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A. Penland
A. Penland, Ford Senior Master Technician, ASE
Category: Ford
Satisfied Customers: 6563
Experience:  ASE Master Certified, ASE Advanced Gasoline Engine Performance
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Brake lights and turn signals not working, what does the

Customer Question

Brake lights and turn signals not working
JA: Have you checked the brake fluid? How's the level and when was it last changed?
Customer: what does the fluid level have to do to turn signals
JA: What is the model/year of your Ford?
Customer: 2000 F-350
JA: Are you fixing your F350 yourself? What have you tried so far?
Customer: Yes, checked fuses
JA: Anything else you want the mechanic to know before I connect you?
Customer: no
Submitted: 10 months ago.
Category: Ford
Customer: replied 10 months ago.
You need to reply to email***@******.***
Expert:  A. Penland replied 10 months ago.

Is the cab/third brake light inop also?
Do you have a digital multi meter or test light to do a few electrical tests?

Customer: replied 10 months ago.
third light is out as well
Yes I can do a few tests,if explained in detail
Customer: replied 10 months ago.
One item that I forgot to tell you...Before I lost turn signals and brake lights, when I applied the brakes or my left turn signal, the lights in the dash would come on. Almost like the dash lights were connected to the turn and brake light circuit
Expert:  A. Penland replied 10 months ago.

The problem may be caused by the turn signal/wiper switch we call the multifunction switch. But lets do a couple electrical checks to make sure. First go to the brake light switch and check for power solid light green wire with the switch plugged and step on and off the brake pedal. See if that wire has power when you step on the brake pedal.

Customer: replied 10 months ago.
Ok, already replaced the multi function switch no change.
still check the brake light switch?
Customer: replied 10 months ago.
key on, brake applied, power to solid green wire connected to brake switch on brake pedal
Expert:  A. Penland replied 10 months ago.

Ok. You will need to take the trim panels off the steering column and check the wiring connectors at the turn signal switch/wiper switch. We have seen the wiring pull loose from the connector for the switch. Check for power on the LIGHT GREEN wire at the turn signal switch. The power from the left and right brake lights goes through the switch and the power for the third brake light goes straight from the brake light switch to the third brake light. You may want to check the bulbs in the third brake light.

Customer: replied 10 months ago.
tested for power on light green solid wire attached to multifunction switch; no power when connected and no power when I removed the connector and tested from the front of the connector; key still in the on position
Customer: replied 10 months ago.
Good news, brake light bulb was blown. swapped bulbs with box lights.
Customer: replied 10 months ago.
High mount brake light bulb
Expert:  A. Penland replied 10 months ago.

Make sure you are on the correct wire. Below is a picture of the connector. The wire is in pin #511.

Customer: replied 10 months ago.
No power on pin#511;power on pin#44 and Pin#385
Expert:  A. Penland replied 10 months ago.

Unplug the flasher relay. It is in a black relay box under the dash. You should not have power on those two wires unless the turn signals are on.

Customer: replied 10 months ago.
no sure what I am looking for. Is the relay in the fuse panel? Looking for a round flasher relay under dash, not able to locate it. Can you send a picture of its location?
Customer: replied 10 months ago.
ok think I located relay under dash, two relays together; one black one blue. Removed blue relay; Tested for power, only terminal #2 has power, when key on turn signals activated.
Expert:  A. Penland replied 10 months ago.

Do you have a trailer harness on the rear of the vehicle?

Customer: replied 10 months ago.
Expert:  A. Penland replied 10 months ago.

Is it factory or added on?

Customer: replied 10 months ago.
add on / connected to existing harness
Customer: replied 10 months ago.
or possibly another harness not sure
Expert:  A. Penland replied 10 months ago.

You may want to inspect the wiring. You should not have power on pin #2 with the relay removed.

Customer: replied 10 months ago.
what am I checking for
Expert:  A. Penland replied 10 months ago.

Wait. Do you still have power on pin #2 with the turn signal switch unplugged?

Customer: replied 10 months ago.
with connector 230b disconnected I still have power to Pin#2
Expert:  A. Penland replied 10 months ago.

Check the right front turn signal bulb and socket. Pin #2 goes to the right front turn signal. You have a short to power on the right front.

Customer: replied 10 months ago.
ok I will check it in the morning, can I contact you back on this chat line?
Expert:  A. Penland replied 10 months ago.

Just reply back on this post when you are ready. I will be on line tomorrow afternoon.

Customer: replied 10 months ago.
I checked the front right turn signal socket and wiring, not bear wires or signs of chafing on the harness. There is a wire spliced in for the plow lights which I removed. Still not turn signals; check for power on Pin#511 no power.Note: Earlier I mentioned that when I apply the brakes, my dash lights & taillights come on and radio dims ( I assume because the running light circuit is being activated)
Expert:  A. Penland replied 10 months ago.

#511 gets power straight from the brake light switch when the brake pedal is depressed. And since you have power at the switch, the wire is broken between the brake switch and the multifunction switch. But I wonder what else is wired into the light circuit that would cause the draw and cause the lights to dim. Either a large load or a short with high resistance causing this problem.

Customer: replied 10 months ago.
should I do a lay over from the solid green wire at the brake switch to the solid green wire at the multifunction switch?
Customer: replied 10 months ago.
There is a trailer brake controller which I will disconnect and retest.
Expert:  A. Penland replied 10 months ago.

Try that. Do no splice it is, just run a jumper from the brake switch to the turn signal switch. Also, disconnect the brake controller and look under the dash for any strange wiring splices.

Customer: replied 10 months ago.
Ok we are making progress. The brake lights are working now. The brake controller has been eliminated. No turn signals (the flasher was reinstalled); the dash lights still come on when the brake pedal is depressed.
Expert:  A. Penland replied 10 months ago.

So all you did was unplug the controller?

Customer: replied 10 months ago.
No, I did a layover plus disconnect the controller
Expert:  A. Penland replied 10 months ago.

Follow the harness down the column and make sure it is not pinched between the column and the metal dash brace.

Customer: replied 10 months ago.
Is this to correct the turn signals?
Expert:  A. Penland replied 10 months ago.

The harness may be cut somewhere down the steering column.

Customer: replied 10 months ago.
OK, removed the harness from the multifunction switch out of the steering column, no breaks or chafing on wires, inspected harness to where the harness passes through the firewall, no pinched, broken or chafed wires.Still have brakes lights; no turn signals and running lights (interior and exterior) come on when brake pedal is depressed
Expert:  A. Penland replied 10 months ago.

Are you still getting power on pin #2 at the turn signal switch?
Also check pins #5 an #9.

Customer: replied 10 months ago.
This is the connector attached to the multifunction switch? C230b
Expert:  A. Penland replied 10 months ago.

Correct.

Customer: replied 10 months ago.
I have power on #511 when the brake pedal is depressed
The test light is faint (not bright) on #44 & #385
Power on #9 when headlights are turned on
Expert:  A. Penland replied 10 months ago.

There is something shorting the system out. You will need to go under the vehicle and follow the harness to the rear tail lights.

Customer: replied 10 months ago.
Ok, that will have to be done tomorrow. Thanks for your help this far, I will reply back once I have checked out the harness
Expert:  A. Penland replied 10 months ago.

This may end up requiring a hands on electrical mechanic to find the problem. But keep me informed.