Not sure how you are checking the resistance, but it should only be on the plug side(going to the switch itself, it should not be connected to the harness.

I have no idea how you could read 25 volts at the bulb connector.

 

It was unplugged when I checked the resistance. I plugged the blinker switch back in after I checked the resistance so I could turn on the lights. Then I took one of the bulbs out of the left rear tail lights while the lights were still on and put my volt meeter on it and it said 25.7 volts. then I went to the front of the car and checked the battery and it had just a little over 12 volts...I thought that was what you meant by checking the voltage at the bulb socket.

 

From how you describe the symptoms the problem is most likely at the MFS area not at the rear. It sound as though the MFS is somehow routing the flasher down the white wire not the yellow. You need to just calmly go through what Lucky has sugested. Good luck.

 

I have tried to do everything like Lucky has told me too he is obviously very knowledgeable about the subject and has spent allot of time already trying to help me and I appreciate it. I checked the resistance of the switch on the switch side with the switch disconnected with the blinker on the left side and then I checked it with the blinker on the right side which all seems to be OK between 00.2 and 00.0 and the blinker on both right and left signals the readings were the same. This is my dad's car that he just bought from a jerk who took advantage of him... I also have a C5 All I was mentioning was that when I take the bulb out of my car and check the left rear socket with the lights on it shows just at 12 volts but if I do the same thing and check dad's car it has 25.7 volts at the rear socket. I thought that might help Lucky while he is trying to help me...Trust me I appreciate any input from the members the wealth of knowinger in this forum is priceless to people. Just trying to save my dad from having to take it to a dealer and get ripped off even more...I am sure they would charge him a fortune to check everything I have already checked and who knows how much to fix it.

 

Do you have Euro tail-lights or standard tail-lights? I'll try to give some suggestions once you answer this one.

I have no idea how you get 25V on your meter. That's basically not possible on that car. You sure the meter wasn't showing you milli-volts? Lock the meter to the 20V range when you're working on a car to avoid that type of confusion.

I also suggest you get a long piece of wire and run it from the negative battery post to where you are troubleshooting. Use it as the ground. Then, you can measure to the power wires to confirm 12V power. If you have a bad ground at a light socket you can be thrown off by not measuring 12V power at that light socket when you use the light socket ground wire. So, using a good ground helps you confirm you have or don't have power. You can also measure the local ground wires to confirm you get 0V. If you see 12V on the ground of a light socket then the grounding of that wire is bad. You typically need the circuit connected (bulb in the socket) to do this test.

For the front. The grounds are a splice pack by the hood hinge on each side of the car on the top of the frame rail. It's a black block with a bunch of black wires on one side and a metal tab bolted to the frame on the other side. Those things have caused numerous troubles for different people so they are a likely suspect. You could try unplugging and plugging the left one a few times. Your description doesn't sound like a ground but this is easy to check.

Peter

 

You'd think so except routing the flasher to the white wire would flash both the right tail lights and the center brake light.

Peter

 

That's a good point. To the OP if the left turn signal is on, do the right brake lights work?

 

Ok gentlemen, to summarize what the OP has disclosed:

1) Has changed all bulbs already
2) Left front marker light not working, all other markers function.
3) Tail lights work
4) Brake lights work
5) With hazards on:
a) Both front lamps flash
b) Right rear flashes
c) Left rear does not flash


The front marker and park lamps, all receive 12 volts from the same source, and they all ground at the same location SP102. Has the OP tested the left marker socket for 12 volts/ground?

The left rear turn signal lights do not function, or flash with hazards. The feed to the turn signal lamps(yellow wire/circuit 18), is also the feed for the brake lights and hazards. So if the brake lights work, and the hazards only flash only one side, it suggests a problem with the MFS. The flasher input to the MFS is connected in the MFS for the rear lights. Also, since the left brake lights and the park lamps work, it suggest that the ground is good to the left rear sockets is good (pin G).

 

Ya, except.

#1 - The MFS does not explain why the 3rd brake light flashes.
#2 - The OP PM'd me and he has jumpered the purple to the yellow to bypass the MFS and yet the left signal lights would not flash (but the 3rd brake light was flashing).

Both contradict the MFS as being the issue.

The info is contradictory for a car with domestic tail lights. That's why I asked if the car has Euro Tail lights, which have seperate brake bulbs and flasher bulbs which could help explain what's going on.

Peter

 

Fair enough

 

Hi the car does not have euro tail lights. It has the original G.M. lights. I just got the multimeter to try to help diagnose this problem so I might have made a mistake when I took the measurements. The instructions on it are kind of vague so I will read them again and re check the bulb sockets. I did check both cars at the same time so I don't know how I could get two such drastically different numbers I must have some how moved the dial. I also agree that now the problem seems to be somewhere else it the car but I am really stumped on where to look. As far as the front goes I saw the splice pack in the front of the car kind of on the passenger side a little and I was planing on checking them when the blinkers are fixed since it is just a marker light that I am having a problem with in the front the running/blinker lights in the front work fine.I already checked the splice pack in the back and took it apart and cleaned it. I work nights so that's why I didn't respond earlier. I usually get home at four or five in the morning. I will try anything that you guys think will help I am not afraid to take the car apart or try things. I was wondering since the third brake light flashes when I put on the left blinkers should I try to find all of the places that those two circuits run and see if there is any other place that they could meet or possibly ground out or short each othe somehow?

 

How about this. The left stop/flasher wire is yellow. So is the third brake light. Have they got swapped?

 

All of the wiring looks pretty much untouched. Everything I have taken apart still hes all of the factory clips and wire ties. You can tell it has never been apart. Where do you think is a possible place they could have been switched?. The only place I can think of is the back behind the bumper cover. I have checked all of those wires and cleaned the splice clip but I will re check them.

 

PM sent.

 

I would think at the rear. Get someone to sit in the car and do all the functions like braking with the turn signal on. With and without the lights on. All permutations. I think you will find that the third brake is working like the turn/stop and the turn/stop is working like the third brake. If that is the case, swap the wires and you are done.

 

Could be. I do agree with you that it'd have have to be at the back of the car since those 2 wires go through different connectors at the front. But, it appears both are yellow in the main harness running along the drivetrain too. Looking at the schematics, both of those wires go to the connector C400, which I would believe is the one at the back. Probably would be a good idea to look over the rear harness as much as possible. It comes out of the tunnel on the right side of the torque tube then goes above the trans and diff and then wraps down behind the diff and out towards both wheels. The plug for the rear lights is on the right rear at the back of the wheel well. Then, the harness goes back to the rear lights.

Peter

 

The OP just PM'd me.....he forgot one important piece of info. The third brake light flashes with the hazards. Since they just got the car, and it has done this since day one......it probably had a wiring repair, or been in an accident.....and some goofball mis spliced the wires.

 

Hey guys I think you are right. I am running out the door for work. Dad was back there telling me which lights were flashing he must not have seen the third brake light or not noticed. I am sorry for not catching it. I didn't see it until today. As soon as I get the car back I will trace the wires all of the way from the back to the front. The back wiring looks perfect so it must be a little further up the wire but if it's there I will find it. Thanks so much to everyone who helped us we appreciate it soooo much. I feel like at least know I have a pretty good idea where to look. I will let you know as soon as I get the car back

 

To bad you didn't find something at the back. That's the easy place to get to the harness.

You won't be able to get to the harness from the trans until it comes out behind the engine. you'd have to drop the drivetrain to get at it in the tunnel and pull the intake to get at it behind the engine. If the car does appear to have been apart then keep looking where it's visible for signs of repair work.

Peter

 

Yea I know. I am going to have the car up on a rack this weekend. The check engine light came on. I coded it out ant it's a P1810 code. T.F.P transmission fluid pressure switch. The code came up on the D.I.C and I cleared it hoping it was a glitch but now it threw the check engine light so dad can't smog the car. I know the guy knew about this also and forgot to mention it to my dad (Trust me I am going to address that issue also) I am going to go ahead and service the transmission when I replace the valve. I ordered the whole valve assembly with a new harness so hopefully that will fix the problem. All of the parts together were a $100.00 dollars plus the fluid and filter so it's not to much of an investment to eliminate that possibility. If it comes on again at least we know it's not that. I am pretty sure that's what it is. I have checked the wiring in the back all of the way until it goes through the frame under the car so it will be a good way for me to check the wiring more while it's up there and see if I can find anything. As I work on the car I am kinda getting attached to it. It just needs a little T.L.C and has been neglected and we are stuck with it now. I am just going to get it fixed one thing at a time. It runs well and drives well and everything on the inside works perfect so I guess it could be worse but it's bad enough.