A month ago my car dash started flickering when I would turn my lights on. My blinker lights would also both flash like my hazard lights were on, not allowing me to use my front blinkers. I pulled the left and right running light relays and the dash acted normal, with no front blinkers. My heater and ac do not blow now either. Last night my brake fuse blew, and service traction control came on. Rear blinkers went out too. I replaced the fuse and as soon as I pressed the brake pedal the fuse blew again. I don't know anything about electrical. Where should I start looking to diagnose this issue?

 

C5 pull codes before shutdown

If you pull your codes after you turn the ignition OFF almost all will show H. Clear everything and go for a drive and then pull the again BEFORE you turn the ignition OFF.

 

C1291 is only TCS code given. Unplugged rear harness and pulled the ABS fuse and replaced the stop/hazard fuse and turned the hazard lights on with the key to on with the car off. Also have brake switch unplugged. Fuse still blew.

 

OK, lots of weird things going on. Let's not worry about the TCS issue, radio, and HVAC right now. For the fuse to blow you have a short or very high current load going on.

Recommend you PM me with your number so we can talk. All I can say is that when you remove the DRL relays the front turn signals will not work. That is normal.

Also when you talk about fuses you should also identify what fuse number and in what fuse box so we are clear.


Mr. Sam

 

Hey Sam another very interesting can of worms... please post a summary again for those of us wanting to learn more about these tricky electrical systems... Thanks Steve

 

Sam i am going to get up with you shortly. i am going to post a general summary.

 

1. Ordered new hazard switch
2. Removed, disassembled, assessed, "repaired", reassembled and re attached the multifunction switch.
3. New brake switch, both assemblies.

My problem is - when I use my brakes, turn signal, or blinker SITTING STILL with the car off, they are fine. Start it up, and try to test drive I blow fuse 8 and 15. I have followed my factory service manual to a T, but I am no electrician so there are some parts unclear to me.

I am diagnosing from Hazard Lamps Inoperative, as neither blinker is either, when jumping from c215 connector b to j with the ignition 'on' there are no tail lights, but I have replaced the hazard switch regardless. after testing the multifunction switch connector c209, for 0-2 ohms in circuit 27 terminal a to connecter c215 terminal j i get 0.5, in specified values so i go to the next step which is circuit 27 (a) to (b) and (c) for 0-2 ohms, back probing with the switch connected in neutral position, i get (b)0.2 and (c) 0.3. it tells me to go to the next step which is repair high resistance or open condition in circuit 18 or 19, if ok replace inoperative bulbs. for kicks i turned the switch left and right and measured the ohms from b and c in each and with each, left on, right measured 0, right on left measured 0. it then sends me to replace multifunction switch, hazard switch, and after those two, high resistance or open in circuit 27, (a). all of which test good. after removing the fuse from 8 and testing (a) to a ground the resistance was 15.00 Mohm, which i believe to be higher than 0.5 specified, it says repair short in circuit 140, if no then 14 and 15, if no 17 and 27, and if no 18 and 19. this car has a lot of wires!! i'm stumped! help please!

 

"My problem is - when I use my brakes, turn signal, or blinker SITTING STILL with the car off, they are fine."

So you are saying these all actually work when the ignition is OFF? Would not expect Turn signals to work since the Flasher and circuits should not be powered with ignition OFF.

Fuse 15 provides power for Turn signals when the ignition is only HOT in ON or START. Provides power to nothing else, just the Hazard switch Flasher to activate the Turn signals.

Fuse 8 provides power for using the Hazards function and is ALWAYS HOT. But it also provides power to the Stop lamp switch. That way the brake lights can work when the ignition is OFF. If the Hazards are ON then the brake lights are cut out of the circuit and can't be used.

Do you know if both fuses blew due to just using the brakes or Turn signals or some combination? Not interested in having you do that again. I would rather check some things first, I don't want to blow a fuse just for diagnostics.

Got your number and will call later.

I don't know what Mohm means, milliohms or megaohms?


Mr. Sam

 

 

I am not sure either, it is a Fluke DMM and it reads in k and m sometimes. I am sorry I missed your call, I was still in bed. Now that I am up and moving around I'll return it soon. I mean sitting still with the key in the on position with the car off. One and the other BOTH blow both fuses. however i did notice that when they blow the right side blinker is dim and when it pulsates the entire MPH and corvette symbol lights do too.

 

With the Fluke Mohm would mean million ohms. That would be used for measuring a very high resistance.

Will call you later.


Mr. Sam

 

I think the issue is with your MF switch. I think there is an internal short you didn't see when you cleaned the contacts.

I tried to follow what you had done with diagnostics but did not have enough detail in what you said and could not find apparently what you did when I looked at 2 different FSM years.

Fuse 8 only provides power to the brake lights unless you turn on the Hazards.

Fuse 15 is only for the turn signals.

Both of these circuits go thru the MF.

The fact that you have both turn signal indications means power is going to both turn signal circuits where the design only allows one unless you have the Hazards on..

You may even be pulling some power into the light circuits controlled by the MF switch.

I had to ask myself why is it OK when the engine is OFF? There are no circuits that run thru the MF related to having the engine run. However, when the engine is running the circuit voltage will be about 14.2 and not 12.6. That increase in voltage apparently is enough to cause the short circuits to occur. Lightning does not occur until there is adequate potential.

I will be glad to look over your info but I need more specifics or the year you got it from.


Mr. Sam

 

are there contacts other than the ones that move when the turn signals are activated? i'm sorry if my information was confusing - the left and right turn signals, the hazard lights, and brakes all blow fuses, not just one or the other, or a combination. however i can remove the brake switch and the turn signals/hazard lights still blow said fuses.

when i activate the left turn signal, only the left activates. and vice versa, in neutral position it tests .3 on left and right wires. when one is activated the resistance becomes infinite in the opposite.

 

Fuse 8 should have no way to blow if the brake switch is removed and you are not using the Hazards. It is isolated with no where to provide power. If it is bowing you have a serious wiring issue somewhere.

I can't evaluate your above info since I have no idea where you measured.

 

In the connector harness to the mfs. A to b and a to c. But for the sake of it I went ahead and ordered another mfs

 

after another test the turn signals only blow fuse 15. no brake sensor attached.

 

I would think you have a short to ground or a cross connection to other circuits. Most likely in the MF switch or some where between it and the lights.

I would be testing the MF switch for continuity between the turn signal circuits and the other light circuits. Would not take much for a short to the HLs to blow that fuse.

If you need the connector pin outs let me now.


Mr. Sam

 

new multifunction switch arrived today, plugged in and since i bought hazard switch i got a brake sensor too. everything works fine! i was so happy i even fixed my hvac! thank you so much for your help

 

 

Yeah my money was on the MF switch. Glad you wrestled it to the ground.


Mr. Sam