CHMSL LED mod - ZR-1 Net Registry Forums

secondchance · 02-09-2019

I am contemplating Spal fan install this spring and I am hearing, due to heavy amp draw, higher capacity alternator and reducing electric load is advisable. One suggestion made to achieve the latter is to modify CHMSL to LED. In stop and go traffic with foot on the brake, CHMSL represents healthy electrical load is what I was told.

I heard some using Chevy Uplander, Pontiac Mini Van and Olds Silhouette CHMSL (same part) LED strip to work with our Z CHMSL.
I ordered Chevy, Pontiac, Olds CHMSL from Ebay for about $60 (of course a Chinese knock-off).
https://www.ebay.com/itm/New-Rear-3r...72.m2749.l2649

Once disassembled and laid next to Z CHMSL housing, turns out LED strip out of GM CHMSL is about 1.5" too long.

Hmmm... What to do... I am no electric engineer but careful observation of the circuit board leads me to suspect 4 LED bulbs and a resistor represents one circuit and multiple circuits are connected to the power and ground in parallel. If I remember high school physics class, parallel circuits are such that if I cut excess strip circuits prior to cut should still light up.

Time to bite the bullet and try my theory to rest. If I am right - all good. If not - $60. I take a leap of faith (or is it cut of faith) and snap off excess length of the circuit board with a wire cutter. Hook up 9V battery and "dang!" I am right!

Time to gut OEM CHMSL and secure LED strip into the housing. Although tough to see, I laid down two layers of 3M double stick on the bottom of red plastic housing to keep LED strip from moving around, temporary 3M strip perpendicular to the strip to hold in place.

Also, attached 1/4" foam on the inside face of CHMSL upper housing so that, once screwed together with red plastic housing, foam will compress and keep the LED strip secure between the top and bottom pieces of the housing.
Also used insulated spade connectors so that I can switch the polarity if necessary because LED require correct polarity unlike halogens.

End result.

A close up.

Not bad for 2 hours on Saturday morning!

02-09-2019	#1
secondchance Join Date: Aug 2006 Location: McLean, VA Posts: 3,723	CHMSL LED mod I am contemplating Spal fan install this spring and I am hearing, due to heavy amp draw, higher capacity alternator and reducing electric load is advisable. One suggestion made to achieve the latter is to modify CHMSL to LED. In stop and go traffic with foot on the brake, CHMSL represents healthy electrical load is what I was told. I heard some using Chevy Uplander, Pontiac Mini Van and Olds Silhouette CHMSL (same part) LED strip to work with our Z CHMSL. I ordered Chevy, Pontiac, Olds CHMSL from Ebay for about $60 (of course a Chinese knock-off). https://www.ebay.com/itm/New-Rear-3r...72.m2749.l2649 Once disassembled and laid next to Z CHMSL housing, turns out LED strip out of GM CHMSL is about 1.5" too long. Hmmm... What to do... I am no electric engineer but careful observation of the circuit board leads me to suspect 4 LED bulbs and a resistor represents one circuit and multiple circuits are connected to the power and ground in parallel. If I remember high school physics class, parallel circuits are such that if I cut excess strip circuits prior to cut should still light up. Time to bite the bullet and try my theory to rest. If I am right - all good. If not - $60. I take a leap of faith (or is it cut of faith) and snap off excess length of the circuit board with a wire cutter. Hook up 9V battery and "dang!" I am right! Time to gut OEM CHMSL and secure LED strip into the housing. Although tough to see, I laid down two layers of 3M double stick on the bottom of red plastic housing to keep LED strip from moving around, temporary 3M strip perpendicular to the strip to hold in place. Also, attached 1/4" foam on the inside face of CHMSL upper housing so that, once screwed together with red plastic housing, foam will compress and keep the LED strip secure between the top and bottom pieces of the housing. Also used insulated spade connectors so that I can switch the polarity if necessary because LED require correct polarity unlike halogens. End result. A close up. Not bad for 2 hours on Saturday morning! Last edited by secondchance; 02-09-2019 at 02:39 PM.