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


greaseyfingers

New member
Joined
Nov 4, 2007
Messages
339
Reaction score
0
Points
0
Age
47
Location
Crookston, Mn.
Vehicle Year
1987
Make / Model
Ford
Transmission
Manual
Even when I disconnect the rear brake/tail light wiriring harness on the driver's side fender well, when the ignition switch is turned off, the passenger side front turn signal/parking light will light up, (but doesn't flash), when the right turn signal switch is on, for as long as the brake pedal is being depressed..

That's why I'm wondering, if maybe the passenger side turn signal light is somehow shorting out inside the bulb socket and causing the problem..

Also, I'd like to find out how to correctly test the passenger side turn light socket with a OHM meter, or whatever is the best way to check it for shorting out, before deciding to cut it off, incase that isn't the problem, which would make more work in having to splice it back together, again..

You mentioned you were 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...

Do you recall if the electrical problems you were having, were similar the electrical problems I'm having..

When you replaced the wiring harness, the under dash fuse block looks like it's attached to the wiring harness, too, isn't it..

How long did it take to replace the wiring harness, you mentioned doing, as it looks like it would be a big job..
 
Last edited:


Rock Auto 5% Discount Code: 57CD9601BD5AB4 Expires: July 1, 2019

enjr44

Active member
U.S. Military - Veteran
Joined
Mar 24, 2013
Messages
1,138
Reaction score
6
Points
38
Age
75
Location
Renton, WA
Vehicle Year
02 2X4; 08 FX4
Make / Model
Ford
Engine Size
4.0 SOHC
Transmission
Automatic
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
Did you do the tests I described???? If not why not???
 

greaseyfingers

New member
Joined
Nov 4, 2007
Messages
339
Reaction score
0
Points
0
Age
47
Location
Crookston, Mn.
Vehicle Year
1987
Make / Model
Ford
Transmission
Manual
I haven't had a chance to, yet, due to all of the rainy weather we've been having..

Today is the first day it hasn't been raining for some time..

I don't know if I'll have time to do it today, as I have some other things that need getting done..

I'll test these wires, as you mentioned doing, when I get a chance to and let you know the results..
 

Mark_88

New member
Joined
Aug 11, 2007
Messages
18,550
Reaction score
221
Points
0
Age
63
Location
Ontario, Canada
Vehicle Year
2007
Make / Model
Dordge
Engine Size
3.3 Fuel Injected
Transmission
Automatic
My credo
Love Thy Neighbor
You mentioned you were 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...

Do you recall if the electrical problems you were having, were similar the electrical problems I'm having..

When you replaced the wiring harness, the under dash fuse block looks like it's attached to the wiring harness, too, isn't it..

How long did it take to replace the wiring harness, you mentioned doing, as it looks like it would be a big job..
The front light/battery/horn/ignition harness took all of 60 minutes, and that was only because I had to splice the ten wires in the harness to the old harness just before the connector.

If your truck is the 87 in your details then the rear harness connects just inside engine bay near the firewall...probably take you all of an hour to remove the old harness and install a replacement...but you may have to actually lift the box to get at the fuel tank connector...unless yours is on a different harness...I keep forgetting that mine is only the fuel gauge because I don't have a pump in the tank.

But you've got some good test procedures to follow so you might try that first...only say that because if the problem is before the connector to the rear then the only thing you will accomplish is to know you've done that part...

Does your fuel gauge work? Reverse lights? They are on the same harness...
 

greaseyfingers

New member
Joined
Nov 4, 2007
Messages
339
Reaction score
0
Points
0
Age
47
Location
Crookston, Mn.
Vehicle Year
1987
Make / Model
Ford
Transmission
Manual
The front light/battery/horn/ignition harness took all of 60 minutes, and that was only because I had to splice the ten wires in the harness to the old harness just before the connector.

If your truck is the 87 in your details then the rear harness connects just inside engine bay near the firewall...probably take you all of an hour to remove the old harness and install a replacement...but you may have to actually lift the box to get at the fuel tank connector...unless yours is on a different harness...I keep forgetting that mine is only the fuel gauge because I don't have a pump in the tank.

But you've got some good test procedures to follow so you might try that first...only say that because if the problem is before the connector to the rear then the only thing you will accomplish is to know you've done that part...

Does your fuel gauge work? Reverse lights? They are on the same harness...
To put a replacement harness in 60 minutes, sounds like getting the job done in record time, considering you mentioned having to splice the ten wires in the harness to the old harness just before the connector.

Where did you have to spice these 10 wires in at, under the dash, or along the fire wall, somewhere.

Had the connectors already been cut off the harness you installed, so you had to spice your old ones to the replacement harness

I have a 87 Ranger, and a 89 Ranger, but the electrical problems are on my 90 Ranger.

The reverse lights work on the 90 Ranger, but the fuel gauge doesn't since I've owned it, thinking maybe the float on the sending unit isn't floating, as it registers empty all the time.

I still haven't a chance to do the test procedures, on the rear brake light wiring, as I was informed how to do, by another TRS member.
 
Last edited:

greaseyfingers

New member
Joined
Nov 4, 2007
Messages
339
Reaction score
0
Points
0
Age
47
Location
Crookston, Mn.
Vehicle Year
1987
Make / Model
Ford
Transmission
Manual
if both lights blink in unison and are both bright, i would suspect the turn signal switch. it may be shorting in the brake light circuit, as it runs through the turn signal switch, but only for the rear. i have had the same problem before, turned out to be metal shavings from the horn contact stuck in the grease in the turn signal switch! that was from a car built in the late 60's, not sure if there is dielectric grease in the newer switches. hope this helps
After installing a new turn signal switch that I bought on ebay..

Both rear turn signals are still flashing, when ever the the right turn signal is used..

When I disconnected the wire connection plug to the turn signal switch, and used a jumper wire to the turn signal switch's connection plug's wire terminal for the right front turn signal light and to the right rear turn signal light's terminal, and connected it to the power wire's terminal on the connection plug for the turn signal switch..

Both the right front and back turn signals would worked fine, without causing the left rear turn signal light to flash, too..

So, why do both rear turn signals still flash, as before, when the turn signal's connection wire plug connector is connected to a brand new turn signal switch that I purchased on ebay..

What would be causing both rear turn signals to flash, when using the right turn signal..

When I disconnected the wire connection plug to the turn signal switch, and used a jumper wire to the turn signal switch's connection plug's wire terminal for the right front turn signal light and to the right rear turn signal light's terminal, and connected it to the power wire's terminal on the connection plug for the turn signal switch, the right side turn signal's front and rear lights will work fine, without the left rear turn signal light flashing too..

Would this seem to indicate that the problem is in the wire connection plug to the turn signal switch..

Does anyone have a spare one, if you think that's what's causing the problem..
 
Last edited:

Techkraut

New member
Joined
Nov 11, 2018
Messages
1
Reaction score
0
Points
0
Location
Fallbrook, CA
Vehicle Year
1999
Make / Model
Ford
Transmission
Automatic
Were you ever able to solve this problem? If so, what was the cause? I have a very similar problem.
 


Top