CHMSL Wiring

Bretter

Well-Known Member
Building on the following discussions:
http://www.dfkitcar.com/forum/index.php?threads/brian-ns-a-very-stock-extended-city-goblin-09-ss-tc-donor-okc.508/post-8009
http://www.dfkitcar.com/forum/index.php?threads/brian-ns-a-very-stock-extended-city-goblin-09-ss-tc-donor-okc.508/post-8015
and more that follow in that thread...

I did some testing on our 2008 Sport model with the donor CHMSL that we still have.

No CHMSL connected:
1. Lights on, no brakes: 7.2V on the Light Blue supply wire going to the CHMSL
2. Lights on, with brakes: 12.2V on the Light Blue wire
3. Measured resistance of CHMSL only (not connected to anything): 1.0ohm

With CHMSL connected:
1. Lights on, no brakes: <0.1V on the Light Blue wire, <10mA current flowing through light (measured ~4.5mA)
2. Lights on, with brakes: 12.2V on the Light Blue wire, current through CHMSL: 1.75A

Conclusion:
1. Yes the CHMSL grounds the 7.2V when no brakes applied. Indicates light bulbs are good.
2. ECM controls current in all conditions - <10mA when 7V present, <2A when 12V present

Putting a 6ohm resistor to ground in parallel to CHMSL may be required depending on LED version of CHMSL. i.e. what does the CHMSL do when 7V is applied to the unit? If it tries to turn on, the ECM will limit current and probably cause it to shutdown. Maybe it goes into hiccup mode of some sort?
 

Briann1177

Goblin Guru
I gave up trying to figure out how exactly that circuit works and how it integrates with cruise control. To this day, I still don't understand it. For something as silly as a brake light, the circuit sure is complicated.

Instead I just purchased a Cobalt compatible LED brake light from an Impala and went with that. Its not nearly as sleek as some of the aftermarket strips, but it was a whole lot easier.
 

SliderR1

Well-Known Member
I'm about to get into this on my Goblin. I was planning on just using the supplied CHMSL built into the wing that came with the kit. Anyone got cruise to work with this setup?
 
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