling fans wiring diagrams.

One item not depicted on compressor diagram is a temperature switch attached to side of compressor which is in series with the clutch engage path.

You could check the switch and simulate part of the PCM's job by remove the AC CLUTCH RLY and putting a jumper across pins 30 and 87 with engine running and AC switch set to ON.

If the clutch engages ... don't permit the compressor to run for more than a few seconds - unless the cooling fans are on.

If compressor runs with the bypass you can assume the PCM is not happy ... either because AC request is not reaching PCM or the AC pressure is not adequate to satisfy the pressure sensor.

[newbievueowner]

All I know thus far is the PCM is not happy. Jumped 30/87 and the compressor kicks on. Raining and windy so further investigation will have to wait. I'll check the pressure on the low side next I guess. What's min pressure supposed to be again? 40 or 50 psi?

[far2grumpy]

Originally Posted by newbievueowner

All I know thus far is the PCM is not happy. Jumped 30/87 and the compressor kicks on. Raining and windy so further investigation will have to wait. I'll check the pressure on the low side next I guess. What's min pressure supposed to be again? 40 or 50 psi?

There is a 10 amp AC fuse in center IP ... I believe if it were bad you wouldn't see the LED come on in AC request switch though.

The pressure sensor will not enable if pressure is less than 39 psi. I've attached the complete extract:

A/C Refrigerant Pressure Sensor

The A/C refrigerant pressure sensor is a 3 wire piezoelectric pressure transducer. A 5-volt reference, low reference, and signal circuits enable the sensor to operate. The A/C pressure signal can be between 0-5 volts. When the A/C refrigerant pressure is low, the signal value is near 0 volts. When the A/C refrigerant pressure is high, the signal value is near 5 volts.

The A/C refrigerant pressure sensor protects the A/C system from operating when an excessively high or low pressure condition exists.

The engine control module (ECM) or powertrain control module (PCM) disables the compressor clutch under the following conditions:

L66/3.5L

The A/C high side pressure is more than 2929 kPa (495 psi). The clutch will be enabled after the high side pressure decreases to less than 1376 kPa (200 psi). A/C low side pressure is less than 2706 kPa (39 psi). The clutch will be enabled or will allow engagement again after the low side pressure increases to more than 2941 kPa (43 psi).

[newbievueowner]

O.K, there is something strange going on here.....

I tried the AC today with vehicle warmed up - the compressor clutch engaged, BUT I still don't get any cold AC (not even coolish) air.

[far2grumpy]

That is strange - I can't think of a scenario that would run compressor under or over pressure (other than a clutch relay jumper).

Can you hang a set of gages on the silly thing?

[newbievueowner]

I have more info now. The R134 adapters finally arrived and I put the old manifold gauge set on. 50 PSI on the low side and only 70 PSI on the high side? Even more perplexing now. And the compressor clutch engages! But only when the vehicle is hot, not when stone cold and the AC is put on. What does the manual say are possible scenario's/causes for this condition?

[far2grumpy]

Originally Posted by newbievueowner

I have more info now. The R134 adapters finally arrived and I put the old manifold gauge set on. 50 PSI on the low side and only 70 PSI on the high side? Even more perplexing now. And the compressor clutch engages! But only when the vehicle is hot, not when stone cold and the AC is put on. What does the manual say are possible scenario's/causes for this condition?

Why does compressor run when engine is hot ... its probably because the hot engine (radiator) heats the co-located AC condensor causing a corresponding increase in pressure ... enough to trip the sensor.

According to the thumbnail ... 50 and 70 psi put you in Zone B - which typically indicates low charge or compressor problems.

I've attached the complete extracts for performance test and Zone B - the other Zone extracts are available if you'd like to see.

[newbievueowner]

Thanks for the attachments. I was searching on AC issues and saw another post by Fdryer indicating that the pressure reading needs to be taken at 2000 rpm. Is this correct? What are the conditions to take the low and high side pressures? Maybe this is why I got such low pressure on the high side?

[far2grumpy]

Originally Posted by newbievueowner

Thanks for the attachments. I was searching on AC issues and saw another post by Fdryer indicating that the pressure reading needs to be taken at 2000 rpm. Is this correct? What are the conditions to take the low and high side pressures? Maybe this is why I got such low pressure on the high side?

The standard dealership go / no-go test is completed at idle RPM as outlined in the performance test procedures. The truth is if the AC does not cool at idle RPM - say, in city traffic - who gives a damn about running at 2k RPM?

If the AC fails to meet the minimum requirements as outlined in the attachment - a technician (DIY'er) could move on to Zone's A, B, C or D - depending on the thumbnail matrix.

I attached Zone B to earlier post and have attached A, C and D to this post.

Keep in mind - these Zone tests are keyed to the AC Performance test document previously attached. There are dozens of other tests but the GM extracts are part of a self-contained assessment of the typical Vue AC system.

[fdryer]

When you observe unusually low high side pressure at idle or 2k rpm with low to normal low side pressure, this indicates lost refrigerant, a leak. Idle rpm with a full charge and cold temperature setting forces the variable displacement compressor to run from its initial low displacement to full displacement. The high side pressure should ramp up to whatever the chart says it should be. The txv maintains low side pressure whether the engine is idling, accelerating, or at high rpm. The high side will build up pressure as reserve to bank all refrigerant that isn't between the evap outlet from the txv to the compressor suction port. With high displacement/full amount of refrigerant, high side pressures build up. With a leak, the high side pressure reflects the lack of refrigerant to build up pressure - the leak that already occurred. When raising rpm to 2k, one of two things should occur to explain one of three modes; pressures rise, rise a little more than low side, remain low or equal to low side.

Raising rpm to 2k would build up pressure to reflect the reserve compressed refrigerant being packed into the volume between the compressor output port and the inlet to the txv. If a leak occurred, this high pressure won't be so high. A faulty compressor can also make less pressure; faulty internal mechanism regulating displacement may not allow full displacement to occur so output volume is reduced and less pressure is generated that's constantly being bled off as the txv maintains feed pressure to control evap temps. Compress less refrigerant either from a leak or from a faulty compressor and the output pressure is lower than expected. No one will see this during idle speed pressure monitoring and 2k rpm is needed to see if high side pressures change. Careful monitoring and comparison of pressures at idle and 2k rpm can help differentiate a compressor failure from a leak. With all things given, the most likely issue is and usually a leak. Very few compressors fail and the ones that do most likely fail from less than professional servicing when a/c cooling is first detected. One part of Saturn service manuals during troubleshooting will start by removing all refrigerant and leak testing before proceeding any further. This accomplishes two criteria; determining if a leak exists and following up with repairs or refilling with the exact amount of R134a and monitoring pressures before letting the vehicle out the service bay.

Home servicing without all the a/c equipment requires a different approach to troubleshooting based on past issues and history of outcomes. The majority of all loss of cooling issues has always been the leak that very few accept because R134a is colorless and odorless unless a large amount is released at once and seen/smelled while releasing refrigerant. The silent leak evades all but the seasoned a/c tech with the overall perspective.

While not encouraging a jump to conclusion, simply injecting at least a half pound of R134a into this system while observing the pressure gauges will display a higher high side pressure while interior temps begins to drop...........to indicate the leak that already occurred and to verify that bringing up R134a amounts will restore cooling as opposed to a faulty compressor. A faulty compressor won't raise high side pressures. I can confirm this with an attempt to restore a VW Jetta ('93/'94?) with no change in high side pressures before and after injecting one pound of R134a with dye. The VW was determined to be too old to justify repairing since it already has about 180k miles with two clutch replacements. Even with free labor, the cost of parts would be too close to the diminished value of the car.

[BobbyP]

90's VW AC parts must be expensive...

Looking over the Performance chart, the measured temps seem way too high.

Shouldn't the measured temps be around 30-40 degrees on an average car?

I've seen them as low as 25 degrees with my duct thermometer...

Today my Escape in Denver was having a challenge to cool the SUV in 99 degree weather...