I purchased my Blazer on Thanksgiving and was told that the AC works. Now it has warmed up and the AC definetly does not work.

Bought R134a and pressure gage/hose set. Hooked up to low pressure side and found 20psi. Pressured system to 40psi and think that is enough to start the compressor running. It did not start. Checked both fuses at interior fuse block and 2 fuses under the hood, as well as the relay. All checked good.

Pulled the electrical connector at compressor and it had no voltage present with AC set to MAX and fan on high. Compressor coil measured 4 Ohms, which seems reasonable.

What can I check next?

 

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Have you attempted to jumper your compressor clutch to verify that the system works when the clutch is engaged?

I know my old dodge intrepid had a problem where the compressor would never engage, but when jumpered, it would cool like mad. The culprit was a $20 pressure transducer that tells the PCM that the pressure is either too low or too high to try to save the compressor from shreading itself.

Also, can't leave out the obvious... Have you checked all of the fuses? Do you have the A/C button lit up on the dash? Please don't let either of these questions offend you. I am just stating the obvious.

 

I have checked all interior and under the hood fuses. They are all good.

I actually had to go out and check to see that I didn't have a seperate AC switch on the dash. I have missed the obvious before!

Looking for a pressure transducer seems like a good plan. I'll get on that one Saturday.

As for the compressor, I will try to jump it directly and see if it fires up. I believe the coil is good since it measured 4 Ohms. At 12 Volts that would give a holding current of 3 Amps. Seems like good numbers to me.

 

Hmm.. Ah yes, manual controls. Sorry. I have had the auto climate control in my last 4 vehicles and I forgot that the manual controls have a separate mode area with a blue line for the A/C zone controls.

1st thing I would do is jumper the compressor clutch and see if it gets cool inside. If it doesn't get cold or the compressor sounds noisy, you have other problems.

If the inside gets cooled down with the compressor hotwired, let me know and I'll see what info I can dig up on the checks that the PCM does to turn on the compressor.

BTW, if you refilled it, how did you do this without the compressor running? I believe that you must refill it on the low side with the compressor running inorder to get a proper pressure reading.

 

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Jumped the compressor and it works.

Found the pressure transducer located on the dryer and it read open. Jumped the plug to close the loop and compressor started to run!

Now that I can start the AC, I will hook up the pressure gage to the low side and check for proper readings. Acording to instructions the gage should read between 25 and 40 PSI for opperation.


THANKS SWARTLKK

 

No problem. Glad I could help!

You don't want to ride around with the compressor or pressure transducer hotwired for too long. This should be used as a refilling only workaround. You may not have to replace the pressure transducer cause it may just cut off the clutch based on low pressure in the line. Refill it to the specs that came with your kit and then hook everything back up the way it normally is and give it a check.

Good luck and keep us informed.

 

The switch you are jumping is a cycling switch. It also acts as a safety switch to keep the compressor from coming on when it's low on refrigerant. Jumping the switch should only be for 'test purposes'. Continued operation will lead to catastrophic compressor failure.

To test the switch, it should cycle the compressor OFF at about 22 psi and back on at about 45 psi. With a low system, this will happen quickly. If it's really low, the compressor may not come on at all. I suspect that's what's happening in your case.

You will most likely need some leak detection, repair and then proper recharge.

Hope this helps.

 

I am having a very similar problem. I can jump the pressure switch connector that is on the receiver and the AC works, it blows cold too. I connected a gauge from a refill can to the low pressure port and its reading 45psi when the compresor is running on max cool.

Do you think the pressure switch is bad? Do you have to evacuate the system to replace this switch? I believe this is the low pressure switch? Is there something else that could cause this? There maybe some damage to the condensor from some front end damage, but i figure any major damage and I would not be getting 45 psi. The AC worked fine last summer, before the damage. Also, I don't remember if this happen last year or not, but running the AC with the pressure switch connector shorted, run the temp gauge on the dash up to right under 210 .. it normaly never goes past the 1st 1/4 mark (160 i think)

Thanks,
Kevin
95 Chevy Blazer
88 Mazda RX-7 10th anniversary
03 Mazda Protege5

 

Sounds like a bad cycling switch. You can replace it without removing refrigerant. It threads onto a port that has a schrader, so you will loose a little refrigerant, but not enough to worry about. Just be sure to wear gloves. Liquid refrigerant can burn!!