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!

Jagdpanzer · 02-09-2019

Here is solution I’m going with to handle the higher amp draw of Spal fans
IMG_2121.JPG
Powermaster 200 amp alternator PN 47864 with PN 186 65mm pulley

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secondchance · 02-09-2019

I am not surprised.

My current alternator was beefed up when rebuilt last year to 145 amp. I have been contemplating a billet alternator putting out 200 amp.

Guess I should spread out mod works. Wouldn't know what to do when done...
Been also thinking about coilover FX3 vs. Van Steele 2 way adjustable coilovers. We shall see...

Jagdpanzer · 02-09-2019

This was Charlie’s fault. He shamed me in to it.

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secondchance · 02-09-2019

Quote:

Originally Posted by Jagdpanzer

This was Charlie’s fault. He shamed me in to it.

Sent from my iPhone using ZR-1 Net Registry

It’ Charlie’s fault I messed with my CHMSL too.

dredgeguy · 02-09-2019

Guilty as charged but mods not my fault, Wazoo started it................

GOLDCYLON · 02-09-2019

Quote:

Originally Posted by dredgeguy

Guilty as charged but mods not my fault, Wazoo started it................

Actually -=JEFF=- started it when he made mine about 12 years ago. I am also running SPAL fans with a normal Alternator with no issues. However I have also been running LEDS everywhere for about 10 years. So....

secondchance · 02-10-2019

Quote:

Originally Posted by GOLDCYLON

Actually -=JEFF=- started it when he made mine about 12 years ago. I am also running SPAL fans with a normal Alternator with no issues. However I have also been running LEDS everywhere for about 10 years. So....

Which LED do you recommend for tail/brake lights and side markers?

-=Jeff=- · 02-10-2019

Yep I started this mod based off of owning an Uplander. I needed a new housing and repurposed the use for my ZR-1.

GC is using my side marker circuits for his cars. I have yet to make a set for me though.. lol..

Yes the Uplander light works great however, I have the OEM set up with light diffuser not the dorman replacement like second chance does

spork2367 · 02-10-2019

Have you done the calculations for any of this? Lets say every auxiliary light on the car (minus headlights and fog lights) draws 200 watts (my ballpark for our cars with brakes being applied probably accurate +/- 20 watts). That's about 17 amps. If you replaced them all with LED's, you could expect to cut that down to 6-10%, so you'd have 1.7 amps. So for approximation sake, best case, you save 15 amps. The 16 inch spal fans are 26 amps. I can't believe the alternator is so undersized that it can't accommodate the fan as is, but if that is the case, saving 15 amps isn't exactly a huge safety margin as you're still asking 8-10% more of the alternators max output.

If you're just talking about the CHMSL, it uses four #891 bulbs at 8 watts a piece for total of 2.6 amps.

If you swapped every exterior light on the car to an LED (including fog lights and headlights), you still wouldn't save the 26 amps a 16" spal uses. Total exterior light usage is 27 amps. Keep in mind, the power supplies used for LED fog lights and head lights are not as efficient as those used in small bulbs and they require significantly more power. So while a tail light LED may use 6-10% of the power of a standard incandescent, an LED headlight will be closer to 30-50%. Especially considering the original headlights were low wattage even by todays standards.

Other solution is...not using your brakes will save you 11 amps!...

Just some food for thought.

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.

02-09-2019	#2
Jagdpanzer Join Date: Apr 2007 Location: Northern VA Posts: 2,661	Re: CHMSL LED mod Here is solution I’m going with to handle the higher amp draw of Spal fans IMG_2121.JPG Powermaster 200 amp alternator PN 47864 with PN 186 65mm pulley Sent from my iPhone using ZR-1 Net Registry __________________ Phil Wasinger 1994 Torch Red ZR-1 WAZOO Member George Braml Intake

02-09-2019	#3
secondchance Join Date: Aug 2006 Location: McLean, VA Posts: 3,723	Re: CHMSL LED mod I am not surprised. My current alternator was beefed up when rebuilt last year to 145 amp. I have been contemplating a billet alternator putting out 200 amp. Guess I should spread out mod works. Wouldn't know what to do when done... Been also thinking about coilover FX3 vs. Van Steele 2 way adjustable coilovers. We shall see...

02-09-2019	#4
Jagdpanzer Join Date: Apr 2007 Location: Northern VA Posts: 2,661	Re: CHMSL LED mod This was Charlie’s fault. He shamed me in to it. Sent from my iPhone using ZR-1 Net Registry __________________ Phil Wasinger 1994 Torch Red ZR-1 WAZOO Member George Braml Intake

02-09-2019	#6
dredgeguy Join Date: Aug 2012 Location: Ellicott City, MD Posts: 1,714	Re: CHMSL LED mod Guilty as charged but mods not my fault, Wazoo started it................ __________________ Charlie __________ Dredgeguy WAZOO Member 1992 Bright Red/Black ZR1 #246 Dana 4:10 gears Polished LT5 by Haibeck Polished Fikse FM5's with Michelin Pilot Sport 2 Stainless Works headers and cats with Corsa

02-10-2019	#9
-=Jeff=- Join Date: Jul 2007 Location: Bartlett, IL Posts: 7,169	Re: CHMSL LED mod Yep I started this mod based off of owning an Uplander. I needed a new housing and repurposed the use for my ZR-1. GC is using my side marker circuits for his cars. I have yet to make a set for me though.. lol.. Yes the Uplander light works great however, I have the OEM set up with light diffuser not the dorman replacement like second chance does __________________ 1990 Corvette ZR-1 #1051 Watson Headers (2" Primary) - Flowmaster Cats - Borla Catback Late Model IH - Plenum Coilovers - 4.10s Custom Interior NCM Lifetime Member #978

02-10-2019	#10
spork2367 Join Date: Jun 2013 Location: PA Posts: 879	Re: CHMSL LED mod Have you done the calculations for any of this? Lets say every auxiliary light on the car (minus headlights and fog lights) draws 200 watts (my ballpark for our cars with brakes being applied probably accurate +/- 20 watts). That's about 17 amps. If you replaced them all with LED's, you could expect to cut that down to 6-10%, so you'd have 1.7 amps. So for approximation sake, best case, you save 15 amps. The 16 inch spal fans are 26 amps. I can't believe the alternator is so undersized that it can't accommodate the fan as is, but if that is the case, saving 15 amps isn't exactly a huge safety margin as you're still asking 8-10% more of the alternators max output. If you're just talking about the CHMSL, it uses four #891 bulbs at 8 watts a piece for total of 2.6 amps. If you swapped every exterior light on the car to an LED (including fog lights and headlights), you still wouldn't save the 26 amps a 16" spal uses. Total exterior light usage is 27 amps. Keep in mind, the power supplies used for LED fog lights and head lights are not as efficient as those used in small bulbs and they require significantly more power. So while a tail light LED may use 6-10% of the power of a standard incandescent, an LED headlight will be closer to 30-50%. Especially considering the original headlights were low wattage even by todays standards. Other solution is...not using your brakes will save you 11 amps!... Just some food for thought.