1990 brake light switch

[57 3100]

guys, i see the brake light switch in my 1990 k-1500 with auto trans, is way up in there. how hard is it to replace ? any special tools ? i dont think my year is held in with a metal clip ?
my cruise control has stopped working and i seem to have the correct power from the cruise control switch, and was told it could be a faulty brake light switch, so i want to try it.
thanks

[ChevyTech]

For C/K trucks 1988 to 1993

Brake Switch mounting – Installing:
The body of the brake switch should not move with the pedal at all.
When you have the switch removed look at the side of the switch that would be towards the parking brake pedal if the switch were still installed. There is a protrusion on the switch that must slide into an opening where the switch mounts. Somewhat like a big square lug into a slot. If not installed with the Lug inside the grove it belongs in the switch will move and not stay in adjustment.

Brake Switch adjustment
Here is how the switch is adjusted:
On the curved side of the switch, which is pointing down and somewhat towards the front of the vehicle when installed, the end of a lever protrudes slightly out of a slot.
While holding the brake pedal down a little ways, slide the lever that protrudes from the slot toward the driver’s seat.
Let go of the lever, then return the brake pedal to its fully released position, and the switch should self adjust.

[57 3100]

thanks so much for the info ChevyTech. i hope to replace the switch this afternoon after work.. i will let you know how it goes, and if it fixed my cruise control problem. thanks again.

[3strats]

Ahh Haa! I too am having the same problem.(i think). If i'm thinking correctly the brake switch has something to do with the trans locking up as well? Cruize doesnt work and trans will not lock up until i put my left foot under brake pedal and pull up towards steering wheel. Works fine after that. Am i crazy?

[3strats]

Sorry. I always forget. 1990 model c1500. 5.7ltr. TBI. 700R?. Black. Whiskey dents on doors(PO).

[ChevyTech]

Originally Posted by 3strats

Ahh Haa! I too am having the same problem.(i think). If i'm thinking correctly the brake switch has something to do with the trans locking up as well? Cruize doesnt work and trans will not lock up until i put my left foot under brake pedal and pull up towards steering wheel. Works fine after that. Am i crazy?

No, you are not crazy.

The adjustment on this style brake switch moves way to easily.

Try just adjusting the switch but if it gets out of adjustment again, you should replace the switch.

[3strats]

Cool. Thanks for the info. Hate to jump into the middle of a thread like that but this site has a ton of useful information. Its good to have guys that are willing to help out as much as they do. Thanks again.

[57 3100]

ok guys, here we go.

i installed my new brake light switch, and let me say, the engineer who designed this style of switch is an absolute fool.( cant say how i actually feel ). it took me 90 minutes to get the old one out and the new one in... what a real pain it was.
got it in and got it adjusted..... but it did NOT fix my cruise control problem.
i need some more help.... here is what i have as of now..

i checked the 4 wires coming from the cruise control switch it seems to me to be good ?
key on=blue wire hot
cruise on=green wire hot
press set/decelerate=brown wire hot
press accelerate=yellow hot.
so, all 4 functions on the switch are working, so my problem should not be the switch, correct ?
someone on another site said his problem was the "electro motor cruise control " box under the hood on drivers side firewall. should i try that next ?
i took the cover off that box and it all looked new inside. checked the 7 wire plug that press fits onto the box, and all i have is one terminal that is hot when the key is turned on, and another terminal that is hot when i press the "set/decelerate" button. i could not get a terminal to go hot when i pressed the accelerate button, and i didnt check to see if one of the terminals would got hot when i pressed the brake pedal. (i just thought about that).
any thoughts on what i should check or try next ?
i might hit the local junk yard tomorrow on ym way home from work to see if they have a control box that i could try out...

thanks for the help guys... i really want my cruise control working again.

[ChevyTech]

The wire colors don't match what I have, put it does sound the the cruise switch in the column is working ok.

and i didnt check to see if one of the terminals would got hot when i pressed the brake pedal. (i just thought about that).

That is the most important thing to check.

someone on another site said his problem was the "electro motor cruise control " box under the hood on drivers side firewall. should i try that next ?

That is a low failure part. It is the least likely to be the problem.

Here are the wire colors for testing at the module for1993. At lest some if not all should match.

1993 Cruise module wire colors:
Pink wire with black stripe = power in from gage fuse
Black with white stripe = Ground
Brown wire = power back from brake switch (and clutch on manual transmission vehicles)
Dark blue wire = Set & coast - signal from cruise switch
Dark green wire = Resume & accelerate - signal from cruise switch
Gray wire = power from cruise switch
White wire = to PCM – (TCM on diesel engines)
Red with white stripe = Vehicle speed signal from DRAC module

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.

[57 3100]

ChevyTech, thanks so much for the help..
it does seem that my 1990 wiring is different than your 1993.
you state there are 8 wires to your module, and on the female wire connector to my cruise control module has 7 wires,
brown w/ white stripe
white
blue
green
black
black w/ white stripe
red

so far all i have is my red wire is hot with key on and my blue wire gets hot when pressing the set/decelerate button. tomorrow after work i will check and see which wire, if any, gets hot when i press the brake pedal down. and i will double check to see if i get any wire hot when turning on the cruise. as of yesterday no terminal got hot when turning on the cruise.

what would not let that happen, if i am getting a hot wire when turning it on at the switch ?

and where is my PCM located ?

i really am not good at electrical stuff, and am surprised i have gotten this far. its driving me crazy and im just about ready to quit. i love my truck and want the cruise to work, but im not going to take it to a mechanic and spend a ton of money getting it going........

went to the junk yard today and there were a couple of trucks with the cruise box on them, but they cut the cable, and i wanted a box complete, so i left empty handed....

thanks again for the help..

[ChevyTech]

...and where is my PCM located ?

Technically A PCM is in a vehicle where the computer does all the shifting of the transmission.

Your truck has an ECM in the area behind the glove box.

If I can find some free time tomorrow, I will see if I have a schematic for a model year earlier then 1993.

[57 3100]

thanks so much ChevyTech... i really appreciate the help... i have looked and looked and cant find ay schematics for my truck....

[ChevyTech]

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

[57 3100]

thanks so much chevytech...
i will put the test light on the terminals when i get off work today.

all mine match up except whet i thought was black must actually be brown, and what i thought was white must be gray.

i will report back later this afternoon.

again, thanks a ton

[57 3100]

chevytech..... here is what i found out today.
unplugged the connector at the cruise control box under the hood..

pink is hot when ignition is on... good.
dark blue is hot when pressing the set/decelerate button....good
black with white stripe is ground.....good

i could not get the gray wire to light up when turning on the cruise switch
not sure how to check the brown with white stripe wire, speed signal input.
and when pressing on the brake pedal i am not getting hot on the brown wire.

so i have 3 of the 7 working.
its hard for me to understand what could be wrong when all functions are good coming right out of the cruise switch/blinker arm, and its not reaching the cruise box under the hood ? well, actually i am not getting the terminal to light up when pressing the brake pedal, and nothing when pressing the resume/accelerate button.
what could be interfering with it somewhere from the switch to the box under the hood ?
i double checked all fuses and every one is good....
i think i have hit a wall, at least with my experience...

got any one last tests i could try ?

thanks again man..

[ChevyTech]

You need to look closely at the terminals in the connectors to see if they are damaged or stretched out so they are not making connection.

The cruise has its own little harness going through the firewall so it does not go through the bulkhead connector or any thing else.

If it tests good on the inside, and bad on the outside, you need to move your way down the wire until you find the open/break.

The gray wire has a splice where it goes in two directions. One split goes to brake switch and the other goes out to the cruise module on the firewall.

My guess is once you find the problem with one of the wires , the other wires will have a problem in the same place. I would trace down the gray wire.

If you are testing the switch with an ohm meter and not a test light, it may test ok with a meter but can't handle any load and won't test good with the load of a test light.

You have identified a problem and are getting close. Don't give up now.

[57 3100]

hello and thanks again chevytech..

yea, i was trying to see where the wires for the cruise come through the firewall, but man, it is so crowded up there, i really cant see anything under the dash, trying to trace them wires. i will try again tomorrow, i got really frustrated today, and quick, after the mess of the brake light switch yesterday, and the humidity and heat down here in south florida. (im a welder and dont like sweating after i get off work). lol.

and correct me if im wrong..... the wires coming from the cruise control switch are really small gauge, so somewhere in the column they bust attach to a connector and get bigger ? and i couldnt match the color of the small gauge wires from the switch to anything that was coming out of the bottom of the column.... thats when i gave up today.

weather permitting, i will try and see if i can find that gray wire and the entire pack coming in through the firewall, under the dash.... and go from there.

i will report what i find tomorrow...

i cant thank you enough for your input. if it weren't for guys like you, there's a lot of us who would be totally lost.

thanks again.

[57 3100]

oh yea, i am testing everything with a test light...

[ChevyTech]

You’re welcome. A thank you is always appreciated.

If you are testing right by the turn signal lever, that is not where they usually fail. It is common for the wires to break or get pinched where the column tilts, if it is a tilt column.

The cruise switch should connect to a normal looking wire harness for the cruise on the left side of the steering column usually just below where the large mounting bracket that holds the column.

The wire harness should go through the firewall in a round grommet in the area just above the bulkhead connector near the brake booster. Just follow the wires from the module back to the firewall. From the inside of the cab it is above the convenience center ( the black plastic electrical panel).

[57 3100]

oh..... got it..
im checking my wires too close to the cruise switch on the blinker arm....
im betting thats probably where my trouble is going to be, once i do check the wires a little more down the line. sounds logical the wires can break because of the tilt.
i will try and see what i can come up with today, hopefully.
when looking in the past, i cant figure out how that cruise switch/blinker arm even comes off.. do i have to take the steering wheel off, or disassemble the column in some fashion ?
thanks much... with your help, im not giving up just yet.. thanks for the push

[ChevyTech]

Originally Posted by 57 3100

...when looking in the past, i cant figure out how that cruise switch/blinker arm even comes off.. do i have to take the steering wheel off, or disassemble the column in some fashion ?

You just pull it straight out.

[57 3100]

OK chevytech... you got me going int he right direction now man....

i see where the cruise wires come down from the switch and plug into a connector, making the 4 small wires into 4 bigger wires.
and although at the end of the harness from the switch is what looks like only 2 connectors, must be split down the middle making actually 4 connectors.

as stated before, at the switch all 4 wires check out good, but down at the connector i am only getting 2 that are good, pink=key on and blue=set/decelerate, and they are on the same leg.
the other leg, green and grey wire, im assuming should be for cruise on and resume/accelerate ? although you did say the gray wire was for the brake, and i pressed on the brake and could not get anything to light up.
so down at the connector, even though keyed power is working and set/decelerate is also working, since im not at least getting any power when the switch is turned on, im assuming there is a break, probably like you said, at where the column tilts....

i called autozone and they want $139.00 and 3-5 days, and NAPA wants $219.00, same wait. i found a new switch at rockauto for 45 dollars, and i just ordered one. should have it here sometime next week.

and i tried pulling on the switch and it came out of the socket just as you stated...

so, with your help, i am one step closer, and will report back next week when i get the switch in.... i have to remember to attach a feed wire to the end before pulling it out..... or i will be in trouble.

thanks again so much chevytech... could not have gotten this far without your help.

[ChevyTech]

You're welcome!

The Gray wire is power coming out of the switch and splits into two wires to send power to the module and to send power to the brake switch. It sure sounds like the cruise switch is bad.

When you unplug the old switch look at the end and notice there is a small hole through it. I would tie heavy fish line to the end and pull the fish line up the column when removing the old switch. Then tie the fish line to the new switch end and pull it in using the fish line. Fellow techs of mine would do the same thing using mechanics wire but I preferred heavy fish line.

Even if you break the fish line, or down pull in a wire, you can get the new wire down the column because it is stiff enough to work with.

and although at the end of the harness from the switch is what looks like only 2 connectors, must be split down the middle making actually 4 connectors.

Both sides are used with separate circuits. Look closely at the connector. Two contacts on one side and two contacts on the other side equaling four separate circuits.

I didn't realize how expensive the switches are. I have replaced piles of them over the years.

Let me know how it goes.

[57 3100]

thanks for the fishing line tip... im a bass fisherman and didnt even think of that. im sure it will be easier than using a small diameter wire...

yea, at first i was stumped when i took the cruise connector out of the female connector, under the column, actually thinking another male connector was missing, or came unplugged, then i remembered there were 4 wires coming down, looked at the connector and figured it out...

cant wait to get my switch next week, and it will have new white lettering on it, my original is all worn off.

thanks much and i will let you know how it goes next week

[57 3100]

UPDATE !!!! UPDATE !!!! UPDATE !!!!

guys, i was surprised to have my cruise switch delivered this morning from rockauto.com
went outside, installed the new one, went for a test ride, and holy cow, I NOW HAVE MY CRUISE CONTROL BACK !!!!

all the headaches was worth it and i am now happy to have it working once again.

thanks to everyone, but a very special thanks to ChevyTech who kept the info coming and didnt let me give up, thanks a bunch man, i really appreciate it.

after all is said and done, if i would have checked for power at the end of the cruise control switch wires, and not at the beginning, like i was doing all along, i would have found out the wires were broken somewhere in between, probably from the tilting of the steering column, just as ChevyTech had suggested...

i wish there was more input i could actually help out with here on this site, but with guys like ChevyTech around, who needs me. LOL.

thanks again.