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Ask Chad Farhat Your Own Question
Chad Farhat
Chad Farhat, ASE Certified Technician A6 - Electrical / Electronic systems A7 - Heating & Electronic systems
Category: GM
Satisfied Customers: 3431
Experience:  Owner at Carolina Auto Service & Sales , 20 years Experience in Foreign & Domestic vehicles
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2002 silverado 5.3L a/c works great on ghway-blows warm air

Customer Question

2002 silverado 5.3L a/c works great on highway-blows warm air city driving
Submitted: 1 year ago.
Category: GM
Expert:  Chad Farhat replied 1 year ago.

Hi, I' m Chad. Welcome to JustAnswer. I' m reviewing your question now, and I will be post back with your reply ASAP

Customer: replied 1 year ago.
Expert:  Chad Farhat replied 1 year ago.

1-how many miles on truck ?

2-have you checked Freon levels ? if you low it will do that , does the compressor cycles a lot at idle or city driving ?

3-did you hook up some a/c gauges and tested the system , you need to see 25 to 50 psi on low side gauges while running and 150 175 psi tops on high , have you checked that ? if you seeing over 175 on high we have a restriction , if you seeing the low not pulling down to at least 50 and it stays at 60 70 and when you rev up the engine it goes down to 30 lets say , then you have a weak compressor .

3- if clutch fan is good and running, that leaves a restriction in the system like ( condenser itself ,evaporator ) or a weak compressor at low speed ?

you can tell all that by looking at the gauges if you have some ?

Customer: replied 1 year ago.
to check fan clutch
2 have gauges all seems fin
3 compressor does not cycle often enough to concern me
4 mixing door?
5 vacume ?
6 180000
7 i am an aircraft mechanic but cant fix this sucker
Expert:  Chad Farhat replied 1 year ago.

oh wow thats cool, it is easier for me with tech like you then the average person on skills and know how :) , ok no problem

if all the gauges reading within specs ( what were your numbers please and what is the avg temp where the truck is at ) ?

than yes vacuum & blend doors will cause this issue and cause a blend door to move , would you say ,when give it a kick down ,do you feel like a burst of cold air just rushed

thru, i think you know what i mean, like a door got open , you even hear it in dash sometimes if you listen close

1- fan clutch when engaged , using hard gloves , can you stop it with finger ?

2- do you have access to a smoke machine that we can test for vacuum leaks

3- do you hear any noise coming from dash, i m assuming you dont cause you would inspected that by now , but i have to ask :)

Customer: replied 1 year ago.
temp-200 deg no overheat issues
86 and humid-truck sitting outside idleing will cool all day in the driveway duct temp 76 deg
no unusal noises when passing on highway-when i reach the first city light-warm air until i shut off engine and restart-or reach a speed of over 40mph
you really want me to stick my hand in the fan??? ok then-i cannot stop the fan at idle
where would i find the mixing door-under glove box? and where can i check vacume at i have a vacume tester-no smoke machine guess i light a cigar but its not christmas -thats the time my wife lets me smoke them
Customer: replied 1 year ago.
side bar-always alot of evaporator moisture leaking out-seems typical-yes?
Expert:  Chad Farhat replied 1 year ago.

hahaah, your funny man

yes moisture is good , actually means running good ,

now you can get to the actuators and take them off and kind try to stick your finger in there not much room and feel the door , the blend doors you cant see it is inside that heater box under the dash board ,where your blower, evaporator and actuator and blend doors are , like that diagrams

but each actuator in that diagrams is connected to one of them, temp door, mode door ,re circulation door

do you see the 2 small nipples coming out of the box , is there vacuum lines there attached , did you ever looked under there

Expert:  Chad Farhat replied 1 year ago.

do you have a/c manual controls on dash correct ?

if you pull the a/c control unit in dash, it should have like a vacuum line assembly connector in back of it ?

can you pull that controller off and look for me , i guess we can test from there with vacuum pump , since no smoke machine

Customer: replied 1 year ago.
taking it apart now gotta go to work soon so were done for today another side bar our shop rate is 155 per hour-why do I only get 25.25?????? dont answer that should of went to college instead of military aircraft school
Expert:  Chad Farhat replied 1 year ago.

i agree you should get at least 75 per hour :)

I can make a mistake on a car , but you cant on a plane :) so it should be worth way more

no problem man , i m online daily from 10 am till 12 pm

during day i have shop might be slower to answer back but i usually do within 30 min , i will help you with if i can , but you and me we should figure it out

just come back to post and ask me and i will see your reply and we can go back and forth until we figure it out .


Hope I was helpful to you ,

A Positive Rating is Much Appreciated

This Post Will Stay Open For You to Come Back and ask me any Follow up Questions you may have on this issue Even after you Rate Me.

Thank You
Chad Farhat ( aka -Customer)
ASE Certified Technician

Customer: replied 1 year ago.
evap box not totally apart yet but I see no vacume lines at all electrical connectors only will totally disassemble tomorrow I owe I owe off to work I go
Expert:  Chad Farhat replied 1 year ago.

i suspected that , this system is not vacuum actuated motor for blend doors

it is electrical motor that moves them, so we have a bad blend door or bad actuator ? unless you have auto control unit?

just confirm one thing you do have a manual or auto control a/c unit in the dash?

we will talk tomorrow