so you're saying despite having cleaned all the goop off the ends (where the crimped connector wraps around wire) it's still down inside that wire end? Main engine ground (trans to rad support) is brand new. Are the headlights on the BCM ground?

I need some good connectors. Can anyone recommend what to use. I won't settle for the kind you buy at wal-mart. And, if I had to cut the wires too short couldn't I just re-solder an extension or would that cause resistance?

 

Replaced all connections to the grounds on the strut and over by the fuse box. Had to cut back a good 2-3 inches until I got to good wire. Not too much green stuff but the wires were rusty. There was a fine dust like residue coming off of them. Soldered the appropriate sized auto wire back on and sealed with heat shrink and crimped along with soldered new ends on.

Replaced the positive side crimps as well. Some corrosion down into the wire with those too. Bad news is it did not solve the flickering light issue when applying brakes. Good news is that I no longer have a draw on the battery anymore. Meter is reading zero now after car goes to sleep. So I'm thrilled about that. Did this yesterday. Checked battery voltage this morning and had a good 12.6 volts.

Kept thinking over the weekend about this light flickering thing. If it's only happening when I apply the brakes it seemed I should focus more on the brakes. I put a new brake position switch in and calibrated it. Although it didn't help with the flickering lights, it did make the gear shifter unlock much better and is much more quiet. I put a cement block on the brake pedal and went to the back with my meter. Checked rear brake light harnesses for voltage and got battery voltage. Checked for voltage drop and there was none.

Different story on the 3rd brake light. With braked pedal on and key on and all 4 3rd brake light bulbs blasting, I back probed at harness on light blue wire and got 10.5 volts. Ground tested good. Checked for voltage drop and got 2.0 volts on the positive side and .4 volts on negative side. Disconnect harness and test coming from car side and get a full 12.5 volts and good ground and no voltage drops on either side. The voltage drop happens after you plug in the harness. I unplug one bulb at a time and the voltage drop starts to come closer to zero, about .5 volts per bulb. Is this how it should work?

At this point I decide to leave the harness unplugged and start the car to see if I have the flickering problem and guess what? Lights not flickering and fuel pump speed not interrupted anymore when I apply the brake pedal. I'd swear it's tied to that 3rd brake light. For now, 3rd brake light is disconnected. I'll probably get stopped now tomorrow! Tried to locate the harness assembly but no luck. Looks like you have to buy the sockets and daisy chain them.

I'm not real good with diagnostics but voltage drop testing isn't too difficult. It seems to me that brake light bulbs shouldn't cause a 2.0 volt drop because they're lit up. I'm leaning towards the idea that when that 3rd light was stuck on (don't know how long that was but it was HOT) maybe something melted and causing issues now.

 

Now you’re on to something , perhaps it would be a good idea to replace that third brake light assembly as it might be faulty after that high heat issue

https://ebay.us/m/MPZK8u

 

Replaced the brake light harness. Got one a junk yard which was in much better shape than my original. Looks like new. Still have the 2.0 volt drop on the positive side of harness when brake light is on. Is there supposed to be a voltage drop when the bulbs light up? Double checked the bulbs which are 921LL and they are all new. I doubt the long life bulb would change anything vs a regular 921. So I'm still driving around with the harness unplugged.

Just to recap how I'm checking voltage drop. I run a wire from positive post of battery to one end of meter. The other end of meter I put to positive side of harness. Meter on DC volts. Same process on negative battery post and negative side of harness. 2.0 volt drop on positive side, .40 volts on negative side with 3rd brake light on. Unplug the bulbs and no voltage drop. Makes sense since the bulbs pull the voltage but I didn't think the voltage the bulbs use would show up as voltage drop. Unplug the harness and test car side where harness plugs in with brake still on and I get battery voltage on positive and no voltage on ground. Also no voltage drops.

Clearly, it's the 3rd brake light coming on that's making headlights flicker and fuel pump interruption. Night and day difference when plugged in vs unplugged.

The relay for the 3rd brake light feeds the 3rd brake light obviously, right? The wire coming to 3rd brake light tests good. Why does lighting the 3rd brake light change everything?

What am I missing or doing wrong?

 

Did you replace the third brake light assembly or just the harness?

 

Just the harness. Also doing the testing with the harness hanging out of assembly. Why would replacing the assembly matter? These are just plastic sockets that clip into the lens, right?

 

Plastic sockets that hold the bulbs that over heated and could cause connection problems. Melted light sockets are a major cause of voltage issues.

 

Ok, I think we misunderstood each other. When I say I replaced the harness I'm referring to the entire 4 socket wire with the electrical connection. I believe this is what you are referring to as the assembly, correct? I'm picturing assembly to be the harness + the whole brake light on the window.

So yes, all 4 sockets and wire are replaced.

I guess it's possible the junk yard one could be experiencing the same issue, but it looks mint condition, no burn marks around the sockets. I specifically looked at both HHR's they had and took the better of the two harnesses. I suppose it could maybe be in the connectors too. I might just crimp on some spades or better yet just direct solder.

 

I posted a link to the assembly pictures from eBay , check the ground wire for the third brake light

https://www.chevyhhr.net/forums/how-...cations-56504/

 

So yes, all 4 sockets and wire are replaced.

I guess it's possible the junk yard one could be experiencing the same issue, but it looks mint condition, no burn marks around the sockets. I specifically looked at both HHR's they had and took the better of the two harnesses. I suppose it could maybe be in the connectors too. I might just crimp on some spades or better yet just direct solder.[/QUOTE]

The late 90's tahoe and pick-ups had taillight sockets with 100% failure rate inherent in it's poor design. Weird how fuel pump and third brake light relate here.
The Canadian Neil Young wrote rust never sleeps, nor does corrosion in the wiring of aging machines I suppose.
Best is that you're closing in on solving this gremlin(s)