1999 Chevy Silverado A/C ?

[BADA$$69]

Has plenty of freon, blows cold air momentarily, then warm air. Sometimes cold lasts a while and other times won't blow cold at all. Does anyone have any idea what it could be?
Thanks in advance for any help.

[87 STEPPER]

My '99 Tahoe was doing the same thing the other day and it was my pressure sw. connector lose i had to stop twice and fiddle with it and it hasnt done it any more.

It could also be your pressure sw. going bad but i'd ck the connector 1st.

It's located on the receiver dryer on the firewall on the passangers side.

[Huck]

The low pressure switch is supposed to turn the unit on and off to prevent freezing which will give you the symptoms you descirbe. The switch is screwed into the silver canister on the pss side of the firewall. As 87Stepper mentions--Make sure the connection is good first---then if not, I would put a new switch in--it's very basic with no loss of freion--just unscrew it and screw in the replacement. My 2000 had that issue and I brought it to a mechanic buddy who is expert on A/C---no biggie.

[BADA$$69]

Thanks guys!

[87 STEPPER]

Did ya get r fixed?

[BADA$$69]

Not yet. Going to have to replace the switch.

[Eyegore]

Not to steal this thread, but I'm having problem under the dash/glove box where the damper keeps opening and closing robbing me of a/c. What causes this problem and how do you fix?

[BADA$$69]

Alright Guys,

I've replaced the pressure switch, $32. Same thing! Anybody have any other ideas?

Sweaten in May,

Thanks,

BADA$$69

[old Rusty C10]

do you hear any vacuum leaks in the cab?? maybe the baffle door swings open due to bad vacuum if not then you need to have the pressure checked. HAVE IT DONE RIGHT dont buy those cans with the guage for like $20 at advanced the guage there dont work right

[04 orange]

If this is a new body style 99, then check your cabin air filters. They could be so clogged that they are making the a/c freeze up. They are to the left of the blower motor, there's is a small panel you take down, and there will be two of them inside.

[BACKYARD88]

Actuators are the most common problem with these style trucks. I sell on average 8-10 a week at a small dealership. The temp. actuators are on the top and bottom of the case, mode actuator is on the drivers side of the case with a cam attached, and the recirc. actuator is behind the glove box.

[BADA$$69]

Thanks BY88.
Anyway you can be a little clearer on the location of these actuators?

Thanks again,
BA69

[BACKYARD88]

In the illustration you are looking from the firewall side. Please forgive me for my previous statement about the actuators, I had forgotten that the 99 only has one temp. actuator. It is #16 in the illustration. If there's a cover under your dash it'll have to come off first, then the actuator should be easily noticeable, 1 electrical connector, two screws. I'll post up some more info for you in a minuet.

(1) Heater Core Cover
(2) Heater Core
(3) A/C Defroster Seal
(4) Upper HVAC Module Case
(5) Dash Seal
(6) A/C Valve
(7) Heater/Defroster Valve
(8) Temperature Valve
(9) A/C Valve Lever
(10) Mode Valve Actuator
(11) Heater/Defroster Valve Lever
(12) Mode Valve Cam
(13) Lower HVAC Module Case
(14) Rear Heater Duct Seal
(15) Temperature Valve Actuator Screw
(16) Temperature Valve Actuator
(17) HVAC Module Wiring Harness
(18) Blower Motor Resistor/Relay Assembly
(19) Blower Motor Acoustic Insulator
(20) Blower Motor
(21) Blower Motor Fan
(22) Passenger Compartment Air Filter Access Door
(23) Dash Seal
(24) Evaporator Block Seal
(25) Evaporator Core
(26) Passenger Compartment Air Filters
(27) Air Inlet Valve
(28) Air Inlet Housing
(29) Air Inlet Housing Seal
(30) Air Inlet Actuator
(31) Heater Core Pipe Seal

[BACKYARD88]

The actuator is a part number 52474810 list price is $74.40.
I can't say with 100% certainty that the actuator is the problem, all I can say is that it is the most common problem for the concern you are describing. Here's the replacement procedure. Whatever you do don't turn the key on with the actuator plugged in and not connected, if you do it will turn out of range and once this happens it is no longer any good. Good luck, and if you have any more questions or would like me to fax you the testing procedures and schematics let me know.

Temperature Actuator Replacement
Removal Procedure
Remove the instrument panel hush panel .



Disconnect the electrical connector (8) from the temperature actuator (9).



Remove the temperature actuator retaining screws.



Remove the temperature actuator.
Installation Procedure




Install the temperature actuator.



Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

Install the temperature actuator retaining screws.

Tighten
Tighten the screws to 1.6 N·m (14 lb in)





Connect the electrical connector (8) to the temperature actuator (9).
Install the instrument panel hush panel.