Printer Friendly Forum Posts - Heated Washer Fluid Switch, 07 GMC Sierra

OK, to start it is an 07 GMC sierra extended cab truck with the 5.3L engine. The truck came out with the heated windshield washer fluid option. Then there were some fires and GMC recalled all of them and disabled the heater system. All they really did though was take out the heater, cut the wires, tape the wires, and pull the 60 amp fuse.

Now, what I want to do is to reuse the original heated washer switch for a cargo light switch. I already know which wire I need to supply power to the light. What I cant figure out is the wires going to and from the actual heated washer switch. I do have the switch out, and much to my surprise, there is 10 wires going to it!

I did find out that 2 of them are hot, not sure if I checked with the key on or off though. Does anybody have a diagram of what the wires go to? I also had the switch apart, trying to figure something out, didn't work though! Maybe if I took a picture of the circuit board? Would that help?

Hi,
The switch has many wires because the connector is shared with other optional equipment.
There should be continuity between the black (position 3) and light green (position 7) when the button is pressed.
The yellow (position 4) should have power with the dashlights being on.
A ground on the dark blue/white (position 8) should turn the LED indicator on. Ignition will probably need to be on for the last operation.
The operation of the button will require additional circuitry as the button is meant to switch low current.
Mark

First of all, thank you, thank you, thank you! At least now I have a starting point. As far as the low current, not to worried about that. I am planning on using a low current feed to trigger the BCM, so that shouldn't be a problem. And just to make sure I follow you, it should go like this: power in on black (pos.3), switched power out on light green (pos.7), yellow (pos.4) is power from the dash lights, and dark blue (pos.8) will go to ground for the indicator light. I think (and hope) I can make this work. Thanks again.

The black wire is meant to be ground as it also is the return for the LED backlight. The light green is to supply a ground when the button is pressed (per how the switch is designed). The LED indicator in the switch is independent of the pushbutton and backlight circuits.

So, the switch actually switches the ground on and off? I wonder if I could use a relay to reverse the polarity?

The light green will only have a ground on it as long as the switch is pressed. Yes, a relay could be used to invert the polarity. Are you looking to operate the factory cargo lamp or an additional unit?

Factory light. And the factory light works fine now. Its just that its a silly set up. You have to have the dome light on to have the cargo light on. I am looking to add a switch so I can have the cargo light on whenever I want, regardless of the dome light. And since I already have a switch there doing nothing, would like to use it instead of making new holes.

Look into a dei 611t. It will convert a pulsed input to a latched output.

OK, I just looked at them online. But Istill dont know what it is. What does it do, in fisher price terms?

Set unit for negative input, latched output. Press button on dash, cargo light on. Press again, light out.

Well, that does sound like what I want then. They are cheap enough, I will get one and see what happens. And, thanks again for your help.

OK, I lied. I cant find anyone local that has a DEI 611T in stock. So, Im going to try to do it with a relay instead. And, I think I got it figured out, just wanted to run it by you and see what you think.

12V source going to post 85 of the relay
Ground going to post 86 of the relay
Ground going to post 30 of the relay
Post 87 of the relay will have a wire going to the black wire on position 3 of the plug for the switch
Then the light green wire from position 7 will run to the BCM as the trigger wire
Then just splice the dark blue wire in position 8 into the wire on position 7

Now, in my head, this will work. But I'm sure just about everybody on this site knows more about this than me. That's why I wanted to run it by the pros first.

No, it won't work. What wire is the "trigger" one at the BCM?

From what I found out, it is a white with black stripe wire, in the pink plug, pin #2, on the BCM.

So that wire with a positive signal will turn on just the cargo lamp?
From the schematics i've seen, the cargo lamp and dome lamp circuits are in parallel with each other. Nothing independent.

Well, from what I've read. I have yet to do this mod, because of wanting to use the washer switch. But several people have done it and said it worked. I got the idea from another board that I belong to. I will post the link up so you can see what it says. I may have missed something that you will see.

https://www.silveradosierra.com/how-to-articles/how-to-add-a-separate-switch-to-turn-on-your-cargo-light-t2232.html

Ok, did more research. Schematics show the WHITE/ black in question to be an output (positive from BCM). It then goes to the junction block ,by the firewall, left of the column (Mid BEC). From there to the roof harness and then the cargo light.
The switch in the link shown is a SPST (on-off) type. The switch for the windshield heater system is a SP-NO (momentary). You need a way to make the momentary button latch, which is why i recommended the 611t.

Oh, ok. I had a couple of relays laying around, and couldn't find the dei 611t in stock anywhere. That's the reason I was trying to use the relay. I will order the dei 611t. But, don't be surprised if I come back here and ask you how to hook it up! Thanks again for all your help.

Ok, I got the 611T in the mail yesterday. Still looking at it to try and do this right the first time. Take a look at my plans here and see what you think.

ON THE 611T:
Black: Ground
Green: Ground
Red: 12V hot
Yellow: Ground

Then the brown wire will hook to the black wire (pos #3) at the switch.
AT THE SWITCH:
The light green (pos #6) will hook to the white with black stripe at the BCM.
And the dark blue can hook to the light green wire.
The yellow wire for the dash lights are working fine now. So I don't need to do anything to it.

And the switches on the 611T
1 shouldn't really matter
2 normally open (up)
3 latched (up)
4 - input (down)

Again, I think this is right, just don't want to burn anything up!

Black: ground, Red: 12V battery, Green: Light green at switch, Brown:
12V battery, Yellow: WHITE/ Black at BCM.

WOW!!! I was way off.... I will get it hooked up this weekend and let you know how it goes. Was I at least right about the switches? And, thanks again.

More explanation on the wiring. Red is power battery, black ground...that's pretty much standard wiring. Green is the input to trigger the unit...the light green at the switch will have a ground on it when pressed. Reading the 611t instructions for the yellow and brown, their connection depends on the type of output (positive or negative). The WHITE/ black (cargo light) is a positive activated light.
A positive output is needed, which is the yellow wire. A battery connection is therefore needed on the brown wire.
Hope this helps.
Mark

OH OK, I think I got this figured out. Lets see, the black at the switch is grounded, when I press the switch it sends the ground signal out through the light green wire. Which goes to the green of the 611T. Then the 611T switches the current to positive, then sends it back out the yellow wire of the 611T to the BCM. Which will send positive power to the light, turning it on.

And by doing it this way, we are actually switching the ground at the switch, as it was designed. So no problems with overloading the switch.

Am I on the right track???

Ok, I got it done, well kinda. I got all the wires hooked up and it appears to be working right. I still have to hook it to the wire at the BCM though. When I hook up my DVM though, I am only getting about 11.37 volts though. To clarify: volts at the cigarette lighter is 12.04 with the truck off. When I leave the black lead hooked up to the cigarette lighter and test for power at the yellow wire, I only get about 9.5 with the truck off and 11.37 running.

Also, if I ground the blue and white wire, the indicator light will come on. So, shouldn't it work with the light green signal wire? Its grounded when on. But, the indicator light wont light that way.

Ok, update. I got all the wires hooked up, and it works just like I wanted it to. Only problem left is the indicator light. If I hook the blue/white wire to ground, it stays on. If I hook it to the green wire, it only stays on while Im pushing the button. Any ideas?

Couple of options. Rewire it on the circuit board...probably pain in the butt. Small relay to invert polarity, or a transistor to invert polarity.

Yeah, I was just thinking about the relay idea. I could use the yellow wire for the hot side, to open up a ground connection. That way it will only be open, or grounded, when the light is on.

Correct...use the relay to convert the positive output to a ground. The relay coil is in parallel with the cargo light, whenever the light is on the relay also activates.

I must be getting good at this electronic stuff.....or maybe just lucky! I will get the relay installed tomorrow and report back. Thanks again for all your help.

It works, it works, it works!! It does just what I wanted. Hit the button, and the led indicator light and the cargo light come on. Hit it again and they both go off. Thanks for all your help. Im sure for most of you guys this would have been a no brainer 10 minute job. But this was a little more than my normal "just throw a switch in there" jobs. Thanks for everything.