ac blinks 3 times

[luscombe8]

2000 blazer - Climate control - Press ac button and it blinks 3 times, compressor turns on, maybe 3 minutes later. Sometimes blinks 2 times, compressor turns on 1 min later. Cleaned the sensor in the headliner above the drivers side door with compressed air. R-134 is good. Temp control is all the way down to coldest setting. Will not start above 75 outside air temp unless you try it several times. Other times it starts right up. Looking for second sensor, is there one in the dash I can clean? Fuses, both 9 and 21 were checked with ignition off and are OK. Blend door is operating perfectly, the compressor is the only thing erratic. I think a sensor problem. Other opinions welcomed. Thanks . . .

[MT-2500]

You need to get into the body/AC control computers and read out readings and check for codes.
Has the battery or anything been bad or changed?
Also could be just low on gas/R134a.
With compressor jumped and running post back you low and high side readings at idle and at 2K.

With a ac recharging gauge set that has a low and high side gauge.
Like one of these.
http://www.ackits.com/merchant.mvc?S...ory_Co de=DIY

Low side should be close to 30 lbs.
If it is dropping under 25 lbs the switch will cycle or shut off compressor.

Post back pressure readings and AC control codes.

[luscombe8]

Thanks MT-2500,
The problem has been around since I purchased the car two years ago. I have replaced the battery, but the problem was there first. Now, as soon as I can figure out how to jumper the compressor, I will post the pressure settings. There is one connector on top of the compressor, with one green wire and one black. If the black is ground, then the green must be power. Maybe a wire from the battery to the green connection with the black side connected to ground while the car is running?

[luscombe8]

The manual does say that the ac will blink three times if it is not ready to turn on. they recommend opening a window and clearing out as much hot air as possible to lower the load on the system and to NOT place anything on the center dash because there is a sensor up there that is part of the system. Maybe it's the small black lightbuld shaped thing in the middle of the defrost vents on top of the dash? or is it the one in the left hand top of the dash speaker? anyway, I'll blow some compressed air over both of them to see if it helps. They system takes longer when the car has been in the sun, hmmm, maybe those things get too hot? Anyway, I'll try the jumper thing once I figure it out/

[MT-2500]

Jumper the green with a fused jumper to be safe.
Let us know pressure readings.
MT

[luscombe8]

MT,
With the compressor running, a/c on full, engine speed at idle the pressure was 42lbs. Raise the engine speed to 2K and the pressure was about 28lbs.
Is it normal for the pressure to drop when the engine speed increases?
Today was 88 degrees and the unit was sluggish to kick in (took about 45 min), but once it did start, it cooled normally. Shut the engine, went to lunch, the unit started right up and shut off. Pressed the ac button, blinked 3 times, then 3 min later, it started again.
Thanks,
JK

[MT-2500]

Originally Posted by luscombe8

MT,
With the compressor running, a/c on full, engine speed at idle the pressure was 42lbs. Raise the engine speed to 2K and the pressure was about 28lbs.
Is it normal for the pressure to drop when the engine speed increases?
Today was 88 degrees and the unit was sluggish to kick in (took about 45 min), but once it did start, it cooled normally. Shut the engine, went to lunch, the unit started right up and shut off. Pressed the ac button, blinked 3 times, then 3 min later, it started again.
Thanks,
JK

Yes it is normal for low side to go down when engine rpm is raised.
But we need the high side reading to.
42 idle and 28 at 2K rpm is fairly good low side pressure.

If the light is blinking 3 times or blinking and it takes a long time to turn on compressor.
You need to get it on a Body/AC capable scanner and get codes and read out what is going on.
Post back codes.
MT

[luscombe8]

MT,
I have found a service bulletin NHTSA ID #10009984 in a complaint from a customer about her 2001 Blazer. The a/c works intermittently and they have posted a service bulletin about transfer case oil in the hvac vacuum lines.
The shops around here voice objections to trying to pull hvac codes (they can't do it) and have referred me back to a dealer.
Bad experiences with this dealer are causing me to keep searching on my own. If I could purchase a code reader, I'd do it myself, but no luck in finding an aftermarket tool.
I'll try to locate vacuum lines for this thing and examine them for oil contamination.
Only as a last resort will I pay the $165 the dealer wants for a "diagnosis".
I will post my findings later this weekend.
Thanks

[luscombe8]

Problem solved . . .
Years of working in the body shop gave me a few friends I could talk to and they put me in touch with a mechanic at the local Chevy dealer. This led to an assurance that a bad experience would not be repeated and I made an appointment to have them diagnose the car.
After a few minutes, they told me the AMBIENT AIR TEMPERATURE SENSOR was bad and the total bill for diagnosis and part and labor for the repair would be about $140,
Done, lets see if this will last, it makes sense, after reviewing the symptoms. Many thanks to MT for his guidance in analyzing this problem, your forum really works.
Should anyone need help with Austin Healeys, I have 30+ years experience with them.
Best,
John

[MT-2500]

Thanks for posting back how it went.
Glad you found a good dealer tech that knowed his stuff.
Good Luck
MT