cruise control
08-18-2006, 12:23 AM
#1
Racer
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St. Jude Donor '06
cruise control
on about every c4 I looked at.it was the same story. CRUISE CONTROL DOESN'T WORK. OR ,REALLY? IT WAS THIS MORNING? OH YEA, mine doesn't either. was this a bad design or did i just pick out EVERY CAR IN THE VALLEY that had a problem with the cruise? do they burn out after a day of 135+-or so mph?
or whats the deal? is it a hard fix or is it not worth the trouble. i only question because i am on the freeway alot.
or whats the deal? is it a hard fix or is it not worth the trouble. i only question because i am on the freeway alot.
08-18-2006, 01:13 AM
#3
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I dont think mine does. Last time I tried the car just slowed down as if I took my foot off the gas (which I did haha). I put on the resume accel and the car acceled quite hard. I dont think it stuck. Just did it as long as I had the switched pushed to the resume accel. Course this was a long time ago and I was driving so I wasnt paying full attention to it.
08-18-2006, 02:20 AM
#4
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My set button does not work but I can set it with the resume accel switch so it is a low priority for me right now. I also have a very hard time turning the brights on and off so I have more work in there than hust this switch.
08-18-2006, 07:12 AM
#6
Le Mans Master
I just fixed my cruise today. I used this article from Corvette Fever as well as the GM Shop Manual.
Cruise Control Diagnostic
In addition:
Check CRUISE, LCD, AND CLUSTER fuses.
Check that your cruise lever is pluged in under the hush panel.
Check all cruise vacuum lines under the hood for holes, obstructions, and proper routing. Unplug sections of vaccum line at a time. Plug one end, and blow air into the other end, to check for leaks. Unplug the end and blow air to check for obstructions.
Check the operation of the small plastic check valve that is behind the plenum, by the base of the distributor. It should allow air to be blown into the intake, but not out. An exact replacement is available at Kragen for less than $1.00
Check the adjustment of the vacuum release switch mounted near the brake pedal under the hush panel:
This switch is a vacuum vent that is open with the brake pedal depressed, and closed with the pedal released. If it's mis-adjusted, it could be venting all the time, not allowing the cruise to hold vacuum. To test it, remove the larger of the two vacuum lines from the bottom of the cruise servo. Try to blow air into the vacuum line. You should not be able to blow air into it with the brake pedal released, and should be able to blow air into it when someone presses the brake pedal. If this is not happening, get under the hush panel, and slide the switch either back or forth one click at a time and do it again, until it's adjusted properly. It's the switch with the vacuum line going to it. On my '86, the switch is adjusted propertly with the switch slid all the way foward againts the brake pedal. This also puts the TCC in correct adjustement, as it's both a TCC switch and cruise vaccum release switch in one.
The other switch you see down there is the cruise electrical release. This does the same thing, but electrically instead of by vacuum, in case one or the other fails you can still stop the cruise. It's open with the brake pedal depressed on automatic transmissions, or clutch pedal on a manual. On my '86 automatic, if the rear brake lights are adjusted properly to light up when the brakes are tapped, the cruise electrical release is also properly adjusted. This is because on an automatic, the brake light switch/cruise electrical release is two switches in one.
Here's the cruise vacuum routing:
Cruise Servo Resistance Test:
First do the finger vacuum test mentioned in the Corvette Fever article with the servo's back cover removed.
You need a Digital Multi-Meter as you will be checking resistance at the servo.
1. Unplug the wire harness at the servo. The metal terminals on the servo are lettered A-E on the connector, left to right. You are measuring at the metal terminals on the Servo itself, not the connector.
2. Measure between terminals E and C: Should be 30-50 Ohms.
3. Measure between terminals A and C: Should be 30-50 Ohms.
4. Measure between terminals B and D: Should be 15-30 Ohms.
If any of the 3 measurements registers no reading what so ever on the Multi-Meter, there is an internal break in the circuit inside the Servo. Replace it.
If the measurements are correct, and the finger vacuum test passes, the Servo is fine. (Note that for the finger test in the article, the larger vacuum line must be plugged in and vacuum switch properly adjusted, or it's port on the servo capped off.)
Cruise Control Diagnostic
In addition:
Check CRUISE, LCD, AND CLUSTER fuses.
Check that your cruise lever is pluged in under the hush panel.
Check all cruise vacuum lines under the hood for holes, obstructions, and proper routing. Unplug sections of vaccum line at a time. Plug one end, and blow air into the other end, to check for leaks. Unplug the end and blow air to check for obstructions.
Check the operation of the small plastic check valve that is behind the plenum, by the base of the distributor. It should allow air to be blown into the intake, but not out. An exact replacement is available at Kragen for less than $1.00
Check the adjustment of the vacuum release switch mounted near the brake pedal under the hush panel:
This switch is a vacuum vent that is open with the brake pedal depressed, and closed with the pedal released. If it's mis-adjusted, it could be venting all the time, not allowing the cruise to hold vacuum. To test it, remove the larger of the two vacuum lines from the bottom of the cruise servo. Try to blow air into the vacuum line. You should not be able to blow air into it with the brake pedal released, and should be able to blow air into it when someone presses the brake pedal. If this is not happening, get under the hush panel, and slide the switch either back or forth one click at a time and do it again, until it's adjusted properly. It's the switch with the vacuum line going to it. On my '86, the switch is adjusted propertly with the switch slid all the way foward againts the brake pedal. This also puts the TCC in correct adjustement, as it's both a TCC switch and cruise vaccum release switch in one.
The other switch you see down there is the cruise electrical release. This does the same thing, but electrically instead of by vacuum, in case one or the other fails you can still stop the cruise. It's open with the brake pedal depressed on automatic transmissions, or clutch pedal on a manual. On my '86 automatic, if the rear brake lights are adjusted properly to light up when the brakes are tapped, the cruise electrical release is also properly adjusted. This is because on an automatic, the brake light switch/cruise electrical release is two switches in one.
Here's the cruise vacuum routing:
Cruise Servo Resistance Test:
First do the finger vacuum test mentioned in the Corvette Fever article with the servo's back cover removed.
You need a Digital Multi-Meter as you will be checking resistance at the servo.
1. Unplug the wire harness at the servo. The metal terminals on the servo are lettered A-E on the connector, left to right. You are measuring at the metal terminals on the Servo itself, not the connector.
2. Measure between terminals E and C: Should be 30-50 Ohms.
3. Measure between terminals A and C: Should be 30-50 Ohms.
4. Measure between terminals B and D: Should be 15-30 Ohms.
If any of the 3 measurements registers no reading what so ever on the Multi-Meter, there is an internal break in the circuit inside the Servo. Replace it.
If the measurements are correct, and the finger vacuum test passes, the Servo is fine. (Note that for the finger test in the article, the larger vacuum line must be plugged in and vacuum switch properly adjusted, or it's port on the servo capped off.)
08-18-2006, 09:37 AM
#7
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Good post 86PACER 
Here is a little info from my 86 manual http://members.shaw.ca/agent86/Cruise%20Control.pdf
Here is a little info from my 86 manual http://members.shaw.ca/agent86/Cruise%20Control.pdf
10-13-2006, 11:44 PM
#9
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cruise
Mine did not work until I found out I was missing the Vaccum reservoir in the engine bay! Replaced it and it worked fine.... make sure you have enough vaccum to control the servo.
10-14-2006, 02:10 AM
#10
Pro
On a 93 its this check valve that usually fails (under fuel rail)... The straight one is for the Cruise Control, the 90 degree bend one goes to the climate control.
This check valve is the most common problem for a 93 cruise control.
This check valve is the most common problem for a 93 cruise control.
10-14-2006, 04:55 PM
#12
The switch that attaches to the brake pedal can wear out. I replaced mine. $15. from the dealer. It takes about 10 minutes. The switch is threaded and the nylon threads seem to wear over time preventing the switch from being held snugly by the holder. I would check there first.
10-14-2006, 05:10 PM
#13
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The cruise wasn't working in my '94. Started checking and found that the vacuum line that runs from servo to the vacuum release valve on the brake pedal was cracked. Standard vacuum line about 24 inches long. Problem replacing is it goes thru the firewall and ataches to the vacuum release servo above the brake pedal. Finally got the new host thry the firewall and had to cut the line by the valve and put a connecter inline as I could not get the old line off of the release valve. Works great now.
One thing I did notice which unfortunately is not there is a indicator on the dash that shows when the cruise is active. If there is an indicator mine does not activate.
One thing I did notice which unfortunately is not there is a indicator on the dash that shows when the cruise is active. If there is an indicator mine does not activate.
10-15-2006, 03:31 PM
#14
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Originally Posted by 03blackburb
One thing I did notice which unfortunately is not there is a indicator on the dash that shows when the cruise is active. If there is an indicator mine does not activate.
No light on mine, you just have to know what position the on/off switch is in sense it is not a momentary like other cars have.
10-15-2006, 04:45 PM
#15
Le Mans Master
Originally Posted by 93*Corvette
On a 93 its this check valve that usually fails (under fuel rail)... The straight one is for the Cruise Control, the 90 degree bend one goes to the climate control.
This check valve is the most common problem for a 93 cruise control.
This check valve is the most common problem for a 93 cruise control.
That's what mine was. $6 fix but saved me a couple hundred when I bought the car, told the guy it was going to cost a lot to fix the cruise and AC so I got a price break
An easy way to know if it is this piece is if you also have electronic climate control and the AC only comes out the defroster/floor vents.
10-15-2006, 07:34 PM
#16
Le Mans Master
10-16-2006, 01:03 PM
#17
Le Mans Master
Originally Posted by 03blackburb
The cruise wasn't working in my '94. Started checking and found that the vacuum line that runs from servo to the vacuum release valve on the brake pedal was cracked. Standard vacuum line about 24 inches long. Problem replacing is it goes thru the firewall and ataches to the vacuum release servo above the brake pedal. Finally got the new host thry the firewall and had to cut the line by the valve and put a connecter inline as I could not get the old line off of the release valve. Works great now.
One thing I did notice which unfortunately is not there is a indicator on the dash that shows when the cruise is active. If there is an indicator mine does not activate.
One thing I did notice which unfortunately is not there is a indicator on the dash that shows when the cruise is active. If there is an indicator mine does not activate.
I was not going to GM for a special piece of vacuum hose.
Also; When my check valve cracked, my A/C vents were having a problem but my cruse worked OK.
Last edited by pcolt94; 10-16-2006 at 01:06 PM.
10-17-2006, 02:39 AM
#20
Le Mans Master
That was great information, thanks.
I believe I found my problem.
Altough all the resistance readings were within the specs posted, when I did the manual check by depressing the servo, then placing my finger over the dump hose bib, the servo wouldn't hold.
I went to O'Reilly's today to buy a new one, but O'Reilly doesn't have them. I did get the AC Delco part number though, so it shouldn't be too hard finding one off a wrecked car.
So I'll try a different servo. I'm willing to bet our cruise servos are used on other makes/models and aren't specific to Vettes, much like MAFs.
I'll post how it turns out.
Jake
I believe I found my problem.
Altough all the resistance readings were within the specs posted, when I did the manual check by depressing the servo, then placing my finger over the dump hose bib, the servo wouldn't hold.
I went to O'Reilly's today to buy a new one, but O'Reilly doesn't have them. I did get the AC Delco part number though, so it shouldn't be too hard finding one off a wrecked car.
So I'll try a different servo. I'm willing to bet our cruise servos are used on other makes/models and aren't specific to Vettes, much like MAFs.
I'll post how it turns out.
Jake