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time to get cereal
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I don't have the relay in mine at all, still works.

The CHMSL is controlled by the white wire that comes straight off of the switch on the pedal.
 
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This is the confirmation I needed. I don't understand how removing the CHMSL relay prevents both brake lights from working (according to my wiring diagram). BUT, in addition to pulling the relay, there is a blue wire at the tail light harness connector that carries the brake-only signal. Combine those two elements, and the wiring/install is a snap.
I do want to confirm that all I need now are Blazer tail lamp sockets to plug into the lights...
I'll be out at the shop today and checking my stash of bulb sockets I used.

I was told to jump some terminals at the relay but chose to do it the way I have done before rather than trying to get to the backside of the fuse/relay block. I did this on my Datsun 620 except there was no CHMSL so I had to run a new brake light wire from the switch to the rear brake lights. If you remove the relay wouldn't the CHMSL no longer work?
The diagram I posted isn't the easiest to follow, but the CHMSL relay doesn't power the CHMSL itself. It is turned on by the CHMSL circuit and powers the brake portion of the rear brake/turn bulbs through the multifunction switch.

This is only true on the pickup as the Blazer brakes are powered directly through the brake switch. I think this is because the Blazer uses an LED CHMSL, so lower current is required to power the whole system. On a Blazer cutting the white wire going into the multifunction switch pin A1 has the same effect as removing the CHMSL relay on a pickup.

Regardless you got it working well, but wanted to share for others in the future. It makes the process a one wire update.
 

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Old Fart
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Discussion Starter · #243 ·
This is only true on the pickup as the Blazer brakes are powered directly through the brake switch. I think this is because the Blazer uses an LED CHMSL, so lower current is required to power the whole system. On a Blazer cutting the white wire going into the multifunction switch pin A1 has the same effect as removing the CHMSL relay on a pickup.

Regardless you got it working well, but wanted to share for others in the future. It makes the process a one wire update.
The Blazer already has the correct wiring for separate turn signals so no wiring modifications are needed you would just change the tail light housings to ones with amber turn signal lenses I would think.
 

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The Blazer already has the correct wiring for separate turn signals so no wiring modifications are needed you would just change the tail light housings to ones with amber turn signal lenses I would think.
It doesn't. The brakes and turns are on the same circuit for the Blazer too. I had to tap into the CHMSL circuit for the brakes and remove the white wire I pointed out before to isolate the turns.
 

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Old Fart
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Discussion Starter · #245 ·
It doesn't. The brakes and turns are on the same circuit for the Blazer too. I had to tap into the CHMSL circuit for the brakes and remove the white wire I pointed out before to isolate the turns.
I thought I had seen Blazers with separate turn signals in the rear?
 

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LS1 powa!
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I really gotta get on here more often. Nice to see a set of those taillights in the wild they look good!! I just got a set of each for my trucks since I hate the way the lights are stock. The lights are meant to use the blazer bulbs and connectors (I'm guessing brazil trucks use "blazer" wiring harnesses since those are the only ones gm made to support separate bulbs). Since I'm replacing the entire truck harness with a Jimmy harness on my truck the lights are "plug and play" no mods necessary.







How did you wire yours? Did you get a blazer/jimmy 4 pin flasher and run the missing wiring? Or did you splice into what was there. Do your brakes override your hazards if you have them both on?

I grabbed Blazer harnesses this week to try this out. I was only able to get 2/3 of the sockets to fit without modification. I was unable to make any of the sockets fit into the reverse housing. It looks like an easy fix, filing the socket tabs. But thanks for showing this to us! It cut my work to make these fit way down.
 

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LS1 powa!
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I would just remove the CHMSL relay all together. I pulled the one on my truck, and the brake signal still existed at the CHMSL and at the LT blue wire near the trailer plug.
 

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Old Fart
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Discussion Starter · #253 ·
I forgot to post that I received the GM 1156 and 1157 sockets and the tabs were the right sizes but they were clocked 180 off so they wouldn't work either. Unless someone comes up with another solution the only way I know to make them work is to file down the tabs to fit the holes in the Brazilian lights. It would be so much easier if the guy in Brazil would find the correct light sockets to fit and sell as a package.
 

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LS1 powa!
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So for anyone wondering about sockets that fit, you will need two of the grey sockets, and one of the white sockets. You will need to pull these sockets from two different Blazers, since a Blazer taillight harness has one grey, and two white.
The socket for the reverse & haz/turn lights will need to be soldered in, but the socket for the brake/park lights can simply be swapped out by taking the connector assembly apart.

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Funny you bump this today, because I got my hands on the part numbers for the Blazer export sockets, yesterday. They use the round style 1156/1157 instead of the spade style the domestic trucks use.

Part numbers are 12160386 for the single filament and 12160390 for the double filament.

I didn't use those on my Blazer, though. I did what @BTE did and used the Blazer sockets. No modifications for me, but mine were the Blazer tails, so could be a difference there. I was also able to take all of my sockets apart and move the terminals around.
 

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It has been suggested that I should start a build thread since I'm doing the engine swap on my truck, so here goes.


For those that haven't seen pics of my truck I will start with what it looks like now.


That is a clean machine! I’d like to know if you’re happy with your replacement headlights and where you got them. Especially, one OF to another, if they are bright enough. Thanks!
 

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Old Fart
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Discussion Starter · #257 ·
That is a clean machine! I’d like to know if you’re happy with your replacement headlights and where you got them. Especially, one OF to another, if they are bright enough. Thanks!
Thanks, The lights are from eBay and they have a good pattern and put the light where you need it. I swapped in LED bulbs and did the quad conversion so the lows stay on with the highs. Here is what the low beams do.
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Discussion Starter · #258 ·
I just realized I forgot to post pics of my eBay headers when they came. The quality of the workmanship is very good so if there are no fitment problems when they get installed I will have saved some bucks. If I'm not happy with them then I'm only out $100 and I will replace them with the Hooker/Holley midlength headers.

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Been there Done it
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Looks like the same ones I bought off Fleabay. Drivers side is no issue. Passengers side wants to argue with everything in sight.
If you have your engine on a stand try installing them complete with coils, plugs, wires, and dipstick. Then when you see what a PITA the plugs on that side are going to be, send them back.
I was so unhappy with the plug and wire interference that I sprung for the Holley S10 manifolds. The headers are going on Craigslist as soon as the weather gets a bit warmer. Dropped back into the low 40's for the next week here. Since this is a hobby I'll work on it when it warms a little.
 
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Old Fart
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Discussion Starter · #260 ·
It will be too late by the time I can do a test fit to return them so I will probably end up doing the same thing you are except I want the headers for mine.
 
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