1. My rear lights all worked. That is, brake lights, reverse lights, parking lights, turn signals.

2. My headlights kept going out because the headlights switch had contacts inside that were not touching correctly.

3. Pulled headlights switch, opened it up, cleaned everything, rebent contacts that had moved apart, headlights worked again.

4. But then suddenly my brake lights didn't work but my rear parking lights did. Checked all door panel fuses, even swapping them with fresh fuses in case a fuse melt point was not visible.

5. Needed to leave parking lot so I reversed. Reverse lights didn't work now.

6. Stopped at a gas station to test my brake lights again. Now my rear parking lights were out.

7. Tested my turn signals, worked in front, but they were out in the back now.

8. So what did I have in the front? Working front turn signals, working front headlights, working front turn signals, working high beams, working front parking lights, working multi-switch/turn signal switcher because obviously it controls all those things.

9. So what did I have in the back then suddenly? No reverse lights, no rear parking lights, no rear brake lights, and no rear turn signals.

10. And what did I check? All the fuses in the side door fuse panel, which is the only fuse panel in a '97 Chevy Blazer (unlike the '98+). And I jiggled the multi-switch a bunch of times as someone had suggested.

11. And about four or five months ago I changed the rear parking lights/turn signal lights to fresh bulbs.

Anyone have any ideas? I drive for work and I can't drive if I have no brake lights, parking lights, or turn signal lights in the back.

 

No fuse is common to all those rear light faults. There is also no common switch and few common power wires. What is common to every one of those problems is the ground point G333 listed as: Left "D" pillar near tail lamp. I would:

1. See if you have power to the disabled bulbs when called for and ground the meter to a clean frame point.
2. If you have power then check the common ground point for corrosion and contact
3. If that ground is good then check the connection between the bulb ground side and the common ground. First order check is resistance but a better check is the voltage of the bulb ground side when called referenced to a clean frame ground

If I am wrong and there is no power then we work the power side circuits. Let me know what you find.


George

 

Thanks very much for your reply! The one thing I'm wondering about is how it's coincidentally possible that within minutes of completing work on my headlight switch fix and getting ready to celebrate that successful repair, the entirety of all the lights in the back go out due to a grounding problem in the back. It just seems statistically improbable.

For a couple of minutes I still had parking lamps back there but no brake lights. I drove down the street to a gas station and checked again and now there were no rear parking lights or reverse lights. Though there were front parking lights.

I see that a lot of people keep mentioning the hazard switch on these vehicles as a possible cause. Just like many Blazer owners, I experienced the intentionally-designed-to-break-easily GM hazard switch problem years ago. The entire top half of the hazard switch broke off leaving only a flat jagged nub deep down in the steering column.

And then something within that broken hazard switch caused my horn to activate at full blast, continually last year. I had to pull over on the side of the road and try to keep the hazard switched pressed down manually in an in-between state, which of course it didn't want to lock into. My only solution in the moment to stop the horn from activating was to super glue it in place. It worked, but it also permanently locked that hazard switch in place. I say this because a lot of people I see are suggesting that the hazard switch be moved around in order to see if the brake lights and rear lights activate again.

Something else I noticed a couple weeks ago is that my cruise control no longer works. And that is controlled within the multi switch, which also controls my turn signals, wipers, high beams, and is part of the hazard switch unit.

I will work through your recommendations this afternoon and let you know what I find 👍

 

The first thing I looked for was something common to your whole story but it does not exist. It was a reasonable starting point. The MF or hazard switch are not even involved in all aspects of this. That ground point and its wiring is 100% common to every issue. I have no explanation for the coincidence if I am right, other than coincidence. If I am wrong we will head the other way to the power side which sends us up to that area. That's why I made step one check for power so we don't waste any time on grounds if I am wrong but Occam's razer baby. I am usually right but not always. Go big or go home. LOL.

George