1995 Eldorado - Turnsignal fast, electrical problem?

[BodybyFisher]

So this was a very weird problem, here are the symptoms

1. The RIGHT turn signal flashed fast when you used it - this usually indicates a blown bulb, all bulbs flashing indicating all filaments were good
2. The RIGHT front was flashing fast but DIM
3. The problem was compounded at night, turning on the parking, head lights or fog lights turns the dash RIGHT turn signal indicator on and the RIGHT turn signal on steady.  After a while, I got the DIC message "TURN SIGNAL ON".  (physically, the signal was not on).   Cycling the turn signal left then right, removed the DIC message for about 5 minutes when it came back.
4. When I put the LEFT turn signal on it operated normally, but the dash HAZARD warning indicator came on with it. 
5. I had an I022H code - Panel Dimming Switch Pot Circuit.
6. The RIGHT cornering light was intermittent.

A side benefit of all of these electrical gremlins is that I have been reading the 94 Factory Service Manual and looking at the schematics for a couple of weeks and I am starting to get a good feel for and understanding of using the schematics for diagnostics.

The problems were very weird, I couldn't help but think that either wires were shorted to ground (which should have blown a fuse) or shorted together or a relay was stuck on given the seemingly unrelated weirdness I was having. 

Here is how I proceeded:

• There was evidence that water had gotten into the RIGHT cornering/turn signal lens assembly but it was dry at the moment.
• It appeared that the RIGHT turn signal socket was replaced due to the colors of the wires, peeling back the electrical tape confirmed that as the wires were soldered and taped
• Because of the I022 I removed the headlight switch and disassembled it.  I cleaned 3 contact fingers and circuit board contact point that connects the pot to the circuit board, the contact point looked a little corroded or oxidized.  Doing so reestablished the connection I believe.   If you do this be VERY careful, there are two tiny tiny ball bearings in front of tiny springs, these are used to create detents for the park/headlight position locations.  You have been warned, I was on my hands and knees finding one that got away.
• I found the RIGHT cornering light filament detached, that is what caused the intermittent, I replaced the bulb
• The battery has two grounds, one to the engine, and one to the body, right behind the RIGHT headlight. The harness I was working on for the RIGHT light assemblies, was also grounded there.    It looked corroded, so I removed the nut and cleaned and restored the ground.   In doing so, I noticed that the ground going to the engine is very bad, the wire is bare at both ends and midway, you can see that the wire has been overheated, its bumpy from oxidation it seems, which would add resistance to the ground.  Ill post photo.  That ground should be replaced, but the owner is selling the car.
• Looking at the schematic, I noticed that the side marker light and parking lights are fed from the same common source, a splice at S107 and the ground splice was nearby.  Hmm, the side light works but the parking light does not work?     Here is where I made a mistake, testing ground on the socket, and the ground was weak, in addition, testing voltage using the socket ground and power at the socket I only had 5 volts.  I assumed that, because the socket was replaced, it was good, and that the problem was in the ground and power splices near the light assembly plug according to the manual.  It didn't occur to me that the socket was bad in some way.   I pealed back all the tape and all splices looked good.   Weird that I had power to the splice for the side light but no power to the parking light. I suddenly realized that if I use battery ground to test for power at the socket, I had 12 volts and that the ground at the socket way bad.  This is the headlight assembly with its wiring peeled back.
• 
• Testing the bulb socket ground showed high resistance, I discovered that the socket I assumed was good, had a rusted and corroded ground as seen below.  Water can get into the corning / park/ turn signal light assembly and destroy this socket, my 97 has the same problem, needing a socket.
• 
• I had a new socket that I ordered for my 97, that also was damaged from water.  So I spliced the new socket in, plugged in the assembly and the parking light worked but the turn signal was still fast.
• Remembering that I had read that it was possible for the wrong bulbs or for them to be installed wrong, I pulled the RIGHT rear light assembly.  I was not optimistic because, all 3 bulbs lit up fine... Well was I wrong.   All three bulbs had there contacts worn almost flat, and the increased resistance was overheating the socket contacts.  I was very surprised by this, cleaned all contacts and replaced all three bulbs that looked like this.   I recall seeing this a long time ago on another car. 
• 

All odd problems were gone now, no more fast turn signal, the odd behavior of the turn signals where if you turned on the parking or head lights it turned on the dash right indicator was gone, and the left turn signal turning on the dash hazard indicator was gone, in addition the I022 was gone.   Hooray!

I learned a lot in this diagnostic, the main thing was to assume nothing.  Don't assume that because the socket had been replaced that it is good, that was a big mistake.  Don't assume that because a bulb is flashing that its good, because all three rear bulbs flashed but their worn melted contacts added resistance to the circuit, and finally try to avoid thinking the problem is caused by big stuff like the turn signal switch in the column, flasher module, head light switch, etc, because resistance due to bad contacts and corrosion will cause electrical craziness.

Disassembling the right front allowed me to get in there to test from the light assembly connector and inspect where the wiring harness crossed into the engine bay that it might have been cut into by the sharp metal edge on the radiator support you can see the harness next to sharp metal below.  Because of all of the ODDNESS, I assumed it had to be caused by something big when it was a bunch of small stuff!  I learned a heck of a lot!  Hope this helps someone.

 

[Logan]

The sockets on those are known to go bad. And for the most part....look fine.

I attached a pic....on the far socket you can see discoloration in the plastic. Easy to pass a quick inspection....but it is a bad socket.

 

[KHE]

Excellent troubleshooting Mike and good information for the archives!

One tool I need to add to my toolbox is a test light.  For years, I have scoffed at them - preferring to use a volt meter to do troubleshooting but - a volt meter will lead you astray when diagnosing trailer lights - a high resistance connection will show the correct voltage but it won't pass the current necessary to light up a bulb.

[BodybyFisher]

7 minutes ago, KHE said:

Excellent troubleshooting Mike and good information for the archives!

One tool I need to add to my toolbox is a test light.  For years, I have scoffed at them - preferring to use a volt meter to do troubleshooting but - a volt meter will lead you astray when diagnosing trailer lights - a high resistance connection will show the correct voltage but it won't pass the current necessary to light up a bulb.

That is so true @KHE Here is Load pro by Dan Sullivan this is soon to be in my toolbox.  He has some terrific youtube videos, here is one.  LOADpro Operation and Voltmeter-only diagnostics!!! 

 

[BodybyFisher]

1 hour ago, Logan said:

The sockets on those are known to go bad. And for the most part....look fine.

I attached a pic....on the far socket you can see discoloration in the plastic. Easy to pass a quick inspection....but it is a bad socket.

 

So true Logan, that socket looked terrific!, the ground was rusted badly.   I'm learning!

[BodybyFisher]

Here is a follow up to this job.  The start of the problems on this car was the transmission not shifting into 3rd gear, the tranny would get to a point and sort of freewheel. When the engine warmed up, shifting became normal. This has been happening for about a year, but it has been intermittent. No solenoid codes.  The pan was dropped, the fluid was clean as a whistle, nice an red, no sediment and the solenoids were not cracked.   It should be noted that the owner had a problem at the same time with the positive cable being badly corroded to the point where he was unable to start the car after a heavy rain and I needed to go rescue him. 

Well during my diagnosis of the turn signal problem above I noticed that the battery grounds were dirty and damaged.  As we know, there are two grounds one to the FRAME and one to the ENGINE.  I cleaned the frame ground that was dirty and pretty corroded.  But the engine ground looked terrible, with creeping green corrosion and it looks like either an overheated wire that is probably due to an increase in resistance or its corrosion under the insulation.  Either way this engine ground is not providing a good ground.   I believe that this bad ground in conjunction with the bad positive connection at the battery could have caused the shift solenoids to malfunction and affect shifting. 

I hope to have the owner replace this ground, its cheap on rockauto and when I replace it I will do an exploratory of this wire and see what is under the insulation and what the resistance voltage drop is.   Excuse my text in this photo, it was way too small.  The top arrow shows creeping green corrosion and the bottom arrow shows either overheated wire or corrosion under the insulation.