Hi this is gonna be a question for one of those electrical guys. I am pretty much stumped at this point. Here is what we have. The car is a 2002 the left side blinkers are what we are having a problem with. I will try to describe it the best that I can. The running lights and tail lights work perfectly. The brake lights work perfectly as well as the headlights. the right side blinkers work fine.the left side front marker light won't work but the rest all do changed the bulb and then checked the bulb socket for power and it has none. I am not sure if the marker light has anything to do with the blinker problems but it is on the same side so I thought I would mention it. When you turn on the left side blinkers the indicator light flashes quickly on the dash. The front left running light /blinker light flashes quickly the left rear tail lights do nothing but the third brake light flashes on and off. I have run all of the codes and all I have is a p1638 and a p1637 which is a charging system fault and as far as I know has nothing to do with the blinkers. I cleared those codes and will have to figure them out after we get the blinkers to work. I have already checked all of the wires I could find and replaces all of the bulbs. Not sure about the history of this problem this is the way we got the car. I know Bill Curlee and some of the other guys are knowledgeable about the C5"S electrical issues so I am hoping someone can help me and my dad figure this thing out. Thanks

 

Are you saying both front and rear markers don't work on the left side, or only the left front?

 

Just the front left all other marker lights tail lights brake lights and headlights are working. also turned on four way flashers and the fronts work on both sides but but on the back only the right works the lefts do nothing

 

Ok. Based on your description here's what we know:

1) The ground to the LF park/turn signal lamp is good, because the lamp flashes with the harzards on.

2) The wiring between the left DRL relay, and LF park/turn signal receptacle is good....again.....because the lamp flashes with the hazards.

3) The wiring between the MFS, and the left rear turn signal/brake lamps is good.....because brake lights function normally.


The output of the flasher is bussed together in the MFS for the following:

Rear turn signals, rear hazards,and Front turn signals.


There are separate outputs(from the flasher) to the front hazards(do not go throught the MFS).


Starting to sound like you have a funky MFS. I would use a meter and the schematic below, to isolate, so you can be sure. As fars as left marker, if all the other markers work, then the issue is isolated to the left wiring, or receptacle.

 

Thanks a lot for the information. I am going to try to take a look at the switch. I am not very good with schematics or electrical issues so I didn't see what you are talking about when I looked at them before. Honestly they really confuse me. The way you described it makes sense. I still don't understand why the third brake light goes on and off when I turn on the left blinker switch. I have a multimeter but I am not very good with it but I am going see what I can figure out. I guess it will be a good time to learn. Thanks again for your help. I will post my results

 

I would agree that if the front lights are all working correctly except for the one marker than it's likely in the wiring harness for that marker and I would also suspect the power and not the ground. However, double check that the signal flashing is as bright as the other side. A dull signal could actually be the marker filament flashing and that would happen if the ground was bad.

It does sound like the left rear has a ground problem. Especially when you say the 3rd brake light flashes with the left turn signal on. I'd have to see the schematics (which I don't have at the moment) to know what is connected on the left rear ground. But, if it was the MFS back-feeding the third brake light then the right side should be flashing too.

FYI, it also seems to me that the turn signal switch diagram above is wrong. For example, in the left position both the flasher and brake switch are hooked to the yellow wire but the dk green wire is left unconnected. It should be the flasher or the brake switch connected to the yellow wire, not both at once.

Peter

 

......true, making the assumption, that all the contacts move the same direction.

 

I was thinking it was a ground also but then I was confused because I have brake lights and tail lights and I am not sure if the brake light circuit and the blinker light/four way circuit use the same ground. Both front running lights are bright and blink the same when the four ways are on. I am not even sure where the left blinker circuit ground is. I have to take the steering wheel of to get to the blinker switch to check it out according to the manual so I need to get a puller to get the wheel off before I can try to check out the switch

 

Ok. Like I explained in post #4, you already know the ground to the left front turn signal bulb is good, because they flash with the hazards. I would troubleshoot one issue at a time, so start with the front. It is not necessary to pull the steering wheel, to access the connector for the MFS.

http://forums.corvetteforum.com/c5-t...-a-how-to.html

Start with verifying you do not have 12 volts to the turn signal bulbs, and go from there.

 

Thank you very much for the write up I appreciate you trying to walk me through this thing. I am going to go outside and take it apart tonight.I was referring to the ground for the left rear blinkers. Like you said I already know the front has a ground was just wondering if the left rear blinker and left rear brake light circuit used the same ground.

 

Yes.

 

Ok I got to the turn signal switch. I disconnected all if the wires and checked them. They all look fine. and the connectors all look clean. I turned the blinker on and moved the wires and the connectors around to see if it was a bad connection but it made no difference from what I can tell from the Schematic the left rear blinker is the yellow wire...I think. I am not sure how I should go about checking the switch for a problem. Or if I should try to jump the two wires and see if the blinkers will work if I bypass the switch. I think it's the dark green which I think is a ground but there are so many I am not sure and I don't want to cause any damage by jumping the wrong wire or testing the switch the wrong way...any help would be appreciated

 

The whole point in accessing the switch, is to take resistance measurements. Do you have a meter?

 

 

Yes I do. I just bought it yesterday so I will do my best to understand what you tell me to do

 

The pin assignments, correspond to the connector pinout above. Also note that the pins correspond with a wire color.

You need to determine if you can read through the switch itself. Separate the two connectors, and take your reading from the plug connected to the switch. With the switch in the "left turn" position, test the following resistance:

You should read close to zero ohms. Red lead will stay on pin D, black lead will test pins G and C.

Red lead from meter: pin D (purple wire)


Black from meter: pin C (yellow wire) ; pin G (light blue wire)

 

Hi just tested both leads. Red on D purple wire and black on G and C light blue wire and yellow wire. read 0.02 to 0.00 on both...so I am guessing that part of the switch is good?

 

On the front, You say both fronts flash as bright which then means it's most likely the power wire to the running light bulb. You're talking the big bulb and not the little one in the side of the light, correct?

On the rear, the turn signal and the brake use the same filament in the bulb. You say you have the correct brake lights but no turn signal. Yet, you also say you have a flashing 3rd brake light. The first points to the multifunction switch but the second points to a bad ground. The 3rd brake light gets it's power ahead of both the hazard and MFS so it should not be affected by either. If the MFS screwed up and back-fed the flasher power into the brake light circuit then all the rear lights should flash. So, to me, you seem to be decribing 2 issues.

Anyways, the purple wire is from the flasher and the yellow wire goes to the left rear signal/brake bulbs. A simple test is to just jumper from the purple to the yellow and see what happens (key-on of course). The left rear should flash rapidly. You could also jumper constant power into the yellow wire and check-out the rear lights.

You could pull a tail light out and confirm which filament is working during the braking and running lights. The fine filament (longer too) is the running light and the heavy filament (shorter too) is the brake/turn.

Peter

 

Yes. Now flip the lever to the right turn position, and the resistance should read open.

I was hoping you followed my advice in post #9, and had already checked for 12 volts at the bulb connectors.

 

checked it with the blinker on right with same results. Jumped from yellow to purple and the third brake light flashed rapidly but the left tail lights did not turn on. As far as checking the bulb voltage am I sorry I misunderstood what you were saying. I checked the voltage on the left rear with just the headlights and tail light on and it showed 25.7 volts now I am really confused battery shows 12.4 volts