1990 Chevy truck breaks ? - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Electrical
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 07-01-2005, 03:17 PM
Member
 
Last photo:
Join Date: Apr 2005
Location: Sherman, Texas
Age: 34
Posts: 55
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
1990 Chevy truck breaks ?

I've taken out the computer in my truck and I 've got just about got everything to work. The biggest problem I'm having is the brake lights. The running lights and blinkers work. I've scanned the diagram for you all to see. I've found that the purple wire coming for my switch isn't hooked up I cut it. I'm thinking that it may have went to the computer. Any Idea's on a quick fix?


    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 07-01-2005, 05:25 PM
1931 steve's Avatar
Hotrodders.com Moderator
 
Last wiki edit: How to rebuild an engine Last photo:
Join Date: Nov 2004
Location: Michigan
Age: 43
Posts: 1,207
Wiki Edits: 4

Thanks: 0
Thanked 0 Times in 0 Posts
You say that the parking lights and running lights work, just not the brake lights, right? If this is true, is the way you are checking just by seeing if the brake light bulb lights or are you using a test light at the harness connector? If just the bulb check is the way you are check with a test light. These trucks have a lot of problems with the rear light(s) boards. It is possible that both have failed. Also you wire diagram looks like it is for 1996 and later models.

Steve
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 07-01-2005, 07:26 PM
Member
 
Join Date: May 2005
Location: hardin, ky
Age: 27
Posts: 37
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Quote:
Originally Posted by 1931 steve
Also you wire diagram looks like it is for 1996 and later models.

dang, u beat me to it
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 07-01-2005, 08:53 PM
edge's Avatar
Time is short, are you ready?
 
Last photo:
Join Date: Jun 2004
Location: South Carolina
Age: 45
Posts: 658
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
Quote:
Originally Posted by Cameltoe
I've taken out the computer in my truck and I 've got just about got everything to work. The biggest problem I'm having is the brake lights. The running lights and blinkers work. I've scanned the diagram for you all to see. I've found that the purple wire coming for my switch isn't hooked up I cut it. I'm thinking that it may have went to the computer. Any Idea's on a quick fix?
If you have taken the computer out of your truck, I assume you have a carb, no lock-up converter or anti-lock brakes.

Yes, you are correct that the purple wire goes to the computer. 1990 GM truck - This will be similar to my 94' Suburban. You should have a four wire brake/TCC switch under the dash. The pink/blk and purple wires feed the ECM (PCM w/ 4L60E). The pink wire is 12v ignition-on source and goes to the part of the switch that is normally closed. This feeds voltage to the ECM (or PCM) via the purple wire when the brake pedal is not depressed. The ECM (or PCM) uses this signal for TCC (and/or 4L60E) controls, cruise control and anti-lock brakes (if equipped). So, if you press the brake pedal the voltage to the ECM (PCM) is interrupted.

Removing the ECM and not having the purple wire input will not affect the brake lights on a 1990 truck; only TCC, cruise and anti-lock brakes if still functioning. If your brake lights are not working, you need to check the orange and white wires. One of these (I can't remember) is a full-time 12v battery source. It feeds the part of the switch that is normally open. So it only makes the connection when the brake pedal is depressed. I think the orange is the battery side of the switch and the white is the brake light side of the switch. Use a test light to probe and determine which is which.

I had this switch go bad and the section controlling the pink and purple wires was intermittent. I love my cruise control and this problem would randomly turn it off. It became very frequent and I also noticed the TCC lock-up going in and out at cruise. By using my Auto-X-Ray scanner and researching for about two weeks I determined I needed a new switch, which is about $15 at GM.

If your brake lights are not working, check the orange and white wires. Using a test light will easily determine if it is the switch. Don't worry about the purple wire if you are not controlling TCC, cruise and/or anti-lock brakes; but be sure to put some electrical tape or a wire nut on the cut end.

Good luck, Ed www.edgesz28.com


Did You Know?
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 07-02-2005, 10:36 PM
docvette's Avatar
Hotrodders.com Moderator
 
Last wiki edit: Rebuild an alternator Last photo:
Join Date: Mar 2004
Location: Lafayette, california
Age: 62
Posts: 7,362
Wiki Edits: 12

Thanks: 0
Thanked 6 Times in 3 Posts
Brake lights

Doc here,

Go Directly to your Brake light switch..

You should have (Depending on your specifics) a set of contacts for power, a set of contacts for lights, a set of contacts for Cruise control, a set of contacts for Computer..(some of these can be shared contacts)

Isolate the set of contacts that support your brake lamps, Then find the center wiper on that switch for those contacts...Re~fuse, and test for power..My guess here is in grafting the Computer harness, you cut constant power to the brake light system all together..

To test in Bits, just pull the lamp wires off the switch, and heat them up with a fused 12 volt source..the lights should come on...not blow a fuse.

Then still disconnected, heat up the power contacts on the brake light switch the fuse should remain stable, and you should be able to meter 12 volts OUT a set of contacts with the pedal depressed (or even in a bad mood...lol..) Those are the 2 you need to hook up.

Doc
__________________
Aftermarket Solutions
Electronic & Electrical
Innovations
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 07-03-2005, 11:43 AM
Member
 
Last photo:
Join Date: Apr 2005
Location: Sherman, Texas
Age: 34
Posts: 55
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Thanks for your help guys. I went and bought a switch for an 85 chevy pick-up and made a bracket at work to hold it.

Reply With Quote Quick reply to this message

Recent Electrical posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Engine swap Chevy 350 ina a Datsun 521 truck evh5150 Hotrodding Basics 17 09-12-2007 11:58 AM
94 chevy truck runnin' like poo! bluesmanjesse Engine 11 11-09-2006 03:54 PM
Car 235ci into '53 Chevy Truck New2theart Engine 8 10-17-2006 01:37 AM
53 chevy panel truck huligar General Rodding Tech 12 04-27-2006 04:53 AM
1951 Chevy Truck chevblazk5 Suspension - Brakes - Steering 3 01-26-2006 09:27 PM


All times are GMT -6. The time now is 11:37 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.