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trying to find a high pressure switch

monty101 on Thu July 25, 2013 11:42 AM User is offlineView users profile

Year: 1997
Make: buick
Model: lesabre
Engine Size: 3.8
Refrigerant Type: 134a
Ambient Temp: 95
Pressure Low: 55
Pressure High: 125
Country of Origin: United States

My lesabre has climate control. It is going to cost too much to replace the programmer that is not sending the compressor clutch request input to the 62 pin on the ecm.

I have a choice of wiring up a manual switch hooked to a 12 volt source to this 62 pin or bypassing the ecm on running the ac manually. I don't need the climate control advantages and
I have decided to bypass the ecm on runnning the compressor. So,

I need to bypass the computer controlled pressure switch

1)I will need to install a low pressure switch in my accumulator. The switch I need is available for 22 bucks from autozone and my accumulator has a schrader valve on it to mount it

2)It has a 3 pin computer controlled pressure switch that is now installed in the hose plumbing that bolts to the compressor. I need a 2 pin high pressure (425 psi cut off) ac switch
that I can install in that plumbing after I remove the 3 pin switch.

I intend to wire in the hot wire I have already installed that is hooked up to a 12 volt source to one of the pins on that high pressure switch and connect the other pin on the switch to the compressor relay. That will not let the compressor stay engaged if the pressure is too high.

I intend to hook up a ground wire to one of the pins in the 2 pin low pressure switch on the accumulator and hook the other pin to the other pin on the compressor relay. That will not let the compressor engage unless there is enough pressure.

This should allow me to turn on the ac and it should cycle properly. The climate control does allow you to manually adjust the fan speed and does allow you to turn on the heater by
moving the vents to the heater coil. Just won't be able to set the temperature and expect the ac and fan to incease intensity based on the inside air, outside air and desired air temp.

Anybody know where I can get a ac 2 pin high pressure switch that has the correct threads to replace the 3 pin computer controlled pressure switch on a 1997 lesabre. Any thoughts would
be welcome. I have found that there is a high pressure switch that can be installed on a compressor but my four seasons compressor is new and it has no place on the back of it to install a high pressure switch. These are held in with a snap ring. I am not sure if there is a compressor available I could get that would have such a hookup on it that would work on my 1997 lesabre.

I have found one that you can get from china part # INTL-Y170 that appears to right for what I need. see link below:

http://intl2008.en.alibaba.com/product/1080811603-209941637/2_PIN_Pressure_Switch_Sensor_for_GM_car_models_A_C_Refrigerant_Pressure_Sensor_Air_Conditioning_Transducer_Switch_Pressostat.html

but I have not found where I can buy it in the usa.

Edited: Thu July 25, 2013 at 11:56 AM by monty101

monty101 on Thu July 25, 2013 8:02 PM User is offlineView users profile

I think I may need a different compressor if I want to have a 2 pin high pressure switch. It appears that 4season "hd" are the compressors that have a place to install such a switch.

I am thinking that a 4 seasons hd57955 compressor might fit on a 1997 Lesabre. It appears the only difference
is the hd57955 has a high pressure switch on the back of it. It fits a 1996 buick roadmaster and appears to be
the same size and has the same mounting flanges as the 4seasons ht57994 which is what I am currently running.

Does anybody know if I can switch compressors from a 96 roadmaster to a 1997 lesabre and install a 2 pin pressure switch and wire it up as I have stated and get the clutch to engage manually??

GM Tech on Thu July 25, 2013 10:22 PM User is offline

I'd never attempt what you are trying to do- I'd put a boneyard control head in ($35) or fix your old one- probably a bad solder joint- done a few like yours- certainly never mess up a good system- pressure switches are not used with variable stroke compressors- a pressure transducer is used to turn off compressor when pressure is below 47psi, toturn off compressor when pressure is above 425 and to turn on electric fans on low speed when pressure is above 175 and high speed when above 250-- so you want to give up all that control??? Never try it is my advice. The compressor destrokes to avert freeze-up, no low side switch needed...

There are small online tech businesses out there who will fix your old control head- just google it----

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

monty101 on Fri July 26, 2013 11:00 AM User is offlineView users profile

Thank you for answering my inquiry. You advice is greatly appreciated. These AC systems cost more to fix than the car
is worth. What you going to do?? Its hot here in Texas.....Got so hot my fat dog had a heat stroke last week. Don't need
that to happen to wife who's driving that car.

I suspect there are a lot of cars in the salvage yard now because it costs to much to fix some of the fancy new things that
we take for granted......I found a lesabre out in the salvage yard a while back. I needed a neutral switch relay that is between
the starter and ignition. I had found it was easy to pull that relay. Just pull the speaker covers off and it is right there. So, I
pulled it off thinking that it would not be in the junk yard because it would not start because it needed this relay. Wrong.....

The relay was bad and I had to get a new one and it started right up. I do know that the book does not state that the easy
way to pull that relay is to pull the speaker covers. They give you a lot of hours to do the job which indicates to me they believe
it necessary to pull the dash which is the only way after looking down in there you can get to that relay......

Guess that owner just junked it instead of fixing it. This new ac "climate control" stuff is extremely expensive for old cars like
this 97 Lesabre. It may just become a Texas winter car.

The last programmer i bought cost over a hundred bucks in a salvage yard. That was about 3 years ago. That is a lot cheaper
than a new one that is about 750 bucks from gm. I can get a new one from rockauto for 204....I suspect programmer will fix the
vacuum leak it has but I am not so sure it will fix the problem associated with turning on the clutch but it might.

The problem with used programmer is you will break the nipples off trying to detach the vacuum noses. I have learned that that
outside hose hookup is often times they whole problem when you have a vaccum leak. I have drilled it out and bypassed it in the
past. It's easy to do. I do know its blowing air out the def now and that means it has a vaccum leak. I will check but I suspect
the vacuum is not leaking up front under the battery where its hooked in so it probably the programmer.

So, this weekend, I am going to pull the program controller out and fix the vacuum leak it has. I suspect I will have to bypass
the outside hose connections and attach the vacuum hoses up directly to the hose nipples inside the module. Then I will look
as you have suggested for a part in the salvage yard if fixing the vacuum line leak does not miraculously cause it to send the
compressor clutch request input to the ecm. I will also look for a loose wire in the programmer and solider it back if necessary.

Right now the prior owner hooked up a toggle switch that goes directly to the relay . It does engage the compressor clutch and turn on the ac.
If I have to I may get a low pressure switch and run that through a low pressure switch so at least it does not come on unless the compressor
has 134a in it. I guess if I run it without a high pressure switch it will get a lot colder but I doubt it will cause icing here in Texas.
At least with a low pressure switch it won't burn up the new compressor if for some reason it loses all it 134a.

I may contact PCM for less and ask them about that pin on the ecm that receives the imput from the programmer that tells it that
the ac compressor should engage as long as the pressure sensor signal allows it to. I believe its a 12 volt current that goes to it
and I suspect they will know. Locating that pin and wiring up a hot wire to a switch might solve my problem......

94RX-7 on Sat July 27, 2013 12:13 PM User is offline

Quote
Originally posted by: monty101

I have decided to bypass the ecm on runnning the compressor.

What? Why? Seems like the simplest thing to do and still retain proper operation.

How are you going to get the condenser/radiator fans to operate properly? Doesn't the ECM turn those on when the refrigerant pressure gets high enough?

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