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Discussion Starter #1
First let me say I lover my ride. I have found nothing basically wrong with the machine.

On the Air Conditioning issue.

I was able to inspect four 05 SSR’s including mine, for the problem with the compressor clutch cutting in and out on a 10 to 12 second interval.
10 seconds on and about 10 seconds off on all four 05 SSR’s .

On mine I was told everything was fine and rapid clutch operation was to
provide better fuel mileage. My clutch has been on and off over 70,000
times so far. BAD ANSWER!

The next dealer conceded the clutch operation was not correct. After talking
to the factory they were allowed to replace the expansion valve.
Replacement of the expansion valve provided a ‘clutch on’ of about 15 fold;
now the clutch would be engaged for about 150 seconds and off for about
30 seconds on full fan, a hot day, and windows down. Still unacceptable!

The expansion valve is an interesting device. It is used to moderate
the spray of the cooling liquid with a variable orifice in the expansion coil.
Its operation is complex as it maintains a predetermined temperature
in the expansion coil located under the dash.

A safety device also located in the expansion coil under the dash is something referred to as a “cycle switch”. It is not a switch! IT IS A THERMISTOR!
A thermistor is a resistor that has a related positive or negative going
resistance due to temperature. A current is fed to the thermistor and the variation of this current determines when an open collector switch in the on- board-computer turns the clutch on and off. My expansion coil never freezes.
I have never found water dripping from the outlet water tube.

All thermistors are not created equal. Thermistors that have 1% tolerances are
expensive and we all know GM is in the business of cost cutting. The variation in tolerances of this device explains why some of our SSR’s report no problems
with the A/C. They got lucky!

T H E F I X


The fix is in proper programming of the on-board-computer to compensate
for variations in the thermistor tolerances allowing this device to provide freeze
protection without interrupting the normal operation of the A/C system.
Changing out the thermistor is difficult as the whole dash must be deconstructed and then a new thermistor will not guarantee a fix. The programming must be allowed to correct for variations in characteristics of the thermistor and its placement in the expansion core.

This is not rocket science. Why did GM give dealers this problem when a factory ‘twek’ in programming compensates for the two variables of the thermistor; tolerances and location? What kind of crap is this? A high end vehicle with this problem is unacceptable!

As for the future of GM all 150 of my friends and maybe their friends, know about the problems with my SSR. They also know it will not be corrected for
whatever reason!
 

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:willy: Oh my if it blows cool air on a hot day ForgetAboutit. Having a Chevrolet dealer screwing with the dash and such will make things a lot worse. If it stops cooling all together then I say get it fixed. You must not have owned many GM cars in the past. LIVE WITH IT or get rid of it. The SSR is unique and has some quirks.
 

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Discussion Starter #3
Mr. Ricochet:

Are you a Dealer for GM? You sound like the two that I have visited.

GM has been in business for a hundred years and at some point technical excellence is to be expected; especially on a ‘high end’ vehicle.

This explanation and complaint is not about the SSR, it is about the air conditioning in the vehicle. Is not about SSR quirks or other engineering problems. Air conditioning is basic and has little to do with the vehicle in
which it is installed.

This complaint is about quality control at GM, computer programming of a portion of the on-board-computer, and technical expertise at dealerships.
It is about finding and fixing a problem that is not limited to my SSR.
 

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No, I just know better and im trying to pass along good solid advice. I have been down this path before and sometimes its better to let sleeping dogs lay where they are. Gms version of a "high end" car/truck means YOU pay the "high end" and GM (& Most other makers of goods today) pays the VERY CHEAPEST suppliers they can find and hope it lasts through the 3/36 warranty. Thats where the real problems come from any item you purchase is only as good as the quality of the sum of its parts. You just can't "fix" or improve anything with the same part you are replacing, unless that part is truly defective, or the replacement part has been upgraded in some way.
 

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replaced

Dealer drove mine for two weeks and noticed similar A/C problems and replaced compressor on their own, seems to have fixed the situation.
Might want to mention this to your dealer...or not...
 

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I've found that the best greeting for a SSR owner is "keep the roof down":ssr :ssr
:party
Soooooooo.....Air Conditioning......Whats That????
 

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Discussion Starter #10
Mr. OP

The A/C system works perfectly when the clutch is engaged.

The compressor has a non-serviceable self- protection switch that is activated during
high heat conditions. The symptoms indicated this switch was implicated and changing
the compressor was the only solution. However, after changing the expansion valve
causing a 15-fold clutch engaged time, changed my mind.

Study indicates the system is properly sized, including the compressor, and other system
components. This information narrowed the suspect components that have control
over the disengagement of the clutch. The WOT and the convertible top both have
control; and the Thermistor(cycle switch).

The problem is cyclic in nature; it can be timed with a watch. Therefore the WOT system
and the convertible top system are eliminated. This leave only the THERMISTOR.

There is no information on the thermistor.
 

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Understanding Why.....

Thermistors, also known as RTDs (Resistance Temperature Devices) typically don't go "bad" unless they have a catatstrophic failure. Their nature is to respond quickly to temperature changes with a linear resistance change. It is a robust device that has "standard" resistance/temperature curves. If it drifts from the original specification, it is typically to shift the entire calibration either up or down scale by a few degrees. This is rare (1x10 to the -6th or better), even on cheap RTDs. Open or shorted thermistors are more common failure modes, but the computer should log a fault for that when it does BIT (Built-In-Test) on power-up.

You can add hysterisis to the system and slow down the response of the RTD by insulating it a little. This will stop the short cycling, but make the temperature regulation unacceptably lousy.

Taken from the '05 Service Manual:

Compressor engagement will occur if:
A/C compressor is selected to on. - and -
The Evaporator Temp Sensor is above 32 F. - and -
Engine speed must be greater than 550 RPM. - and -
Coolant temp is below 253F. - and -
A/C system pressure is between 70 and 410 psi.

Once engaged, the compressor clutch will disengage if:
Throttle position is 100%. - or-
Evap temp is less than 32 F. - or -
A/C pressure is above 429 psi. - or -
Engine coolant temp is above 253 F. - or -
A/C compressor temp switch (internal) opens. - or -
Transmission shift. - or -
PCM detects excessive torque load. - or -
PCM detects insufficient idle quality. - or -
PCM detects hard launch condition.

I'm not going to guess where your short cycling is coming from. There are way too many factors involved, including your individual ambient temp that impacts the evap temp a lot.

Sorry for the deep dive, but you need to be armed with all the facts you can get on this one. I think there may be an opportunity for the service tech to show you the pressure data.

Mike
 

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Discussion Starter #12
Mr. Mike in AZ.

Yes, I agree and have read and know something about thermistors.

The thermistor has been part of GM cooling for some time. Several years
ago a problem developed in a GM cooling system similar to the one being
described in this discussion. The fix was to pull the thermistor out to a new
position in the expansion core. Cycling stopped-problem solved.
 

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Richardaaa said:
Mr. Ricochet:

Are you a Dealer for GM? You sound like the two that I have visited.

GM has been in business for a hundred years and at some point technical excellence is to be expected; especially on a ‘high end’ vehicle.

This explanation and complaint is not about the SSR, it is about the air conditioning in the vehicle. Is not about SSR quirks or other engineering problems. Air conditioning is basic and has little to do with the vehicle in
which it is installed.

This complaint is about quality control at GM, computer programming of a portion of the on-board-computer, and technical expertise at dealerships.
It is about finding and fixing a problem that is not limited to my SSR.
I live in a 7-8 months per year aircon environment - haven't had a bit of trouble yet. Oh, and I'm not a dealer - of anything.
 

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Richardaaa said:
Mr. Mike in AZ.

Yes, I agree and have read and know something about thermistors.

The thermistor has been part of GM cooling for some time. Several years
ago a problem developed in a GM cooling system similar to the one being
described in this discussion. The fix was to pull the thermistor out to a new
position in the expansion core. Cycling stopped-problem solved.
Richardaaaa,

We're on the same page here. Moving the thermistor away from the evap core will "desensitize" the system. There is surely a "sweet spot" location that gives acceptable temperature regulation without being to sluggish. Not an exact science at this point, as putting the RTD up against the fins will give you possibly the coldest possible temp, but will result in the shortest cycle time for the compressor. Moving it farther away will, conversely, give you a much more reasonable duty cyccle on the compressor, but brings with it wide swings in evap temp..... and resulting air temperatures. I've had the latter in a vehicle and hated it.

The "middle ground" is where we really want to be. My '05 had a little too long of a cycle and allowed too big of air temp swings. My '06 has a much shorter cycle and hods temp better, but is somewhat annoying for anyone that watches for short cycling.......

I'm going to wait until May before I complain about it to the Dealer.... if then.

Regards,

Mike
 
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