During an A/C system performance test, the air temperature at the center outlet duct is warm to slightly cool and the low- and high-side pressures on the manifold gauge set are both low.
All of the following could be the cause of these symptoms EXCEPT:
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Welcome to the Home of Motor Age Training Self-Study Guides for ASE...and now, Mitchell 1 ASE Test Preparation Guides!
Effective immediately, Mitchell 1 Guides are available for purchase on this site. Order online today or place your order by phone, 24 hours a day, Monday-Friday, at 800-240-1968. We look forward to hearing from you and wish you the best of luck on your upcoming test(s)!
Pass or Don't Pay
As a testament to our confidence in our study guides, we offer a money-back guarantee on both Motor Age Training Guides and Mitchell1 Test Guides.*
*Guides must be purchased during the current ASE testing season in order to qualify. Then, should you not pass, just send us a copy of your test results by July 30, 2008 and we'll refund the entire cost of your self-study guide, less S&H:
Motor Age Training for ASE Certification
PO Box 6310, Duluth, MN 55806-6310
"DON'T ASSUME ANYTHING
On GM trucks with electronic 4x4 systems, sometimes the 4x4 does not engage the Front Axle Gears. Check:
* Vacuum leaks - check vacuum lines going to and from the transfer case and the actuator servo unit commonly located under the battery tray. Vacuum leaks are notorious.
* Be sure the three-way vacuum switch connector on the transfer case is in the proper position; it has a one-way connection.
* If all the vacuum lines are OK, ensure the vacuum switch is OK. I have found problems with a stuck switch ball. For best results, remove the switch and visually check the ball on the bottom of the switch.
* The switch located on the front axle tells the TCM that the cable has pulled in the actuator. The TCM will then stop 4x4 light from flashing and will keep the light on steady to indicate that the front axle is in 4x4 mode. Be careful; do not assume that the front axle is actually turning. It doesn't always guarantee that the gears in the front axle are meshing. You may have damaged gear teeth."
Craig Burkhart, ASE Certified Master/L1 Technician
Hanna's Automotive, Massillon, OH
Benefit from the experience of your peers! Find helpful tips like this one from your fellow mechanics by visiting the Tech Tips section of www.motorage.com.
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