1998 Chevy Blazer A/C works at idle heater is on the rest o

Tiny
MICKER11
  • MEMBER
  • 1998 CHEVROLET BLAZER
  • V8
  • 2WD
  • AUTOMATIC
  • 153,451 MILES
When I start the vehicle the a/c comes on and works fine when I rev up the engine the a/c stops working and the heater comes on. The compressor is still engaged. Driving down the road the heater is on. At a stop a/c starts working again I suspected a vacuum problem so I replaced the vac hoses under the hood. The check valve is working as it should. When the engine is off I can disconnect the vac line at the vac reservoir, it seems to be holding vacuum. I removed the lower inside panel and all of the vacuum pots (that I can see) seem to be working and holding. When I am driving down the road there is no problem with air shifting say from defrost to panel etc. The gauge readings on the high side and the low side are correct
Do you
have the same problem?
Yes
No
Monday, June 21st, 2010 AT 5:08 PM

17 Replies

Tiny
DOCFIXIT
  • EXPERT
Hi Automatic climet control or manual? Would you post low/high gague readings
Thanks for donate
Was this
answer
helpful?
Yes
No
Tuesday, June 22nd, 2010 AT 10:15 AM
Tiny
RACEFAN966
  • EXPERT
Ok before I be of much helps I need to know if you have automatic A/C or manual a/c. Get back to me so I help you find the problem.
Was this
answer
helpful?
Yes
No
Tuesday, June 22nd, 2010 AT 10:17 AM
Tiny
MICKER11
  • MEMBER
The a/c is automatic I will have to reconnect the gauges to give exact pressure readings but the compressor is not disengaging at high rpms it is running full time even when I am driving down the road( I suspect that it has something to do with the door that switches from heat to cool maybe?) Thanks
Was this
answer
helpful?
Yes
No
Tuesday, June 22nd, 2010 AT 10:38 AM
Tiny
RACEFAN966
  • EXPERT
I suspect one of the ambient temp sensors but before we go to checking that I would like the A/C guage readings on the high and low side. Provide the outside air temp at the time you check it ok. Thanks.
Was this
answer
helpful?
Yes
No
Wednesday, June 23rd, 2010 AT 9:50 AM
Tiny
MICKER11
  • MEMBER
Ambient temp is 93f gauge pressures are 240 high side 47 low side
Was this
answer
helpful?
Yes
No
Wednesday, June 23rd, 2010 AT 6:10 PM
Tiny
RACEFAN966
  • EXPERT
Ok first thing is the pressure is not correct at that temp. At 93 deg it should be low 29-37 and high 337 to 374. So I would say you are low on freon so lets get it full first and then go from there. I would say maybe one can.
Was this
answer
helpful?
Yes
No
Thursday, June 24th, 2010 AT 10:13 AM
Tiny
MICKER11
  • MEMBER
Ok I added about 1/2 to 3/4 can low side 37 high side 350 I checked 1 more thing. The temp of the air at the panel inside is 70 degrees at idle. When I rev the engine and hold it at 3000 rpm for a couple of minutes the air temp is 134 f. The receiver dryer is cold and dripping condensation
Was this
answer
helpful?
Yes
No
Thursday, June 24th, 2010 AT 12:05 PM
Tiny
RACEFAN966
  • EXPERT
Ok so do you have a digital multi meter? I would like to check a couple of temp sensors.
Was this
answer
helpful?
Yes
No
Friday, June 25th, 2010 AT 10:02 AM
Tiny
MICKER11
  • MEMBER
Sorry for the delay in the response. My meter seemed to be broken. I went into town and bought another one. Ready for the next tests thanks
Was this
answer
helpful?
Yes
No
Sunday, June 27th, 2010 AT 4:37 PM
Tiny
RACEFAN966
  • EXPERT
On the right side (passenger) of the radiator support there is the outside ambient temp sensor. You need to look for two wires DK Green with a white stripe and a black wire. Now with you meter simply unplug it and ohm the sensor. Now get back to me with the ohms and the air temp at the time you check it ok. We will go from there.
Was this
answer
helpful?
Yes
No
Tuesday, June 29th, 2010 AT 11:05 AM
Tiny
MICKER11
  • MEMBER
I located a small black box looking item mounted to the bottom of the radiator support 2 wires to it I assume that I found the right part. Has a yellow and black wire running to it (maybe the wire is faded?) The reading to it is 998 with the ohm meter set at 2000 ohm setting. The outside temp is 80 degrees thanks
Was this
answer
helpful?
Yes
No
Wednesday, June 30th, 2010 AT 10:55 AM
Tiny
RACEFAN966
  • EXPERT
Ok if that was the ambient temp sensor then it way out of spec. Now I have included a pic of where it is and what it should look like just to be sure.

Location


http://www.2carpros.com/forum/automotive_pictures/249564_Outside_Temp_Sensors_2.jpg



Sensor


http://www.2carpros.com/forum/automotive_pictures/249564_276571_1.jpg

Was this
answer
helpful?
Yes
No
Wednesday, June 30th, 2010 AT 11:18 AM
Tiny
MICKER11
  • MEMBER
Thanks for the pic I had tested the wrong part. The sensor gave no reading on the 200 or 2k settings. On the 20k setting it gave a reading of 7.36 at 90 degrees im sure I tested the right part this time (green and black wire running to it) thanks
Was this
answer
helpful?
Yes
No
Wednesday, June 30th, 2010 AT 4:00 PM
Tiny
RACEFAN966
  • EXPERT
Ok at that temp it should read about 3900 ohms so it looks like that sensor is no good. When you tested it you just unplugged it and ohmed the sensor not the wire harness? If that is correct then it is bad. These are available at you local parts stores so there is no need to go to the dealer unless there price is better. Let me know how it goes.
Was this
answer
helpful?
Yes
No
Thursday, July 1st, 2010 AT 11:14 AM
Tiny
MICKER11
  • MEMBER
Sorry for the delay in getting back to you I live 30 miles out of town went in to order the part they sent the wrong one. I have the right one now installed it. Same problem. I ohmed the sensor and it reads the same as the old one (within a few ohms ) I noticed that it also senses for the outside temp reading on the mirror ( when I unplug it and turn on the key the thermometer doesnt work. It is reading the correct outside temp (presently 93 degrees). Thanks
Was this
answer
helpful?
Yes
No
Thursday, July 8th, 2010 AT 6:54 PM
Tiny
RACEFAN966
  • EXPERT
Ok do you know where any of the inside temp sensors are? This is crazy according to the readings you gave that should have been it. Anyway lets move on and see what we can find.
Was this
answer
helpful?
Yes
No
Saturday, July 10th, 2010 AT 9:06 AM
Tiny
DOCFIXIT
  • EXPERT
Have you tried using in manual mode? Does A/C stay cool
Was this
answer
helpful?
Yes
No
Saturday, July 10th, 2010 AT 11:38 AM

Please login or register to post a reply.

Recommended Guides