88 Lx Turn Signals Don't Work

Chuckleb0ne · Jun 19, 2016

Hey guys, new here to stangnet. I had recently picked up a 1988 Mustang LX that had a 5.0 HO conversion done to it. Everything was working fine except for the messy wiring. I found out a couple days back that my instrument cluster lights were not working. The most common cause to this problem is usually the dimmer switch, so I replaced that and some lights came back on, others still left in the dark. So I took out the whole instrument cluster and found out the the plastic/copper seal was broken in one place, so not wanting to buy a new instrument cluster I decided to modify the lights and wire them to a fuse to turn on when the Ignition is on.

It was sketchy, but it definitely worked. Now, when I put everything back together behind the instrument cluster (2 wiring harnesses & speedo cable) and then bolted everything back up, I took it for a test run and everything was great. Except that my turn signals did not work. No flashing light on the dash, no clicking, no lights in the rear taillamps. I proceeded to check the hazard flasher fuse (cylinder looking fuse) and replaced that. Then I replaced the turn signal flasher fuse (another cylinder), and still no turn signals.

The only thing that I can go off of is that there is this harness with the same flasher wires that was poking out of the bottom of the dash. I had not noticed this before taking apart the instrument cluster. I will include a picture below.

My question is, does this connector have anything to do with the turn signals? And where should I begin trying to troubleshoot this damn problem?

Any help will be appreciated!

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JD1964 · Jun 19, 2016

The turn signals also have a regular type fuse too. (not cylindrical) The cylinder pieces you say you changed are flashers, not fuses. Check a fuse box diagram for the location of the turn signal fuse and check/replace it. It's common to blow fuses when messing around under the dash.

I cant identify the harness you show in the pic. Sorry bout that

Chuckleb0ne · Jun 19, 2016

John Dirks Jr said:
The turn signals also have a regular type fuse too. (not cylindrical) The cylinder pieces you say you changed are flashers, not fuses. Check a fuse box diagram for the location of the turn signal fuse and check/replace it. It's common to blow fuses when messing around under the dash.

I cant identify the harness you show in the pic. Sorry bout that

I checked the actual turn signal fuse as well. It looks OK not broken. I went ahead and tested the fuse and it was still operational. So now I am stumped. I am gonna open up the instrument cluster again and check it over. I am not expecting anything wrong though as everything else works.

Are there any harnesses that work with the turn signal? Is it just on the steering column?

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Chuckleb0ne · Jun 19, 2016

I had a 30 fuse blown, but I replaced that and still nothing.

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JD1964 · Jun 19, 2016

Try the 4 way emergency flashers. Do they work?

Chuckleb0ne · Jun 20, 2016

John Dirks Jr said:
Try the 4 way emergency flashers. Do they work?

Nope. I checked behind the hazard switch and connection is good and wires are solid. The hazard flasher was good, but I don't think those would effect the turn signals.

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JD1964 · Jun 20, 2016

Hazards and turn signals are all in the same wiring and circuit, so problems can be related.

Sounds like you got a power or ground fault

Chuckleb0ne · Jun 20, 2016

John Dirks Jr said:
Hazards and turn signals are all in the same wiring and circuit, so problems can be related.

Sounds like you got a power or ground fault

Hmmm.... I'll go ahead and remove the instrument cluster again and see if missed anything. I am an amateur at wiring for cars, it is gonna be a pain in the ass to figure this out lol.

Appreciate the help. [emoji106]

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jrichker · Jun 20, 2016

87-90 Mustang Turn signal troubleshooting

The ignition switch is also known for creating turn signal problems. Make sure the ignition switch and wiring are in good shape as a first item to check. This is especially true if you are having problems with things like the radio and heater/AC blower.

Ignition switch wiring

Some of the symptoms of ignition switch problems are things that don’t work or are intermittent like radio, turn signals, wipers or heater. The auto parts stores sell the switches for $13-$15.

While you are working on the switch, check the wiring and connector closely. A replacement connector with new wiring pigtails is available from most auto parts stores

AutoZone and Advanced Auto Parts have the same Part Number: 434 - may have to order, not always in stock

Advanced Auto Parts alternate part number: PT5534

If just the plastic shell is broken, a small jewelers screwdriver inserted from the front will release the contacts from the connector shell. Do this one wire at time and insert the wire and connector you removed into the same position on the replacement connector shell.

Saleen0679 was nice enough to dig this up for us awhile back: Replace a 1979-1993 Ignition Switch Assembly

Torx bit set from Advance Auto Parts

Autocraft torx bit set – have small hole in tip for tamper proof screws.
Part No. AC571/W1386 Cost approx. $12 +tax

87-90 Mustang Turn signal troubleshooting

turn-signal-wiring-87-90-mustang-jpg.545554

Keep in mind that the flasher on the front of the fuse panel is for the hazard flasher. Locate the turn signal flasher, depending on the model year it may be behind the radio or on the backside of the fuse panel or behind the glove compartment.

Turn the ignition switch to Run; the engine does not need to be running for these tests. With the turn signal flasher removed, test the pink/orange wire for 12 volts.

Set the voltmeter to DC volts and select the scale that is closest to 12 volts. Clip one voltmeter probe on the bare metal part of the car body for a ground and put the other probe in the turn signal flasher socket contact that has the pink/orange wire. You should see about 12 volts.

No 12 volts present: replace the fuse and check for 12 volts again as described above. Do not turn the ignition switch off if you are testing for voltage.

Still no 12 volts, pull the fuse and test the #5 fuse socket contacts for 12 volts. One contact will have 12 volts. One probe is grounded, the other probe gets stuck in the fuse contacts. Test both contacts for 12 volts.

No 12 volts on either fuse contact, the ignition switch or ignition switch wiring is suspect. Move things around so that you can get to the backside of the ignition switch wiring connector with the ignition switch still connected to it. Make sure that you don't turn the ignition switch OFF while you are testing it. It still needs to be in the Run position. Look for 12 volts on the large gray/yellow wire. No 12 volts and you have a bad ignition switch or some bad wiring. Wiggle the large gray/yellow wire to see if it gets or loses voltage while you are checking it.

Diagrams courtesy of Tmoss & Stang&2birds

Fuse box layout

Ignition switch wiring

Once you have located the turn signal flasher, remove it from its socket and jumper the socket contacts together. Turn the ignition switch to Run and try both left and right turn signals. They should come on steady if you have good 12 volts to the pink/orange wire. If the lights turn on steady and bright, that means the flasher is suspect. If you find one more bulbs do not come on steady and bright, then you have either a bad bulb, bad ground at the bulb socket or a corroded or bad socket.

If you still have problems, then it is the multifunction switch, or its wiring; that is a case of last resort.

Multifunction turn signal switch:
Before you think about replacing the multifunction switch with one from the junkyard, here are some things to be aware of...

The problem is more common in GT models because they had fog lights on the same power wiring as the headlights. Ford undersized the wire and that caused problems.

A word of caution about multifunction switches is in order here. The multifunction switch (high/low beam, wiper, turn signals) are different for different years. 87-98 will work in any 87-89 car. The 90-93 switches only work in 90-93 cars. You can't put an early model switch in a late model car, nor can you put a late model switch in an early car.

Supposedly you can move the pins around to make the switches work in model years that are different from the car the switch came out of. I cannot verify that and haven’t tried it.

Other possible problem sources for the turn signal & headlight malfunction are the ignition switch, multifunction switch and the plastic shell that holds the turn signal wiring connector pins.

The following diagram is for 87-89 model cars.

Turn signal switch wiring:

The following diagram is for 90-93model cars.

Turn signal switch wiring:

92-93-mustang-turn-signal-circuit-jpg.537013

Chuckleb0ne · Jun 20, 2016

Thanks for the information. I will go ahead and follow the instructions and see if I can find anything wrong. Will report back if successful.

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Chuckleb0ne · Jun 25, 2016

jrichker said:
87-90 Mustang Turn signal troubleshooting

The ignition switch is also known for creating turn signal problems. Make sure the ignition switch and wiring are in good shape as a first item to check. This is especially true if you are having problems with things like the radio and heater/AC blower.

Ignition switch wiring

Some of the symptoms of ignition switch problems are things that don’t work or are intermittent like radio, turn signals, wipers or heater. The auto parts stores sell the switches for $13-$15.

While you are working on the switch, check the wiring and connector closely. A replacement connector with new wiring pigtails is available from most auto parts stores

AutoZone and Advanced Auto Parts have the same Part Number: 434 - may have to order, not always in stock

Advanced Auto Parts alternate part number: PT5534

If just the plastic shell is broken, a small jewelers screwdriver inserted from the front will release the contacts from the connector shell. Do this one wire at time and insert the wire and connector you removed into the same position on the replacement connector shell.

Saleen0679 was nice enough to dig this up for us awhile back: Replace a 1979-1993 Ignition Switch Assembly

Torx bit set from Advance Auto Parts

Autocraft torx bit set – have small hole in tip for tamper proof screws.
Part No. AC571/W1386 Cost approx. $12 +tax

87-90 Mustang Turn signal troubleshooting

Keep in mind that the flasher on the front of the fuse panel is for the hazard flasher. Locate the turn signal flasher, depending on the model year it may be behind the radio or on the backside of the fuse panel or behind the glove compartment.

Turn the ignition switch to Run; the engine does not need to be running for these tests. With the turn signal flasher removed, test the pink/orange wire for 12 volts.

Set the voltmeter to DC volts and select the scale that is closest to 12 volts. Clip one voltmeter probe on the bare metal part of the car body for a ground and put the other probe in the turn signal flasher socket contact that has the pink/orange wire. You should see about 12 volts.

No 12 volts present: replace the fuse and check for 12 volts again as described above. Do not turn the ignition switch off if you are testing for voltage.

Still no 12 volts, pull the fuse and test the #5 fuse socket contacts for 12 volts. One contact will have 12 volts. One probe is grounded, the other probe gets stuck in the fuse contacts. Test both contacts for 12 volts.

No 12 volts on either fuse contact, the ignition switch or ignition switch wiring is suspect. Move things around so that you can get to the backside of the ignition switch wiring connector with the ignition switch still connected to it. Make sure that you don't turn the ignition switch OFF while you are testing it. It still needs to be in the Run position. Look for 12 volts on the large gray/yellow wire. No 12 volts and you have a bad ignition switch or some bad wiring. Wiggle the large gray/yellow wire to see if it gets or loses voltage while you are checking it.

Diagrams courtesy of Tmoss & Stang&2birds

Fuse box layout

Ignition switch wiring

Once you have located the turn signal flasher, remove it from its socket and jumper the socket contacts together. Turn the ignition switch to Run and try both left and right turn signals. They should come on steady if you have good 12 volts to the pink/orange wire. If the lights turn on steady and bright, that means the flasher is suspect. If you find one more bulbs do not come on steady and bright, then you have either a bad bulb, bad ground at the bulb socket or a corroded or bad socket.

If you still have problems, then it is the multifunction switch, or its wiring; that is a case of last resort.

Multifunction turn signal switch:
Before you think about replacing the multifunction switch with one from the junkyard, here are some things to be aware of...

The problem is more common in GT models because they had fog lights on the same power wiring as the headlights. Ford undersized the wire and that caused problems.

A word of caution about multifunction switches is in order here. The multifunction switch (high/low beam, wiper, turn signals) are different for different years. 87-98 will work in any 87-89 car. The 90-93 switches only work in 90-93 cars. You can't put an early model switch in a late model car, nor can you put a late model switch in an early car.

Supposedly you can move the pins around to make the switches work in model years that are different from the car the switch came out of. I cannot verify that and haven’t tried it.

Other possible problem sources for the turn signal & headlight malfunction are the ignition switch, multifunction switch and the plastic shell that holds the turn signal wiring connector pins.

The following diagram is for 87-89 model cars.

Turn signal switch wiring:

The following diagram is for 90-93model cars.

Turn signal switch wiring:

Okay. So I spent about 3 hours trying to troubleshoot all the turn signal wiring, and I may have figured out that both the hazard flasher and the turn signal flasher are not getting any power. It should read 12V but it is nothing, not even a test light can turn on. It could be that I was checking the wrong ports, but this would explain turn signals not working.

I can't seem to figure this out. When removing the instrument cluster I didn't touch any of the harnesses or fuse box wires, so I don't get how my turn signals would just all of a sudden stop working.

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Chuckleb0ne · Jun 25, 2016

And another note, the hazard switch in my car does not work. Even when I purchased the vehicle it didn't have the hazards working. I looked on the back of the switch and there were a couple of wires that came out, and they won't stay inside the connector housing. I tried looking online to see if anyone was selling the ponytail connector for the hazard switch and I couldn't find anything.

Regardless of he hazard switch not working, the turn signals operated perfectly fine without it working. Was just wondering if it had a role to play in the problem I am having.

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jrichker · Jun 26, 2016

Chuckleb0ne said:
And another note, the hazard switch in my car does not work. Even when I purchased the vehicle it didn't have the hazards working. I looked on the back of the switch and there were a couple of wires that came out, and they won't stay inside the connector housing. I tried looking online to see if anyone was selling the ponytail connector for the hazard switch and I couldn't find anything.

Regardless of he hazard switch not working, the turn signals operated perfectly fine without it working. Was just wondering if it had a role to play in the problem I am having.

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Compare the colors on the loose wires on the diagrams I posted.
Then double check the ignition switch & fuse...

Diagrams courtesy of Tmoss & Stang&2birds

Ignition switch wiring

Fuse box layout

Chuckleb0ne · Jun 26, 2016

@jrichker

I just found a loose hot wire hanging near the back of the fuse box. Looks orange and green. Is this the red/Lt green wire?

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jrichker · Jun 26, 2016

Chuckleb0ne said:
@jrichker

I just found a loose hot wire hanging near the back of the fuse box. Looks orange and green. Is this the red/Lt green wire?

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Compare it to the other wires with either a red primary color or stripe.

That may be the missing hazard flasher power wire...

Let's start at the beginning; with any electrical circuit, you start troubleshooting at the point where it gets its power. In this case that would be the Ignition switch.
Turn the ignition switch to Run and remove the #5 & #8 wires. No good 12 volts and you have an ignition switch problem.

Chuckleb0ne · Jun 30, 2016

@jrichker

When you say take the #5 & #8 wires out, do you mean on the back of the fuse box? And both wires should be getting full 12v?

Thanks!

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jrichker · Jun 30, 2016

Chuckleb0ne said:
@jrichker

When you say take the #5 & #8 wires out, do you mean on the back of the fuse box? And both wires should be getting full 12v?

Thanks!

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No.

Check the fuses and put the fuses back in if they are good. Then turn the ignition switch to Run. Make sure you have good 12 volts on both sides of the #5 & #8 fuses. Do not remove any wires, use a safety pin to probe the backside of the fuse panel if you can't get to the metal contacts for the fuses.

Chuckleb0ne · Jul 2, 2016

jrichker said:
No.

Check the fuses and put the fuses back in if they are good. Then turn the ignition switch to Run. Make sure you have good 12 volts on both sides of the #5 & #8 fuses. Do not remove any wires, use a safety pin to probe the backside of the fuse panel if you can't get to the metal contacts for the fuses.

I don't have 12v on those two fuses. I found out that the #8 fuse wasn't even in. I replaced that and now the key chime is back, but still no turn signals. Pics of multimeter on #5-#8 fuses respectively.

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Chuckleb0ne · Jul 2, 2016

On another note, key chime noise won't stop even when car is started and door is closed.

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jrichker · Jul 3, 2016

If you were to re-read my previous posts, you would find out that no 12 volts at fuse positions #5 & #8 with the ignition switch in the Run position meant a bad ignition switch...

Fix that first and maybe the chime problem will get fixed in the process.

Recall on Ford Ignition switches:

Revised 7-June-2014 to add Torx bit picture and source. Also added replacement ignition switch wiring pigtail picture, part numbers and sources.

Some of the symptoms of ignition switch problems are things that don’t work or are intermittent like radio, turn signals, wipers or heater.

There was a FREE recall on Ford ignition switches. They overheat and sometimes catch fire. That burns up the steering column and sometimes the car interior. Since this is very old information, you may not be able to get the switch replaced for free anymore. The auto parts stores sell the switches for $13-$15.

While you are working on the switch, check the wiring and connector closely. A replacement connector with new wiring pigtails is available from most auto parts stores

AutoZone and Advanced Auto Parts have the same Part Number: 434 - may have to order, not always in stock

Advanced Auto Parts alternate part number: PT5534

Saleen0679 was nice enough to dig this up for us awhile back: Replace a 1979-1993 Ignition Switch Assembly

Torx bit set from Advance Auto Parts

Autocraft torx bit set – have small hole in tip for tamper proof screws.
Part No. AC571/W1386 Cost approx. $12 +tax

Diagrams courtesy of Tmoss & Stang&2birds

Ignition switch wiring

Fuel, alternator, A/C and ignition wiring

88 Lx Turn Signals Don't Work

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