I was planning on posting electrical diagrams and some other information about this project. I had been reluctant until everything was 100% complete. I’m now working towards my final posts on this.
So here was the problem... As mentioned, the original heater module I purchased was for a Cadillac DTS. When the module is activated (or deactivated) with the operator switch, it sends a PWM (Pulse Width Modulated) signal to the DIC to display an appropriate message. Unfortunately, the Bonneville DIC is incompatible. I purchased another heater module made for the new pick-up trucks. These vehicles have a switch on the console which is how they are activated (as opposed to a switch on the wiper/signal control arm in the Cadillac). What’* nice is that there is also an indicator lamp in the switch which flashes when the heated washer cycle is active. This makes the version of the module from the pick-up trucks much better for the Bonneville application.
This is where the next hurdle complicates things. While the module will flash an indicator about once every second during the cycle, GM has changed the way they do this in many of the newer vehicles. Traditionally, when an indicator was illuminated (on older vehicles), the BCM applies a 12 volt signal to the lamp or LED. On the newer vehicles, 12 volts exists at the indicators (and instrument panel backlighting) all the time and when illumination is required, the other side of the circuit is grounded. This means the traction control switch I spent so much time working on is incompatible (electrically) with the new heater module indicator lamp circuit :(
Well, I’ve already spent a lot of time on this and since my switch has an indicator I decided not to give up just yet. I modified the circuit board inside the switch by adding an extra pin. This allowed me to use a larger six cavity connector compared with what the traction control switch originally had (which was a four cavity connector) to accommodate the additional wiring. By adding the extra pin, I was able to connect a constant 12 volt signal to the switch. I then have the heater module control the ground for the indicator the way it does in the new vehicles. I needed to cut a couple of traces and add some wiring. I used 30AWG wire wrap wire.
Here is the switch in its original form:
Now with some modifications:
The new pin configuration is as follows:
1 – Indicator Lamp Control (From the heated washer fluid module)
2 – Empty/Blank (No pin in this position)
3 – Back Lighting Signal
4 – Accessory Voltage (+12 VDC)
5 – Switch Signal (To the heated washer fluid module)
6 – Ground
This is the new connector I need to use in order to add the additional electrical signal:
On the back of the switch, there is a moulded area the electrical connector plugs into. I cut away a portion of this on one end. I then used another switch and cut off a portion of this moulded area to transplant onto the original. Everything bonded very well using J-B Weld. The housing now accommodates a six cavity plug. What’* really nice is that the connector keying mates properly so it isn’t possible to plug the connector in backwards. It also clips on with the securing tab so the connector can’t work itself loose.
Unfortunately the J-B Weld I used was the fast setting version. This was good and bad. It made the project go fairly fast, but I couldn’t make it look as good as I hoped since it set very quickly. This means I’ve lost a little of the OEM appearance. Hopefully nobody has to take my dash apart and sees this
The great thing about all of this is that my indicator lamp now works. It really bothered me that my switch had an indicator and it wasn’t working.
While I was under the dash, I decided to work on some other wiring a little. There are two large connectors behind the knee bolster, in front of the steering column. This is where I tapped in to obtain wiring access for various modifications I’ve done, including the heated washer option. I decided to add a couple of “Accessory / Modification” connectors to make things easier. It’* a bit troublesome to splice into these so the connectors I added have the signals present for the turn signal mirrors, heated washer option and a few others which I thought I may need easy access to later.
The signals I decided to tap into include:
FROM C202 – BLK GT 150/280 SERIES CONNECTOR:
Windshield Washer Pump Control
Windshield Wiper Switch ON Signal
Windshield Wiper Switch Signal 1
Windshield Wiper Switch Signal 2
Windshield Wiper Motor HIGH Speed Signal
Park Lamp Switch ON Signal
Back Light Lamp Control
Ignition 1 Voltage
FROM C200 – WHT GT 150/280 SERIES CONNECTOR:
LEFT Turn Signal Lamps Supply Voltage
RIGHT Turn Signal Lamps Supply Voltage
Courtesy Lamp Supply Voltage
I may add two more in the future for VSS and Class 2 Serial Data.
I also decided to rebuild the heated washer option wiring harness to include the wiring for the turn signal mirrors as well. This was more of a “housekeeping” process though. It’* a little cleaner to have a single wiring harness instead of multiple ones running through the dash. Clips are attached which makes securing the harness to the dash easy. The auto wrecker is a great source for clips and miscellaneous wiring items.
The pictures below are the harness for the heated washer fluid system and turn signal mirrors. There are various shots which include some of the inline connectors I used to make connection easy (particularly where the wiring attaches from the firewall pass through).
As soon as I’m done drafting all the diagrams, I’ll post those as well.