Why do both rear turn signals blink when the right side is turned on?

[Earl43P]

You've proven you can use a multimeter.

Set it to ohms and measure the right rear lamp's ground(s) wires to a good ground.

It acts as if the right rear turn signal ground path is open.
That wil force the lamp to seek its ground through the parking lamp element of the lamp, which is shared with the left side (running lights).

By the way, the actual ground point for the tail and stop/turn lamps is under the hood on one of the inner fenders.

 

[Scrambler82]

Or... Add a temporary ground to the right side and see what happens.

The other directional switch... From the 89, did all of the lights acted the same ?
Did you happen to put the questionable one in the 89 and see what happens while it is in there ?
Did you put in any new grounds ?

There is only two things that tie all these light together, the ground system or directional multifunction switch, so if all of the grounds are good I would look not only at the switch AGAIN but also the wiring around it, the wiring in the steering column also and all of the connectors on the column.

I had a 68 Stang where the Fog Light Sw shorted out and caused the brake lights and the plate light to come on all the time. Everytime I stop somewhere for awhile I had to pull the battery so it wonuldn't go dead so stranger things have happened.

Ltr

 

[greaseyfingers]

Or... Add a temporary ground to the right side and see what happens.

The other directional switch... From the 89, did all of the lights acted the same ?
Did you happen to put the questionable one in the 89 and see what happens while it is in there ?
Did you put in any new grounds ?

There is only two things that tie all these light together, the ground system or directional multifunction switch, so if all of the grounds are good I would look not only at the switch AGAIN but also the wiring around it, the wiring in the steering column also and all of the connectors on the column.

I had a 68 Stang where the Fog Light Sw shorted out and caused the brake lights and the plate light to come on all the time. Everytime I stop somewhere for awhile I had to pull the battery so it wonuldn't go dead so stranger things have happened.

Ltr

I've already tried running a temporary good ground wire, right off the battery's negative post, all the way back to the brake light/turn signal socket's 3rd ground wire that goes into the tail light socket..

Even after doing this, the left side turn signal still continues to flash, when the right side turn signal switch is used for activating the right side turn signal light..

Even after installing a good working turn signal switch from my 89 Ranger, it still didn't correct my 90 Ranger's turn signal problem..

I'm not 100 percent sure, but last summer I think that I do recall putting my 90 Ranger's turn signal switch in my 89 Ranger, to see if it would work properly, and it did so without any problems, or issues that I'm having with using my 90 Ranger's right side turn signal light, that for some unknown reason, I haven't been able to figure out, yet, what is causing my 90 Ranger's rear turn signal lights to both flash, when the right side turn signal switch is used..

 

[greaseyfingers]

You've proven you can use a multimeter.

Set it to ohms and measure the right rear lamp's ground(s) wires to a good ground.

It acts as if the right rear turn signal ground path is open.
That wil force the lamp to seek its ground through the parking lamp element of the lamp, which is shared with the left side (running lights).

By the way, the actual ground point for the tail and stop/turn lamps is under the hood on one of the inner fenders.

You mentioned the actual ground point for the tail ans stop/turn lamps is under the hood on one of the inner fenders..

Are you talking about the actual steel fender itself, or the fender's inner fender well that looks like it's made from some other material that doesn't look like it's made from steel..

I'm going to try and locate the actual ground point for the tail and stop/turn lamps that's under the hood on one of the inner fenders, as you mentioned, and see if cleaning them will make any difference..

 

[Scrambler82]

I've already tried running a temporary good ground wire, right off the battery's negative post, all the way back to the brake light/turn signal socket's 3rd ground wire that goes into the tail light socket..

Even after doing this, the left side turn signal still continues to flash, when the right side turn signal switch is used for activating the right side turn signal light..

Even after installing a good working turn signal switch from my 89 Ranger, it still didn't correct my 90 Ranger's turn signal problem..

I'm not 100 percent sure, but last summer I think that I do recall putting my 90 Ranger's turn signal switch in my 89 Ranger, to see if it would work properly, and it did so without any problems, or issues that I'm having with using my 90 Ranger's right side turn signal light, that for some unknown reason, I haven't been able to figure out, yet, which is causing my 90 Ranger's left side turn signal light to flash, too ..

OK so you have all of the major components covered... now you need to trace all the wiring from the steering column to the rear lights.

 

[greaseyfingers]

OK so you have all of the major components covered... now you need to trace all the wiring from the steering column to the rear lights.

Another thing I noticed is that if I put on the right side blinker on my 90 Ranger, without the key in the ignition, and press the brake pedal..

The right front, passenger's side, turn signal bulb will light up, along with the right side turn signal indicator light that's on the dash, and the turn signal relay flasher will start clicking, but the neither the passenger side right front turn signal light, or the right side turn signal indicator light that's on the dash, don't flash when the brake pedal is being depressed and both the rear brake lights will stay on..

While the turn signal flasher relay is clicking, as explained.. When I turn the heater blower motor's switch on high, without the key on, as the lower speeds aren't working due to the heater blower motor's resistor needs replacing.. Each time the turn signal flasher clicks, the heater blower motor will start running during each clicking sound the flasher makes and then stop between each click..

Even though the heater blower motor's resistor needs replacing, I don't think that would have any affect on causing my 90 Ranger's turn signal problems, could it..

How would it be possible for any electrical current to be reaching the heater motor, as explained, when the ignition switch isn't even on, is beyond me..

The turn signal problem on my 90 Ranger is getting to be very annoying and frustrating, when I haven't been able to figure out a solution, yet, to whatever is causing it..

I hope someone reading this is able to figure out a solution to fixing my 90 Ranger's turn signal light problem, as I haven't been able to, so far..

 

[fordracing60]

Try Unplugging the connector for the rear lights. That will narrow down where to look for your bad ground.

 

[fordracing60]

Also clean up all your major grounds.

 

[greaseyfingers]

Try Unplugging the connector for the rear lights. That will narrow down where to look for your bad ground.

I found and cleaned the brake/tail/turn signal and parking light ground located on the driver's side inner steel fender..
It didn't help any, I'm still having the same problems..

I cleaned a ground located on the apron above the radiator, still no difference..

I cleaned a ground on the passenger side inner steel fender, still no difference..

I cleaned the battery posts and terminals, still no difference..

The only ground that I haven't cleaned, yet, that I know of, is on the end of the big ground wire cable that's located and bolted near the starter..
But, the starter is working good.. So, I'm assuming the stater's ground wire cable should be OK, shouldn't it.. Or, should I clean it, anyway..

When I unplugged the male/female connector that's near the rear bumper for the back tail/brake/turn signal lights..
All the symptoms were the same, as before, except there was no power going to the rear tail lights/brake lights/turn signal lights when this connector was unplugged..

After I plugged this connector back in by the rear bumper..
I unplugged the front connector that's located on the driver's side inner fender well, thats for the rear tail lights/brake lights/turn signals and parking lights..

I didn't have any symptoms of any problems happening, as before..
However, I didn't have any power going to the rear tail lights/brake lights/turn signals and parking lights, either, when this connector was unplugged..

So, do you think the problem is being caused somewhere in the length of wires that goes between these two connectors, that goes from the driver's side inner fender well back to the other connector that's near the rear bumper..

And, if so, is that correct length of wiring harness with the connector ends on it, still available to buy at an automotive parts store and what would it cost, and what would this particular wiring harness be called..

Or, what would the best way to find the bad wire in mine be to repair it, if none of the wires look obviously damaged from the outside for finding the bad wire to repair, if a new harness, of this type, is not currently available, anymore..

 

[fordracing60]

Sounds like tour prob is in the rear wiring. Unplug the harness in the back and take it off the truck. Remove the covering and check everything. It can be a pita but worth the effort. You will know what ya have back there.

 

[greaseyfingers]

I found and cleaned the brake/tail/turn signal and parking light ground located on the driver's side inner steel fender..
It didn't help any, I'm still having the same problems..

I cleaned a ground located on the apron above the radiator, still no difference..

I cleaned a ground on the passenger side inner steel fender, still no difference..

I cleaned the battery posts and terminals, still no difference..

The only ground that I haven't cleaned, yet, that I know of, is on the end of the big ground wire cable that's located and bolted near the starter..
But, the starter is working good.. So, I'm assuming the stater's ground wire cable should be OK, shouldn't it.. Or, should I clean it, anyway..

When I unplugged the male/female connector that's near the rear bumper for the back tail/brake/turn signal lights..
All the symptoms were the same, as before, except there was no power going to the rear tail lights/brake lights/turn signal lights when this connector was unplugged..

After I plugged this connector back in by the rear bumper..
I unplugged the front connector that's located on the driver's side inner fender well, thats for the rear tail lights/brake lights/turn signals and parking lights..

I didn't have any symptoms of any problems happening, as before..
However, I didn't have any power going to the rear tail lights/brake lights/turn signals and parking lights, either, when this connector was unplugged..

So, do you think the problem is being caused somewhere in the length of wires that goes between these two connectors, that goes from the driver's side inner fender well back to the other connector that's near the rear bumper..

And, if so, is that correct length of wiring harness with the connector ends on it, still available to buy at an automotive parts store and what would it cost, and what would this particular wiring harness be called..

Or, what would the best way to find the bad wire in mine be to repair it, if none of the wires look obviously damaged from the outside for finding the bad wire to repair, if a new harness, of this type, is not currently available, anymore..

After I sprayed some WD/40 on the sealed ends of the 5 wire connectors, it soaked in to where the wires go into the turn signals 5 wire connectors, that's on the driver's side fender well..

It started doing it, again, one of the problems has returned.. Maybe some corrosion loosened up by spraying WD/40 on the end of the connector, is crossing over to some of the 5 wire's inside contacts, as I noticed, again, that if I put on the right side blinker, without the key in the ignition, and press the brake pedal..

The right front, passenger's side, turn signal light and the right side turn signal indicator light on the dash, will light up and the turn signal flasher will start clicking, but the right front turn signal doesn't flash, while the brake pedal is being depressed and both the rear brake lights will stay on..

While the turn signal flasher is clicking, as explained.. When I turn the heater blower motor's switch on, without the key on.. Each time the turn signal flasher clicks, the heater blower motor will start up on each click the flasher makes and then stop between each click..

It does this, now, as explained, even when this 5 wire connector isn't plugged in..

When I plug this 5 wire connector together, on the driver's side, fender well, it continues to do it..

When I turn the ignition switch on, when the right side turn signal switch is on, both the rear turn signals continue to flash, until I put on the brakes..

Then both rear turn signals will stop flashing, and there will be just brake lights, as long as I'm holding the brake pedal down, but I don't have a right side rear turn signal light that will flash, either..

Should I just cut this 5 wire turn signal connector out of the turn signal wiring harness, and splice it together, and hope it solves my problems..

Are there 5 wire universal splice connectors available for doing this..

Does anyone have a diagram of all the wires going the to turn signal switch, to make sure they are all going to the correct terminals in the plug in connectors..

I'm almost tempted to buy a new after market turn signal switch on ebay, that I seen for less than $45.00, for seeing if that will solve my problem..

But, remembering when I tried putting my good working turn signal switch from my 89 Ranger into my 90 Ranger, it didn't solve my rear turn signal problem..

So, I'm still kind of doubtful that buying a new after market turn signal switch from ebay would solve my problem, either.. As maybe, it would be just wishful thinking to do so, and a waste of money..

What would you do if you were in this situation..

 

[enjr44]

I have gone through this thread twice. I think you can eliminate the turn sig sw. I also think you have been looking at this so long it is driving you nuts and your are running in circles.

I think you have a bad wire or wires that are causing cross talk. Maybe a connector that is connecting two wires together that should not be connected. Or a couple of wires touching each other (either bad insulation or bad connector. And it does not have to be in the rear of the truck.

I have attached the wiring diagrams (I think) for those circuits. If they don't upload send me a PM and I will email them to you. This problem can be fixed. It is just a matter of relaxing and taking you time to figure it out.

Ed

 

[enjr44]

Your Stated Problem and Conditions:
When turn-signal SW is in left turn position left front light blinks and left rear light blinks. Right front and right rear turn-signal lights are off. So everything appears normal and to be operating correctly.
When turn-signal SW in in right turn position the right front blinks and the right rear blinks correctly. However the left rear turn-signal light also blinks and it should not.
The bulbs and grounds have been checked and eliminated as possible causes of the malfunction. The turn-signal (multi-function) switch has been swapped with a known good SW
The Hazard lights are working correctly.

System Operation (using the diagrams in post # 42):
So if you follow the wiring diagram you will see that with the turn signal SW in the OFF position the both rear lights receive power from terminal 9 (LT GRN wire) when you press on the brake pedal. The left from terminal 10, with DK BLU/Wht wire, and the right from terminal 2, with BRN/YEL wire.

If you move the turn-signal SW to the left or right positions you disconnect the rear lights from terminal 9 and connect either (not both at the same time) the left rear or right rear light to the flasher through terminal 1 (LT BLU wire). The flasher starts cycling because it sees a high resistance ground through the front and rear turn-signal bulb filaments (some sort of electronic magic) that then causes the flasher relay to cycle.

So, the flasher then powers right or left turn-signal circuits inside the turn-signal SW and that light will begin flashing (not both at the same time).

The Hazard lights work the same way except all lights are connected to the flasher through terminal 4 and the brake SW power is NOT disconnected. So when you press on the brake pedal they stop flashing. The flasher is still cycling; but, you just can’t see it.

Troubleshooting
If someplace between the turn-signal SW and the rear turn-signal lights the DK BLU/WHT wire and the BRN/YEL wires were shorted together then both the left and right rear lights would flash when the turn-signal SW was in either the left or right position. You could not get it to malfunction only when the turn-signal SW was in the right position. So I think those circuits are good.

If however, the LT BLU wire from the flasher (on terminal 1) was shorted to the DK BLU/WHT wire (on terminal 10) someplace you would get this malfunction. The LT BLU wire supplies the power for the turn-signal lights so it could light the left light anytime the turn-signal SW was in either the left or right position (in the left position it would just appear normal).

You might also (IDK) get this condition if the RED/WHT wire (on terminal 4 ) was shorted to the DK BLU/WHT wire (on terminal 10) someplace. IDK because I don’t know if there is power on terminal 4 anytime the flasher is cycling. It wouldn’t normally matter because terminal 4 is not connected to anything inside the turn-signal SW when the Hazards are off.

Anyway, something to look at. Also, IDK if the diagrams are for your exact truck; but, they should be almost the same.
Ed

 

[greaseyfingers]

Your Stated Problem and Conditions:
When turn-signal SW is in left turn position left front light blinks and left rear light blinks. Right front and right rear turn-signal lights are off. So everything appears normal and to be operating correctly.
When turn-signal SW in in right turn position the right front blinks and the right rear blinks correctly. However the left rear turn-signal light also blinks and it should not.
The bulbs and grounds have been checked and eliminated as possible causes of the malfunction. The turn-signal (multi-function) switch has been swapped with a known good SW
The Hazard lights are working correctly.

System Operation (using the diagrams in post # 42):
So if you follow the wiring diagram you will see that with the turn signal SW in the OFF position the both rear lights receive power from terminal 9 (LT GRN wire) when you press on the brake pedal. The left from terminal 10, with DK BLU/Wht wire, and the right from terminal 2, with BRN/YEL wire.

If you move the turn-signal SW to the left or right positions you disconnect the rear lights from terminal 9 and connect either (not both at the same time) the left rear or right rear light to the flasher through terminal 1 (LT BLU wire). The flasher starts cycling because it sees a high resistance ground through the front and rear turn-signal bulb filaments (some sort of electronic magic) that then causes the flasher relay to cycle.

So, the flasher then powers right or left turn-signal circuits inside the turn-signal SW and that light will begin flashing (not both at the same time).

The Hazard lights work the same way except all lights are connected to the flasher through terminal 4 and the brake SW power is NOT disconnected. So when you press on the brake pedal they stop flashing. The flasher is still cycling; but, you just can’t see it.

Troubleshooting
If someplace between the turn-signal SW and the rear turn-signal lights the DK BLU/WHT wire and the BRN/YEL wires were shorted together then both the left and right rear lights would flash when the turn-signal SW was in either the left or right position. You could not get it to malfunction only when the turn-signal SW was in the right position. So I think those circuits are good.

If however, the LT BLU wire from the flasher (on terminal 1) was shorted to the DK BLU/WHT wire (on terminal 10) someplace you would get this malfunction. The LT BLU wire supplies the power for the turn-signal lights so it could light the left light anytime the turn-signal SW was in either the left or right position (in the left position it would just appear normal).

You might also (IDK) get this condition if the RED/WHT wire (on terminal 4 ) was shorted to the DK BLU/WHT wire (on terminal 10) someplace. IDK because I don’t know if there is power on terminal 4 anytime the flasher is cycling. It wouldn’t normally matter because terminal 4 is not connected to anything inside the turn-signal SW when the Hazards are off.

Anyway, something to look at. Also, IDK if the diagrams are for your exact truck; but, they should be almost the same.
Ed

That sounds like a good probability of where the problem is, as you said ~~ "If however, the LT BLU wire from the flasher (on terminal 1) was shorted to the DK BLU/WHT wire (on terminal 10) someplace you would get this malfunction. The LT BLU wire supplies the power for the turn-signal lights so it could light the left light anytime the turn-signal SW was in either the left or right position (in the left position it would just appear normal)."

Now I'll just have to try and find the location in the wiring where it's doing that at, somehow..

Thanks for sending the Attached File wiring diagrams for those circuits.

What would be the easiest and fastest way to find the problem spot in this area of the wiring..

Do you have any suggestions, or advice, in that regard..

 

[enjr44]

This is bigger than the two rear lights flashing at the same time.

Problem one: Both tail lights flash when the turn-signal is put in the right turn position.

Problem two: The right front, passenger's side, turn signal light and the right side turn signal indicator light on the dash, will light up and the turn signal flasher will start clicking, but the right front turn signal doesn't flash, while the brake pedal is being depressed and both the rear brake lights will stay on.

Problem three: While the turn signal flasher is clicking, as explained. When I turn the heater blower motor's switch on, without the key on. Each time the turn signal flasher clicks, the heater blower motor will start up on each click the flasher makes and then stop between each click.

Well, as you have said, you have more than one problem and all of them are on the left side of the cab between the multi-function SW connector and the under the dash fuse panel (or someplace in the area). THAT IS IF THE MULTI-FUNCTION SW IS GOOD (you have said that you have swapped it with a known good one). You are probably right about that because of problem three. I do not know of a way for that to happen from a malfunction inside the multi-function SW (turn-signal sw).

There is something down (under) there in that great gob of wires connecting all of these problems together.

Problem one - We have already discussed. It could be caused if the LT BLU wire from the flasher (on terminal 1) was shorted to the DK BLU/WHT wire (on terminal 10.

Problem two - Can be caused if terminal 9 (LT GRN) wire was shorted to terminal 5 (WHT/LT BLU) wire. When you press the brake pedal the short would connect power to those lights. It would take ANOTHER short to terminal 1 to make the flasher cycle. However nothing would flash because of the steady 12 volts coming from terminal 9.

Problem three - Is the one that makes me think there are shorted wires between the under-dash fuse panel and the multi-function SW. That is one great mass of wiring. I am sure the blower motor control wires are in there someplace.

I think I would remove the front pass seat so I could lie on my back and work on it. Next, I would then remove the negative battery terminal. I would then start looking at the wiring, pulling the wrappings off and inspecting the wires one by one. You may have to take dash panels off to get to all of it and trace each wire from end to end.

Look for physical damage first. Look at the connectors. Separate the wires looking for damage. Something that may have been done by a PO that is now causing a problem. I once found a broken drill bit that had been run through a wire harness on a HC-130. It had been flying that way for some time before it finally started causing all sorts of weird problems.

Anyway, that is the area I would look at. You have more than one thing that doesn’t work correctly and they all point to the wiring under the dash on the left side.

Best of luck, Ed