Hello all. This is my first post on this forum. I am an owner of an all original 1988 Convertable. I have had my Vette sitting up for about 6 years and have just got it back out on the the street. Here are a couple photo of it.




I have pretty much fixed everything that has not been functional like the radio, antenna, headlight motors, etc but am having problems with trying to resolve an issue with the cruise control. I guess the first couple of questions (and I have picture to show) I have are what these particular items are and what dose the associated hoses go to and do they have anything to do with the cruise control.

First set of pictures





These connectors look like vacuum lines. They are located right next to the distributor on the driver side. One end of the connector is a straight connector and the other end is a 90 degree elbow connector. As seen in the picture, they are not connected.

In the next picture I found these two lines disconnected. One has a small little canister type connection with a funnel shape at one end and the other end leads all the way around to a round ball like vacuums canister behind the driver side parking and turn signal light. The red highlighted line is not connected to anything and leads to the cruise control module or control.



The following picture is the round ball canister behind the parking light.



I never disconnected these lines and I am assuming that a mechanic at some point during repairs in the past disconnected them and either forgot to reconnect them or just overlooked them.

Just an added note. I have been searching around the forum to find an answer and I had noticed in some threads that if the vacuum line for the cruise control is not connected, the Air condition system will blow one level of air flow whether you have it in Max or Bi-level and when I have it in either, air is blowing out of the defroster outlet which I don't think is right.

Anyway, any help or suggestions would be greatly appreciated.

 

A vacuum line connected to the passenger side rear plenum goes to the rear of the plenum on the driver side rear area and connects to a vacuum check valve that looks like this.



The check valve has one input and two output ports.

One output port goes goes into a wiring harness and then the vacuum line comes out of the harness and goes into the interior to the HVAC Programmer to provide vacuum for the vacuum operated actuators to control the air vents.

The other output port goes to a T fitting. At that fitting one line goes to the black plastic vacuum reservoir ball and the other line from the T fitting goes to the cruise control servo motor.

If you look at the cruise control servo motor located above the battery you will see two vacuum hoses. One hose goes to the firewall. The other hose should go to the vacuum T fitting.

 

Good pictures, looks just like my '88, only cleaner. I'm also interested in facts you're concerned with. I'll be watching.

 

Thanks for the quick response. I see the two lines that go from the cruise control above the battery. There is one that does go to the firewall behind the brake booster but the other is the one that is the one that is disconnected and I am assuming that someone left off the T-fitting you are showing. I cannot find it. Also I cannot find the vacuum line that comes from the passenger side plenum to the Driver side plenum. Is it easy to see where it is coming out of or is it buried in a place that is hard to find?

Also the picture in the original post shows a line that has the straight connector and the 90 connector that looks like they should be connected together. That is the line next to the distributor.

This is at the end of the line that goes to the t- fitting and then on to the Ball vacuum canister. How does this fitting play into all this.

 

Thanks. i am the second owner and it has 87k original miles. i am trying to get it all fixed then it will be time to get all te dirt that has been sitting on it for the past 6 year while layed up in the garage.

 

Look on the rear of the plenum on the passenger side there should be I believe two vacuum hose fittings on the side of the plenum. One of the hoses goes to the fuel pressure regulator. The other fitting should have a hose which goes to the driver side to the one way check valve that has two outputs. One output hose from the check valve goes into a wiring harness then to the firewall into the interior.
The second output goes to a T fitting.

If you can't fine the T go to an auto part store in the Help isle and purchase one. Take the hose from the cruise control servo so you can verify what size T fitting you need.

 

I believe I solved the problem. I found another thread that had some pictures of what the hook up points were and found that the 3 way valve that Hooked on Vettes displayed is not the one on my vehicle. This is what I found.



One of the ports had been broken off in the 90 fitting that was next to the distributor and the other end (that straight line fitting next to the distributor that was supposed to be connected to the plenum on the passenger side was just laying on the manifold and the port on the plenum was just capped off with a rubber cap. Now that I think I have found where all the lines lead to, the only thing left to do is to find that 3 port check valve. There was a part number listed in the thread an I will call dealership parts to see if they even carry it anymore. I won't really be able to pass along if that was the actual problem till I get the part. I will keep you all abreast of my findings. Thanks for the great help! Hopefully this does the trick.

 

http://api.viglink.com/api/click?for...e%20Forum&txt=

I tried to show someone this.

 

That is a good diagram. I found this picture and it show it in term even I can understand.
The check valve that Hooked on Vettes showed could also be an option. I am going to go down to the local auto store and see if they have those in stock as well as the OEM part. I hope to have good news tomorrow. If not, I will probably have to order the part and it won't be till next week when I can give it a whirl.

 

You can get the vacuum check valve at any auto parts store for about $4.

For reference, mine is located next to the distributor and looks like this:

 

Well I bought the 3 port check valve and I think it fixed the AC blower problem but the cruise control still does not work. I do not feel any vacuum in the line from the Check valve to the round ball accumulator. If there is any more suggestions on the cruise control issue l'm all ears.
Oh I did find this while routing vacuum lines.

There is another canister right in front of that ball accumulator that looks like a vacuum canister. There are 2 large lines coming out of it that are not connected to anything. I had body work on the front bumper years ago and they had to remove the whole bumper. I am wondering if they for got to hook these lines up. Could not find where they would go.

 

If it is connected to bottom of canister, it connects to nothing, it's a vent

 

Those are fuel return and vapor lines and they need to be connected, I have an 85 so yours is probably different.

Ok follow me here for cruise, from engine vacume to the large end of the one way checkvalve, from the check valves 2 remaining connectors,
one goes to hvack and the other goes across to battery area where another tee (3way) not a checkvalve. The only checkvalve is by the distributoe. Just a flow thru 3 way tee. run one line to the cruise control servo and the other line to the bottom of the vacume holding ball. Keep in mind the large vacume hose to the firewall must be in good condition. This is totally separate from your fuel canister vapor hoses. Check fuses and try it.
Good luck

 

That is exactly how it is connected.

 

This thread shows how the vapor canister is connected (see post #25):

https://www.corvetteforum.com/forums...nk-normal.html

 

Hmmm? Wondering which one is it.

I guess my real question here is if it is a vent line, why is it that the two lines that have nothing connected to them both go to two ports of a 3 way fitting? The third line out of that 3way fitting is the only one that goes to the bottom of the canister. Why even bother with the thre way fitting when there is only one line out of the bottom of the canister. Doesn't make sense.

 

Someone needs to take a pic off 88 vapor line connections, I would but mine may be different, I have 85

 

Hi

This is what i came across with my 85, the cruise control would not set.
The cruise had worked fine however occasionally it would drop out, having to reset and be ok for a while.

It got worse till it would not work at all....

See the image below, check the tcc switch on the brake pedal.
That one is to disable the torque converter lock up, it also disables the cruise control.

I have one switch with the cruise control vacuum and the other is the brake light and tcc switch, found the brake light would close but the tcc was open and did not change with brake depressed.

The small tab broke, of course i cannot drive slow without cruise control so had to fix it asap.

 

I think the pic in the provided thread shows how the canister is hooked up, I was trying to help you get your cruise hooked up.

 

Hmm? That's an idea. Back to crawling under my dash. Let you if that works.