A/C Selection
Thread Starter
Racer
Joined: Nov 2005
Posts: 374
Likes: 0
From: Corona CA - "An Armed Society is a Polite Scociety"
A/C Selection
When running the A/C on my 98 I can't select from vents to floor to defrost.
Is this vacuum, electric or mechanicly operated and where should I start?
Is it better for me to take it to the shop or tackle it myself?
Is this vacuum, electric or mechanicly operated and where should I start?
Is it better for me to take it to the shop or tackle it myself?
Le Mans Master
Joined: May 2007
Posts: 5,383
Likes: 6
From: hagerstown md
St. Jude Donor '08-'09
Sounds like you have the dreaded vacuum leak. Start by removing the battery, and seeing if you have any broken lines under there. The vacuum line is a hard plastic line inside the large wire loom.
Search Bill Curlee posts for pics and a write up. He did a great write up with pics.
If it isn't under there, you'll have to find out if you have vacuum from the engine to the canister. If you take the inner fender out on the fron passengers side, you can see where the lines come into the car. You can start the car, pull the line from the engine off the vacuum solenoid and see there.
If you have none there, then the line has either broken, or came off the back of the intake. A real PIA to get to. One guy did it without pulling the intake, but that's the only one I've heard of. Everyone else has to unbolt the intake. Not a big project. Just have to make sure you torque it back down correctly.
There have been some really good write ups, just search and you'll find plenty.
Need any more help, shoot me a PM. I've already had to do it, and I'll be glad to help any way I can.
Search Bill Curlee posts for pics and a write up. He did a great write up with pics.
If it isn't under there, you'll have to find out if you have vacuum from the engine to the canister. If you take the inner fender out on the fron passengers side, you can see where the lines come into the car. You can start the car, pull the line from the engine off the vacuum solenoid and see there.
If you have none there, then the line has either broken, or came off the back of the intake. A real PIA to get to. One guy did it without pulling the intake, but that's the only one I've heard of. Everyone else has to unbolt the intake. Not a big project. Just have to make sure you torque it back down correctly.
There have been some really good write ups, just search and you'll find plenty.
Need any more help, shoot me a PM. I've already had to do it, and I'll be glad to help any way I can.
Thread Starter
Racer
Joined: Nov 2005
Posts: 374
Likes: 0
From: Corona CA - "An Armed Society is a Polite Scociety"
Sounds like you have the dreaded vacuum leak. Start by removing the battery, and seeing if you have any broken lines under there. The vacuum line is a hard plastic line inside the large wire loom.
Search Bill Curlee posts for pics and a write up. He did a great write up with pics.
If it isn't under there, you'll have to find out if you have vacuum from the engine to the canister. If you take the inner fender out on the fron passengers side, you can see where the lines come into the car. You can start the car, pull the line from the engine off the vacuum solenoid and see there.
If you have none there, then the line has either broken, or came off the back of the intake. A real PIA to get to. One guy did it without pulling the intake, but that's the only one I've heard of. Everyone else has to unbolt the intake. Not a big project. Just have to make sure you torque it back down correctly.
There have been some really good write ups, just search and you'll find plenty.
Need any more help, shoot me a PM. I've already had to do it, and I'll be glad to help any way I can.
Search Bill Curlee posts for pics and a write up. He did a great write up with pics.
If it isn't under there, you'll have to find out if you have vacuum from the engine to the canister. If you take the inner fender out on the fron passengers side, you can see where the lines come into the car. You can start the car, pull the line from the engine off the vacuum solenoid and see there.
If you have none there, then the line has either broken, or came off the back of the intake. A real PIA to get to. One guy did it without pulling the intake, but that's the only one I've heard of. Everyone else has to unbolt the intake. Not a big project. Just have to make sure you torque it back down correctly.
There have been some really good write ups, just search and you'll find plenty.
Need any more help, shoot me a PM. I've already had to do it, and I'll be glad to help any way I can.
I scaned for Bill's write up but couldn't find it. I'll try again tonight if I didn't find the cause right off.
Thanks for the info.
I'll post if I find the cause.
Instructor
Joined: Aug 2004
Posts: 139
Likes: 0
From: statesboro ga
I ran all new lines from the intake to the check valve, from the check valve to the canister and put on a new check valve and still can't control my vents. I also checked under the passenger dash and everything was ok...I still can't figure it out...
Pro
Joined: Sep 2007
Posts: 735
Likes: 7
From: Bucks County Pa
AC Problem
Other items to check
There are 3 mode valves connected to the module, the mode valve, the defrost valve, and the air door valve. All work on vacuum. From your description the mode valve is suspect, or a line could have dislodged from the mode valve or control head. Also even though you replaced the lines, did you check the tank itself for leaks, they've been known to get holes in them. And the control head could also be defective. Below is a diagnostic to direct you through the additional checks, and a Mode Valve replacement instruct in case you need it. If you need more help, post.
Good Luck
++++++++++++++++++++++++++++++++++
Air Delivery Improper
Step
Action
Value(s)
Yes
No
DEFINITION: Air flow is not being delivered from the proper mode outlet which was requested by the operator.
1
Where you sent here from the HVAC System Check?
--
Go to Step 2
Go to HVAC System Check
2
Remove the I/P RH lower insulator. Refer to Closeout/Insulator Panel Replacement - Instrument Panel (I/P) Lower in Instrument Panel, Gauges and Console.
Disconnect the I/P harness vacuum connector from the HVAC module violet vacuum (source) line.
Connect a vacuum gauge to the I/P harness vacuum line.
Start the engine and allow the engine to idle.
Measure the vacuum at the I/P harness (engine source) vacuum line.
Is the vacuum reading within the specified value?
10-17 in Hg
Go to Step 3
Go to Step 4
3
Turn OFF the engine.
Inspect the vacuum reading at the I/P harness (engine source) vacuum line.
Does the vacuum reading hold steady?
--
Go to Step 11
Go to Step 6
4
Remove the RH front wheelhouse filler panel. Refer to Wheelhouse Filler Replacement in Body Front End.
Disconnect the engine harness vacuum connector from the vacuum tank check valve.
Connect a vacuum gauge to the engine harness vacuum (source) line.
Start the engine and allow the engine to idle.
Measure the vacuum at the engine harness vacuum (source) line.
Is the vacuum reading within the specified value?
10-17 in Hg
Go to Step 6
Go to Step 5
5
Repair the leak or restriction in the engine harness vacuum (source) line.
Is the repair complete?
--
Go to Step 20
--
6
Connect a vacuum gauge to the vehicle interior end of the I/P harness vacuum line.
Remove the RH front wheelhouse filler panel.
Disconnect the I/P harness vacuum connector from the vacuum tank check valve.
Connect a hand vacuum pump to the vehicle exterior end of the I/P harness vacuum line.
Apply 15-20 inches of vacuum to the line.
Measure the vacuum on the vacuum gauge inside the vehicle.
Is the vacuum reading the same as the amount of vacuum applied and does the vacuum reading hold steady?
--
Go to Step 8
Go to Step 7
7
Repair the leak or restriction in the I/P harness vacuum (engine source) line.
Is the repair complete?
--
Go to Step 20
--
8
Disconnect the vacuum tank check valve from the vacuum tank.
Connect a hand vacuum pump to the vacuum tank.
Apply 15-20 inches of vacuum to the vacuum tank.
Does the vacuum reading hold steady?
--
Go to Step 9
Go to Step 10
9
Replace the vacuum tank check valve.
Is the repair complete?
--
Go to Step 20
--
10
Replace the vacuum tank. Refer to Vacuum Tank Replacement .
Is the repair complete?
--
Go to Step 20
--
11
Remove the I/P accessory trim plate. Refer to Trim Plate Replacement - Instrument Panel (I/P) Accessory in Instrument Panel, Gauges and Console.
Remove the I/P upper trim pad. Refer to Trim Pad Replacement - Instrument Panel (I/P) Upper in Instrument Panel, Gauges and Console.
Remove the HVAC control head. Refer to Control Assembly Replacement .
Plug one of the two HVAC control head ends of the violet vacuum line and install a vacuum gauge to the other.
Connect a hand vacuum pump to the underdash end of the violet vacuum line.
Apply 15-20 inches of vacuum to the vacuum line.
Measure the amount of vacuum on the vacuum gauge.
Switch the connection of the vacuum gauge and the plug between the two HVAC control head ends of the violet vacuum line.
Apply 15-20 inches of vacuum to the vacuum line.
Measure the amount of vacuum on the vacuum gauge.
Is the vacuum reading the same as the amount of vacuum applied and does the vacuum reading hold steady?
--
Go to Step 13
Go to Step 12
12
Repair the leak or restriction in the HVAC module violet vacuum (source) line.
Is the repair complete?
--
Go to Step 20
--
13
Connect a hand vacuum pump to each of the remaining vacuum lines, one at a time, at the connector which attaches to the HVAC control head.
Apply 15-20 inches of vacuum to each vacuum line.
Observe the operation of the vacuum actuator and the related valve(s) to which the vacuum line is attached.
Does each vacuum line, actuator and related valve(s) hold vacuum and operate properly?
--
Go to Step 19
Go to Step 14
14
Disconnect the vacuum line(s) from the vacuum actuator(s) which did not operate properly.
Connect a hand vacuum pump to the vacuum actuator.
Apply 15-20 inches of vacuum to the vacuum actuator.
Observe the operation of the vacuum actuator and the related valve(s).
Does the vacuum actuator hold vacuum?
--
Go to Step 16
Go to Step 15
15
Replace the faulty vacuum actuator.
For mode valve vacuum actuator replacement, refer to Mode Actuator Replacement .
For defroster valve vacuum actuator replacement, refer to Defroster Actuator Replacement .
For air inlet valve vacuum actuator replacement, refer to Air Inlet Actuator Replacement .
Is the repair complete?
--
Go to Step 20
--
16
Is a binding condition evident, not allowing proper actuation of the related valve(s)?
--
Go to Step 17
Go to Step 18
17
Repair the binding condition.
Is the repair complete?
--
Go to Step 20
--
18
Repair the leak or restriction in the affected vacuum line.
Is the repair complete?
--
Go to Step 20
--
19
Replace the HVAC control head. Refer to Control Assembly Replacement .
Is the repair complete?
--
Go to Step 20
--
20
Install components or connectors which were removed or disconnected.
Is the action complete?
--
Go to HVAC System Check
+++++++++++++++++++++++++++++++++++++
Mode Actuator Replacement
Removal Procedure
Remove the I/P upper trim pad. Refer to Trim Pad Replacement - Instrument Panel (I/P) Upper in Instrument Panel, Gauges and Console.
Remove the instrument panel cluster (IPC) to steering column bracket retaining screws.
Reposition the IPC to better access the inside air temperature sensor duct.
Remove the driver knee bolster bracket. Refer to Bracket Replacement - Knee Bolster in Instrument Panel, Gauges and Console.
Remove the ignition switch lock cylinder electrical connector from the retaining tab on the side of the ignition switch.
Disconnect the lock cylinder electrical connector.
Important
Take note of how the ignition switch lock cylinder wire is wrapped around the base of the ignition switch bezel.
Remove the ignition switch bezel. Carefully pull to unsnap.
Remove the hazard warning switch wiring harness from the ignition switch retainer.
Remove the ignition switch retaining bolts.
Reposition the ignition switch downward.
Disconnect both of the vacuum harness connectors from the mode vacuum actuator. Take note of which vacuum hose attaches to which side of the actuator.
Cut and remove the adjustable plastic tie strap (1) from the base of the mode vacuum actuator.
Lift to release the mode vacuum actuator retaining tab and just begin to slide the vacuum actuator toward the steering column bracket.
Rotate the mode valve lever fully forward (counterclockwise) and hold in place until instructed.
Carefully rotate the vacuum actuator toward the front of the vehicle until the actuator is released from the mounting pins on the HVAC module case.
Extend the vacuum actuator below the HVAC module case mounting pins, then slide the vacuum actuator rearward in vehicle, past the pins.
Position the pod of the vacuum actuator between the steering column bracket and the ignition switch housing bracket.
Disconnect the vacuum actuator pushrod from the mode valve lever and remove the vacuum actuator.
Release the mode valve lever.
Installation Procedure
Fully extend the mode vacuum actuator pushrod.
Rotate the mode valve lever fully forward (counterclockwise) and hold in place until instructed.
Connect the mode vacuum actuator pushrod to the mode valve lever.
Position the pod of the mode vacuum actuator between the steering column bracket and the ignition switch housing bracket.
With the vacuum actuator below the HVAC module case mounting pins, slide the vacuum actuator forward in vehicle, past the pins.
Carefully rotate the vacuum actuator toward the rear of the vehicle until the actuator slots engage onto the mounting pins on the HVAC module case.
Check that the vacuum actuator pushrod is not binding on the mode valve lever.
Push the vacuum actuator toward the HVAC module case to secure the retaining tab.
Release the mode valve lever.
Install a new adjustable plastic tie strap (1) to the base of the mode vacuum actuator. After the strap is secure, cut off any excess length.
Connect both of the vacuum harness connectors to the mode vacuum actuator. The brown vacuum hose connects to the upper side of the actuator, the blue vacuum hose connects to the lower side of the actuator.
Position the ignition switch to the ignition switch housing bracket.
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 ignition switch retaining bolts. Tighten
Tighten the ignition switch retaining bolts to 5.5 N·m (49 lb in).
Install the hazard warning switch wiring harness to the ignition switch retainer.
Install the ignition switch bezel to the switch.
Wrap the ignition switch lock cylinder wire around the base of the ignition switch bezel, as noted during removal.
Align the bezel slots to the lock cylinder pins, then push to secure.
Connect the lock cylinder electrical connector.
Install the lock cylinder electrical connector to the retaining tab on the side of the ignition switch.
Install the driver knee bolster bracket. Refer to Bracket Replacement - Knee Bolster in Instrument Panel, Gauges and Console.
Install the instrument panel cluster (IPC) into position.
Install the IPC to steering column bracket retaining screws. Tighten
Tighten the IPC to steering column bracket retaining screws to 3.5 N·m (31 lb in).
Install the I/P upper trim pad. Refer to Trim Pad Replacement - Instrument Panel (I/P) Upper in Instrument Panel, Gauges and Console.
Last edited by bestvettever; Aug 10, 2008 at 11:23 PM.
Thread Starter
Racer
Joined: Nov 2005
Posts: 374
Likes: 0
From: Corona CA - "An Armed Society is a Polite Scociety"
I have the duel zone type A/C but part of my problem is identifying the componants that are listed.
I pulled the valve covers off so if I could find a hose coming out of the back of the intake. You're right, I would have to pull off the maifold so I pulled the battery out to check the hose there. All I was able to locate were wiring harnesses.
Anyone have pics?
I pulled the valve covers off so if I could find a hose coming out of the back of the intake. You're right, I would have to pull off the maifold so I pulled the battery out to check the hose there. All I was able to locate were wiring harnesses.
Anyone have pics?
Last edited by c5Cruiser; Aug 11, 2008 at 10:49 AM. Reason: misspell
Thread Starter
Racer
Joined: Nov 2005
Posts: 374
Likes: 0
From: Corona CA - "An Armed Society is a Polite Scociety"
I found the post! 
http://forums.corvetteforum.com/show....php?t=1966898
And I thought it was going to be an easy trace and fix and I was going to be able to play today.
Crap!
http://forums.corvetteforum.com/show....php?t=1966898
And I thought it was going to be an easy trace and fix and I was going to be able to play today.
Crap!
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Thread Starter
Racer
Joined: Nov 2005
Posts: 374
Likes: 0
From: Corona CA - "An Armed Society is a Polite Scociety"
Well I went from easiest to hardest in hopes that it wouldn't be too hard to fix.
I removed the battery and checked for corrotion and found none. I then went and pulled tha pannel on the passenger floorboard thinking a hose came loose and everything was just fine. I lifted the car and pulled the pannel behind the right front wheel and found the hoses in tact. I found the hose that goes back to the intake manifold, blew air into using a compressor and found the problem. I could feel air coming out of the back of the intake manifold area.
Looks like a job for another day.
So now I'm just going to adjust the parking brakes and call it a day.
Thanks everyone for the help.
I removed the battery and checked for corrotion and found none. I then went and pulled tha pannel on the passenger floorboard thinking a hose came loose and everything was just fine. I lifted the car and pulled the pannel behind the right front wheel and found the hoses in tact. I found the hose that goes back to the intake manifold, blew air into using a compressor and found the problem. I could feel air coming out of the back of the intake manifold area.
Looks like a job for another day.
So now I'm just going to adjust the parking brakes and call it a day.
Thanks everyone for the help.