Did you test it with the rear cover removed like this before you ordered that new servo?




If you do it with the rear cover on and just simply pulled the two hoses off it and cap the port on the bottom, it won't hold pressure even though the servo is good. It needs to be done like pictured for an accurate test. If you did test it like this, nevermind. It must be the servo in that case.

 

Thanks again!

I completely missed that.

I wondered why the test procedure was listed as being done with the rear cover "off".

So one or both of the vacuum connection ports is/are NOT where the test should be made; okay, got it.

So with the rear cover removed, where exactly do I place my finger? This photo doesn't show it that clearly; at least to my old age eyes it doesn't.

I was wondering about that particular test procedure because this afternoon, I spent hours in my local wrecking yard trying to find a replacement servo. Every one I found I tested by removing both hoses and placing my fingers over both hose bibs and NONE held the bellows in.

Now I see I was doing it incorrectly.

Jake

 

My cruise control works like a charm I havnt had any problem what so ever with mine

 

The 96 vacuum check valves are different. There are two, each are round, one about the size of a quarter and the other the size of a nickel.


They are located in-line with each other and located under the black plastic cover that shrouds the injectors, etc.

I checked both of mine by blowing/sucking on them and they only allow air passage in one direction: toward the intake manifold.

Jake

 

I removed the back cover on the servo and tried placing my fingers over every hole that I thought could pass vacuum.

I ignored the holes through which the screws pass, but no matter what I did, the bellows would NOT hold.

What am I doing wrong??

I need specifics on what to do.

Jake

 

Can you post a picture of your servo with cover removed? I want to make sure your servo is the same as the earlier ones. Then I can also quote and circle the button you need to press.

 

AHHHH, NOW I SEE. I've got to push the button. Yes, I recall seeing it when I had to cover off, but had no idea it was supposed to be pressed.

Gotta go do that now. I'll let you know.

Jake

 

I really appreciate all the help.

Well, I just tried it and still no good.

The cruise control servos on the 1986 and the 1996 are different.

My 86 has a chain arrangement connected to the cruise control cable. The chain is covered by a rubber accordian like sleeve. The chain is similar to what you find on a ceiling fan.

The 96 has NO CHAIN but, instead, has a flat metal bar with numerous holes drilled in it extending out from the servo.

When I looked closely, I saw that my 96 has only ONE silver (shiny) colored button and I tried pushing it (pretty hard too) but it didn't move and the bellows didn't hold. Yes, I had to cover off too.

I tried it with both vacuum hoses removed and blocked,

then I tried it with larger vacuum hose still attached but the smaller one removed and blocked,

then I tried it with the smaller vacuum hose attached but the larger hose removed and blocked,

In each case, the bellows wouldn't remain retracted.

The plastic servo cover has two numbers stamped on the outside and one on the inside.

The outside numbers are: 25110835 and 2929501A

The inside number is: 25110772

I hope I did the checking procedure the right way this time.

Does it look like new servo time for me?

Jake

 

My serve doesn't look like the one in the photo. No rubber covering and no chain. It has a metal bar with holes in it.

Jake

 

1996 LT1/Auto Trans.

Yesterday I went to my local wrecking yard, removed and checked about a dozen cruise control servos. I only found one with a button that would depress and hold the bellows in. So I bought it for five bucks.

Installed it and still the cruise doesn't work.

I checked the resistance on both servos - the one originally on the car and the one I bought for $5. Both checked out with ohm readings within spec.

I've done the brake pedal dump switch check and checked all the vacuum hoses for leaks. I also checked the two vacuum check valves on the passenger side near the intake manifold.

I inserted a vacuum gauge in the cruise hose at the servo and have 16".

Now I need to know what voltages the servo connector should have.

I remember reading that I should be able to hear the click of a relay when the cruise control is turned "on", but I don't.

As soon as I get my Service Manuals I'll be able to look up these kinds of things, but for now I'd appreciate any additional info.

I'd hate to have to take the car to Chevy for the repair. To me that would be a last resort measure.

Thanks,

Jake

 

Here's an Update. 1996 LT1, Auto

As I posted before, I went to a wrecking yard and after searching through a lot of different vehicles (no Vettes were there) I decided to buy the only one I found that would hold the bellows in while pushing on the button.

It came off a 1990 Pontiac Tempest and cost five bucks.

I installed it on my 96 LT1, before I left the yard, but the cruise still didn't work.

So, since my son has a 96 LT1 Vette also AND HIS CRUISE WORKS, I decided to check out the servos on his Vette. I removed his servo and installed MY ORIGINAL SERVO and his cruise CONTINUED TO WORK NORMALLY.

I then pulled over to a parking lot and swapped in the Pontiac servo I bought at the wrecking yard and it ALSO worked normally.

So if you ever need a servo seems it's not necessary to get one off a Vette. Guess this is much the same as MAF sensors, etc.

I did notice that the servos come in two different diameters - the LT1 takes servos with the larger diameter bellows.

Bottom line is I still haven't solved MY cruise control issue, but I bought all new vacuum hoses and plan to install them over the weekend. If I still can't get it work with the new hoses, I believe the problem has to be electrical since I've already eliminated the check valves and fuses as the cause.

I'll post the results.

Jake

 

[QUOTE=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.
QUOTE]



Replaced my valve for under $12 all works great!!

 

That's the one I had to replace for my climate control - the heat will make it brittle as heck - fell apart when I touched it. The good news is it only cost $6.50 from the stealership. One of the few inexpensive parts on a corvette.

 

You can get the exact same check valve at Kragen for .75 cents.

 

[QUOTE=biggrizzly]The 96 LT1 doesn't have the bent one; only two round ones. One about the size of a quarter and the other a nickle. Both are under the fuel rail cover.

Both my 96 LT1 and my son's have the exact same check valves; blue and white in color, inline with each other on the same vacuum hose.

Jake

 

1996 LT1, Auto trans.

Well, just came in from removing the cruise control vacuum switch on the brake pedal. The switch passed the "blow through/suck through the hose" test.

I did notice the switch has a two pin male electrical connector on it BUT NO FEMALE CONNECTIOR was present. I couldn't find any electrical connector that was un-plugged and dangling from the mass of wires under the dash either.
So what I have is a cruise control vacuum switch with a tight fitting vacuum hose attached AND which also has a two male pin electrical connector BUT nothing plugged into it and NO dangling connector.

The brake light switch has TWO plug in connections; brake lights work fine.

What's up with that two pin male connector with no plug in?

So far I've checked both check valves, vacuum reading at the servo, resistance on the servo electrical connection male pins, vacuum hoses for cracks/breaks/tight connections and THREE different servos on a working cruise in my son's Vette (all worked).

Where do I go from here??? Any help will be GREATLY appreciated.

Thanks,

Jake

 

Check it and make sure that it is firmly seated. Just push it. This is a common problem with people who have replaced their brake booster.

 

Can you post a picture of yours? I'm kind-of curious what a 96's looks like....Thanks....

 

I just recently bought a new digital camera but haven't had time to use it yet. I'll see if I can get some shots of the check valves today, assuming I can figure out how this sucka works.

Jake

 

Here are the links to the photos of the brake switch, etc.

http://i140.photobucket.com/albums/r...6/000_0002.jpg
http://i140.photobucket.com/albums/r...6/000_0005.jpg
http://i140.photobucket.com/albums/r...6/000_0008.jpg
http://i140.photobucket.com/albums/r...6/000_0006.jpg

I still have to figure out how to post the actual photos.

Jake