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

[greaseyfingers]

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

Your comprehension of this complex electrical problem, and good advice for trouble shooting and problem solving are very helpful..

 

[enjr44]

It is called sneak circuit analysis and comes from many years of trying to figure out why highly modified recon aircraft do some of the weird things they do. They had wiring that didn't go where it used to or should, systems that had been added for special reasons, and so on. That caused things to happen when they shouldn't and things not happen when they should. That could really shake up a pilot. It was my job to fix it.

Ed

 

[Scrambler82]

Did you replace any of the bulbs... Are they installed correctly ?

 

[greaseyfingers]

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

I took a pretty close look, this afternoon, at all of wires that on the back side of the fuse panel that's under the dash and all of the wires going to the turn signal switch harness connectors on the turn signal switch..

I couldn't see anything obviously wrong with any of these accessable wires on the back side of the under dash's fuse panel, or the harness connecting wires at the turn signal switch..

I didn't have time to follow the individual wires through the mass of all the wrapped up wires, as I was hoping to find something obviously wrong, where, maybe, I wouldn't have to do that..

The after market radio that's installed in the 90 Ranger is wired into some of the wires from all of the wires the factory's stock radio connector has been cut off from and a number of these loose wires are just laying inside the dash, behind the after market radio..

Two of the four wires that are suppose to be connected to the heater blower motor's resistor aren't connected to it, so the heater blower motor only works on high..

Even with these two issues, as mentioned, all the tail lights on the 90 Ranger used to work fine, before..

So, I don't think they are what's causing the problem, now..

 

[greaseyfingers]

Did you replace any of the bulbs... Are they installed correctly ?

I have already tried replacing the rear tail light bulbs, with new #1157 bulbs and double checked to make sure that they were all installed correctly, as I know that can cause problems if they aren't..

 

[greaseyfingers]

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

Would it any easier to disconnect the wires that are causing the problem, and install new wires, without having to unwrap the whole mass of wires under the dash, in that great gob of wires connecting all of these problems together..

Then, I woulnd't have to try seperating and inspect each wire separately, from end to end, for trying to find the wires that are causing the problem..

If this could be done, which wires would I need to disconnect from their source and replace..

Do you think this entire problem was, maybe, caused by running the heater's blower motor on high too much, being the blower motor resistor wasn't working, and possibly caused the heater's blower motor power source wire to overheat and melt through the wire's insulation and fused several other wires together in the process..

 

[greaseyfingers]

Filament in one of the bulbs has broken and fallen onto the other filament. This makes the blinking cross over to the other side via the parking light circuit.

Either replace the front turn signal/parking light bulbs and the rear turn/brake/parking bulbs or remove and inspect them all till you find the bad one.

Bad ground do cause weird things to happen, verify all grounds.

Charles

When I pulled out the front left and right turn signals bulb sockets from the front turn signal lense assembly..

I just noticed that with the ignition key on, when I turn on the right turn signal switch for the right side, both elements in that bulb will flash..

Then, when I turn on the the turn signal switch for the left side, both the elements in that bulb will flash, also..

The double elements in both front turn signal bulbs are intact and not touching each other, either..

What would be causing this to happen, as explained..

Could this, some how, be related to causing both the rear turn signals to shart flashing when the turn signal switch for the right side is turned on..

Do you think one, or both of the front turn signal light sockets, are shorting out on the inside, some how, and causing the current to cross over..

 

[greaseyfingers]

When I pulled out the front left and right turn signals bulb sockets from the front turn signal lense assembly..

I just noticed that with the ignition key on, when I turn on the right turn signal switch for the right side, both elements in that bulb will flash..

Then, when I turn on the the turn signal switch for the left side, both the elements in that bulb will flash, also..

The double elements in both front turn signal bulbs are intact and not touching each other, either..

What would be causing this to happen, as explained..

Could this, some how, be related to causing both the rear turn signals to shart flashing when the turn signal switch for the right side is turned on..

Do you think one, or both of the front turn signal light sockets, are shorting out on the inside, some how, and causing the current to cross over..

Yesterday, when I tested the passenger side front turn signal socket with the ohm meter's probe on the ground inside the socket and probed one of socket's power terminals, I got less than 1 ohm..

When I tested the passenger side front turn signal socket with the ohm meter's probe on the ground inside the socket and probed the socket's second power terminal, I got 5.2 ohms..

When I probed both the power terminals inside the passenger side front turn signal socket, at the same time, I got 5.2 ohms..

After using the same test procedure on the driver's side front turn signal socket, the results were almost the same, except I got 5.4 ohms, instead, on the same terminals on this turn signal socket, as when I tested the other one..

The ohm meter test results were the same on both front turn signal sockets, whether the turn signal switch wiring harness connectors were connected, or disconnected from the turn signal switch..

So, would this indicate that the both front turn signal sockets are bad, or does it indicate something else..

And could this be causing both my Ranger's rear turn signal lights to flash when I use the right turn signal position on the switch..

 

[GentleRF]

I'd check the resistance with the bulbs out on both ends. That way you can figure out wher things are. Now if you have the right bulb in on the rear and you are reading a lower resistance on one and not the other contact, it sounds like a short in the wiring somewhere. When you make this test, make sure the right rear bulb is the only one in. Do the same test for the left. It may not show you where, but it will give you an idea of where to look next. I've had to check every wire from the back to inside the cab a number of times on various vehicles to find shorts or opens in circuits. I have that problem now on a Vanagon for the power windows as well as the heater.

 

[enjr44]

Do an Ohms check between the left and right turn signal lamp contacts. There should be nothing, nada, (infinity - very high resistance) between them. Those two wires are not connected together anywhere. No place . . . . No where . . . .

They are completely separate from the multifunction switch to the bulbs. Unless you have a trailer connector, they run straight to the bulb contacts.

If you get a low resistance reading, take the connector off the multifunction switch and do the test again. If you now get infinity, your problem is inside the switch. If you don't, I am guessing you have a short between the wires going to the back of the truck. Shorts in a wire bundle can cause really weird problems. There are license plate lights, and tail lights and turn signal lights.

Now do the right side and see if you get different readings. You should because you said that side works correctly when you are doing a left turn.

Oh and take the lamp out of the third stop light (high mount) and see what happens, it shouldn't change anything; but, ....

 

[greaseyfingers]

I'd check the resistance with the bulbs out on both ends. That way you can figure out wher things are. Now if you have the right bulb in on the rear and you are reading a lower resistance on one and not the other contact, it sounds like a short in the wiring somewhere. When you make this test, make sure the right rear bulb is the only one in. Do the same test for the left. It may not show you where, but it will give you an idea of where to look next. I've had to check every wire from the back to inside the cab a number of times on various vehicles to find shorts or opens in circuits. I have that problem now on a Vanagon for the power windows as well as the heater.

To check the turn signal socket's resistance, do I use the ohm meter for probing the turn signals light socket's inside ground connection, and probe each of the socket's inside power terminals, seperately, for seeing what the ohms are..

Or, should I probe both of the turn signals light socket's inside power terminals, at the same time, for seeing what the ohms are..

 

[greaseyfingers]

Do an Ohms check between the left and right turn signal lamp contacts. There should be nothing, nada, (infinity - very high resistance) between them. Those two wires are not connected together anywhere. No place . . . . No where . . . .

They are completely separate from the multifunction switch to the bulbs. Unless you have a trailer connector, they run straight to the bulb contacts.

If you get a low resistance reading, take the connector off the multifunction switch and do the test again. If you now get infinity, your problem is inside the switch. If you don't, I am guessing you have a short between the wires going to the back of the truck. Shorts in a wire bundle can cause really weird problems. There are license plate lights, and tail lights and turn signal lights.

Now do the right side and see if you get different readings. You should because you said that side works correctly when you are doing a left turn.

Oh and take the lamp out of the third stop light (high mount) and see what happens, it shouldn't change anything; but, ....

Can you explain how to do this Ohms check between the left and right turn signal lamp contacts, so it will get done correctly..

And what should the Ohms be if it is good, or bad..

 

[enjr44]

Can you explain how to do this Ohms check between the left and right turn signal lamp contacts, so it will get done correctly..

And what should the Ohms be if it is good, or bad..

Put the meter on the 200 ohms range (unless it is a self-ranging meter). When the meter is on and you touch the two probes together you will get something like zero ohms (the meter could read some resistance through the meter leads, but it should be very lowf ). When you move them apart you will get a reading of infinity (or nothing).

Make sure the turn signal switch is in the off position.

Now, put one of the probes on the left turn signal bulb contact and the other on the right turn signal bulb contact. If your meter leads are too short, you will have to use a jumper wire to make them longer. You should get the same reading as if the meter was NOT connected to anything.

If you get a lower reading that means the wires are connected together someplace. It probably will be a lot lower, just a few ohms or so; but, you really can't tell because you don't know what type of short you have. It could be what is known as a high resistance short.

You see, you are using a battery inside the meter to see if the wires are connected (they should not be) together someplace. The battery in the meter sends out say 5 volts (not all meters are the same) through one of the meter leads and the meter reads how much of it gets back to the meter through the other lead and then displays it as ohms.

Like I said before, if you get a low ohms reading, take the connector off the multifunction sw and do it again. If you get the same readings (or close) it is the wires getting together someplace. If you now get nothing, it should be the switch. I would try a known good switch if you can.

With a known good sw, do the tests again and see if you get different results. If your problem was the sw, you will. If you get the same readings, I would bet on the wiring.l

Ed

 

[greaseyfingers]

I've already tried using a good working turn signal switch from my 89 Ranger and put in my 90 Ranger to see if that would correct the issue of both rear turn signals blinking in my 90 Ranger, but it didn't help..

I also tried removing the bulb on the Right front and Right rear turn signal socket and turned on the right turn signal switch, and the left rear turn signal bulb still flashes..

I even tried running a temporary ground wire from the negative battery post to the right rear turn signal light bulb socket when the bulb was installed, and both rear turn signal lights still flash..

I also cut off the right rear 3 wire turn signal socket and the left rear turn signal light still flashes..

When I put on the brakes, when the ignition switch is on, the rear turn signal lights will stop flashing and the right front turn signal light will stop flashing for as long as I'm depressing the brake pedal..

Even when the ignition switch is turned off, the passenger side front turn signal will light up, when the right turn signal switch is on, for as long as the brake pedal is being depressed..

I'm almost temped to cut off the passenger side front turn signal socket, (in case it's a bad socket), and see if that's the cause of my rear turn signals not working properly.

After doing some online searches for trying to find out the possible causes of both rear turn signals blinking on a vehicle..

I discovered that one possible cause for this happening, according to some peoples' experiences with this problem, is when a front turn signal bulb socket is shorting out, it can cause both rear turn signal lights to flash..

Does that sound possible?

 

[Mark_88]

Here is my 2¢ worth...if possible, why not look for a complete rear wire harness and swap it out?

Sounds like you have a grounding or contact issue...

I was having a ton of problems with my front wire harness and a generous member (Psycopete) on here shipped me one...I dragged my feet on installing it for about six months (mostly due to weather) but after I put it in finally all electrical problems vanished...

Just a thought...and that reminds me...have to get my battery and starter terminals cleaned up before the winter...