cruise control

[burkey05]

hi,
wondering if someone can help with my cruise control?

i have a '88 gmc swb sierra sle and the cruise control doesnt work(i'm in australia so its RHD)

ive looked under the dash trying to make sure there are no loose/not connected wires or anything, and there are. thankfully some of them are labelled. one is labelled Vehicle speed sensor buffer(i think its coming from the cruise control module), and the other comes from the brake sensor adjustment switch. it has two wires coming from it and one isn't connected to anything.

winaldl shows no fault codes, and none of the warning lights on the dash come on while driving. everything else works as it should, e.g speedo

any help would be appreciated

thx

[ChevyTech]

Take a look at this thread. It should help you do some testing.

http://67-72chevytrucks.com/vboard/s...d.php?t=532924

[burkey05]

thx for the link, i will do some testing

just wanted to make sure tho that this is the brake light switch thats talked about in that thread?

[burkey05]

and that this is the cruise control connection that i should be testing(from the turn signal/cruise/wiper stalk on the steering column)?

the connection in the background illuminated by the light?

p.s those are the non-connected wires i was talking about;

1.anti-lock brake suburban only(not worried about that one, mines not a suburban)
2.vehicle speed sensor buffer(im hoping this isnt a problem
3.daytime running lights(not worried about this one either)

again thx

[ChevyTech]

The brake switch you posted a photo of is not the switch I was referring to, but the wire colors should lead you to the correct circuit.
I can't tell what connector you are shining a light on, but the cruise connector is very small.

My understanding is, all 1988 C 1500 trucks were built with anti lock brakes (RWAL).

I would not trust the labels that someone else put on it.

Do this testing from the thread in the link. We will decide from the results what to test next.

I found an 1988 schematic in one of my old training manuals from the GM training center in Minneapolis. Here is what it shows.

Pink = Power from Ign
Brown = from brake switch/ clutch switch
Gray = Power when cruise switch on
Dark blue = Set switch
Dark green = Resume/accel
brown w/ white stripe = speed signal input
black w/ white stripe = Ground

I will see if I can find some good photos and will post links to them if I find some.

[ChevyTech]

Cruise control switch connector

http://www.google.com/imgres?q=Gm+Cr...o8IH4Bw&zoom=1

[ChevyTech]

I have been having internet connections problems today and gave up on doing serches for this because the connection keeps dropping me.

The switch you posted photo of looks more like a clutch switch for the cruise control.

Are you working on a manual transmission truck?

Here is what the brake switch should look like.

From this thread:
http://67-72chevytrucks.com/vboard/s...ght=Brake+pull

[burkey05]

That's definitely the same cruise control connector, so that's a start. And mine is an auto, 700R4. Does the brake switch have a button that the arm of the brake pedal pushes into when in the normal position? I'll try to take a better photo over the w/end. Don't forget mine is a RHD converted truck, so some of the parts etc might not b as they should.
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[burkey05]

just had a look at rockauto and ive def got the clutch pedal switch mounted to my brake lever..................

[ChevyTech]

That is a clutch switch.

Do your brake lights work?

[burkey05]

funnily enough that part is listed as

clutch pedal position switch for MT(non pivoting)
http://www.rockauto.com/catalog/x,ca...parttype,16665

and

cruise control switch for MT and AT
http://www.rockauto.com/catalog/x,ca...,parttype,4320

[ChevyTech]

Does the brake switch have a button that the arm of the brake pedal pushes into when in the normal position?

Every 1/2 ton 1988 I have ever worked on had the switch like I posted a photo of.

The 1988 heavier duty R/V (square body) trucks do not use the switch I posted a photo of.

I have never worked on a right hand drive vehicle.

[burkey05]

brake lights do work

[ChevyTech]

Originally Posted by burkey05

funnily enough that part is listed as

clutch pedal position switch for MT(non pivoting)
http://www.rockauto.com/catalog/x,ca...parttype,16665

and

cruise control switch for MT and AT
http://www.rockauto.com/catalog/x,ca...,parttype,4320

I don't have a vehicle to look at but I am going to go look at an illustration manual for a auto transmission and see what it shows.

[burkey05]

just wanted to say ChevyTech, that no matter whether i get this working or not, that i appreciate your time and effort.

[ChevyTech]

I found information showing it both with a switch like the clutch switch used on the brake pedal arm of an automatic transmission truck, and I found information showing it is not used on a automatic. I don't have an old truck like that to look at.

Edit: I found a statement in a GM manual stating there is a redundant cruise control switch on the brake pedal. This means two switches on the brake pedal for the cruise. Either switch could stop the cruise from working. The one the usually fails is the switch I posted a photo of.

Do a test to see if the circuits are working.

Unplug the wire connector from the cruise module on the cruise unit under the hood.
Check for power on the Pink wire with black stripe (with the key on) – there should be power.
Check for power on the Gray wire (with the key on and cruise switch on) – there should be power.
Check for power on the Brown wire (not touching the brake pedal) – there should be NO power.
Check for power on the Brown wire (while the brake pedal is pushed) – there should be power.

Give me the results of these tests.

[burkey05]

did the testing results as follows.
just a question, cruise on is the middle position on the turn signal stalk?

Do a test to see if the circuits are working.

Unplug the wire connector from the cruise module on the cruise unit under the hood.
Check for power on the Pink wire with black stripe (with the key on) – there should be power. - there is power
Check for power on the Gray wire (with the key on and cruise switch on) – there should be power. - there is no power
Check for power on the Brown wire (not touching the brake pedal) – there should be NO power. - there is no power
Check for power on the Brown wire (while the brake pedal is pushed) – there should be power - there is no power

[ChevyTech]

just a question, cruise on is the middle position on the turn signal stalk?

Yes


By the test results you got it looks like the switch on the column is bad.

The power for the brake switch for the cruise control comes from the column switch.

Make sure there is power getting to the cruise switch on the pink wire with a black stripe. (key on)

Turn the switch on (with the key on) and see if there is power on the Gray wire coming out of the switch.

[burkey05]

ChevyTech,

excuse my ignorance...

do u mean test near the turn signal stalk(e.g strip back the black sleeve and test the wires within)

or near the cruise control connection under the dash?

[ChevyTech]

Check it at the connector in the bottom photo.

If I remember correctly, the truck in the post I gave the link to had the wire broken in the column where the wire bends from the tilt and not up by the top.

[burkey05]

ChevyTech,

Make sure there is power getting to the cruise switch on the pink wire with a black stripe. (key on)

- power

Turn the switch on (with the key on) and see if there is power on the Gray wire coming out of the switch.

- no power

[ChevyTech]

The results show a bad cruise switch.

Look in the first thread I posted a link to to see the difference in prices for the switch and where the other guy bought his switch.

[burkey05]

ChevyTech,

yup, i figured as much, reading the other thread.

new turn signal/cruise control switch already ordered(see the link)

http://www.ebay.com.au/itm/fits-FIRE...item5d31d994f0

also i was digging around under the dash abit more(its very hard to see under there), and i found the brake light switch that we were talking about earlier.
so i t appears i have both the clutch switch and the brake light switch.

[ChevyTech]

That switch in the top photo is a high failure part. If you ever have brake light or RWAL problems, be suspicious of that switch.

Lets us know how it goes when you get the new parts.

[burkey05]

ok, thanks for all your help so far ChevyTech.

i'll post up results once i get the part.

its got me intrigued now why i have both the clutch switch and the brake light switch!! i might do a bit of testing etc over the w/end to see exactly what function the clutch switch is providing. i can see that the one wire goes from the clutch switch to the brake light switch, and then from there to the cruise control module........................