2005 Mustang Tail light Issue
Hi Guys-
The other day I got the fast ticking turn signal which tells me one of the turn signal bulbs is dead. I checked and sure enough
the left tail light has a bulb not flashing. I picked up some spares and replaced the bad bulb and the fast ticking has now
stopped, but the bulb still isn't working. I noticed that the same bulb on the right tail light is no longer working as well
now. The 2 bulbs that arent working are the inner most bulbs. I wasnt able to find a specific fuse that is tied to the
tail lights so I checked all the fuses under the hood and also on the SJB, they are all fine. I did read that it could be the
turn signal relay that is bad. I checked with Autozone and they dont sell that relay but was able to tell me the part number
for it (c1932a). I imagine I will need to go to Ford for that relay but was just wondering if anyone has had this problem before.
I have no idea where to find this turn signal relay on the car. I checked around the SJB and the fuses, nothing labeled close to the part
number I am looking for.
I tried the turn signal, brakes and hazards, the 2 bad bulbs never light up.
I have had the issue with the drain under the passenger side windshield wiper getting clogged and water has leaked over the SJB a few years ago.
The car has been running just fine since then. I am hoping that that isn't the cause because I am sure a replacement SJB is expensive lol
Looking at the tail lights from the rear, the X's are the bad bulbs
O O X X O O
Anyone have any ideas?
Thanks!
The other day I got the fast ticking turn signal which tells me one of the turn signal bulbs is dead. I checked and sure enough
the left tail light has a bulb not flashing. I picked up some spares and replaced the bad bulb and the fast ticking has now
stopped, but the bulb still isn't working. I noticed that the same bulb on the right tail light is no longer working as well
now. The 2 bulbs that arent working are the inner most bulbs. I wasnt able to find a specific fuse that is tied to the
tail lights so I checked all the fuses under the hood and also on the SJB, they are all fine. I did read that it could be the
turn signal relay that is bad. I checked with Autozone and they dont sell that relay but was able to tell me the part number
for it (c1932a). I imagine I will need to go to Ford for that relay but was just wondering if anyone has had this problem before.
I have no idea where to find this turn signal relay on the car. I checked around the SJB and the fuses, nothing labeled close to the part
number I am looking for.
I tried the turn signal, brakes and hazards, the 2 bad bulbs never light up.
I have had the issue with the drain under the passenger side windshield wiper getting clogged and water has leaked over the SJB a few years ago.
The car has been running just fine since then. I am hoping that that isn't the cause because I am sure a replacement SJB is expensive lol
Looking at the tail lights from the rear, the X's are the bad bulbs
O O X X O O
Anyone have any ideas?
Thanks!
SUPERCHARGED RED ROCKET ------------------Master-Moderator






Joined: May 11, 2006
Posts: 10,645
Likes: 2,511
From: Carnegie, PA
Hi Guys-
The other day I got the fast ticking turn signal which tells me one of the turn signal bulbs is dead. I checked and sure enough
the left tail light has a bulb not flashing. I picked up some spares and replaced the bad bulb and the fast ticking has now
stopped, but the bulb still isn't working. I noticed that the same bulb on the right tail light is no longer working as well
now. The 2 bulbs that arent working are the inner most bulbs. I wasnt able to find a specific fuse that is tied to the
tail lights so I checked all the fuses under the hood and also on the SJB, they are all fine. I did read that it could be the
turn signal relay that is bad. I checked with Autozone and they dont sell that relay but was able to tell me the part number
for it (c1932a). I imagine I will need to go to Ford for that relay but was just wondering if anyone has had this problem before.
I have no idea where to find this turn signal relay on the car. I checked around the SJB and the fuses, nothing labeled close to the part
number I am looking for.
I tried the turn signal, brakes and hazards, the 2 bad bulbs never light up.
I have had the issue with the drain under the passenger side windshield wiper getting clogged and water has leaked over the SJB a few years ago.
The car has been running just fine since then. I am hoping that that isn't the cause because I am sure a replacement SJB is expensive lol
Looking at the tail lights from the rear, the X's are the bad bulbs
O O X X O O
Anyone have any ideas?
Thanks!
The other day I got the fast ticking turn signal which tells me one of the turn signal bulbs is dead. I checked and sure enough
the left tail light has a bulb not flashing. I picked up some spares and replaced the bad bulb and the fast ticking has now
stopped, but the bulb still isn't working. I noticed that the same bulb on the right tail light is no longer working as well
now. The 2 bulbs that arent working are the inner most bulbs. I wasnt able to find a specific fuse that is tied to the
tail lights so I checked all the fuses under the hood and also on the SJB, they are all fine. I did read that it could be the
turn signal relay that is bad. I checked with Autozone and they dont sell that relay but was able to tell me the part number
for it (c1932a). I imagine I will need to go to Ford for that relay but was just wondering if anyone has had this problem before.
I have no idea where to find this turn signal relay on the car. I checked around the SJB and the fuses, nothing labeled close to the part
number I am looking for.
I tried the turn signal, brakes and hazards, the 2 bad bulbs never light up.
I have had the issue with the drain under the passenger side windshield wiper getting clogged and water has leaked over the SJB a few years ago.
The car has been running just fine since then. I am hoping that that isn't the cause because I am sure a replacement SJB is expensive lol
Looking at the tail lights from the rear, the X's are the bad bulbs
O O X X O O
Anyone have any ideas?
Thanks!
If you're certain it's the turn signal relay? you might want to consider www.tascaparts.com or www.rockauto.com as your best resources... Meanwhile, hope you're able to locate a replacement for the turn signal relay...
Administrator clevparts@aol.com





Joined: November 27, 2004
Posts: 12,556
Likes: 4,309
From: Visalia Ca.
@jetter
These Maybe Helpful.
{NOTE I REVISED THIS A FEW TIMES AS I CHASED THE DRAGON!}
Might Be able to Gleen a Few Idea's From This. I realize you Don't Have all the Diagnostic Gear!
The Relay the Partshouse listed Shows to Be a {Turn Signal Relay.}
Rock Auto Cataloging is Great Shows a Lot of Part Numbers Including Ford-Motorcraft!
https://www.rockauto.com/en/catalog/...,flasher,10139
I would Not Think the Flasher would Be the Issue But Unsure. {If Everything is Functioning Correctly Less the Two Bulbs Especially.}
If you have Any Aftermarket LED Bulbs in the System I would Replace with Oem Style to test!
I have Included Pdf's With Following Info.
Owners Manual, Exterior Lighting Shop Manual, Diagrams for Tail & Stop Lamps.
Added Flasher Pdf For Reference. It is Not From Ford it is ROCKAUTO Doc.
I FIND IT ODD THAT PARTS CATALOGS LIST A FLASHER YET THE SHOP MANUAL SAYS THIS! I SEEM TO REMEMBER THIS ISSUE FROM BACK IN THE DAY AS FAR AS LISTING A FLASHER YET NOT USING ONE. EVEN WHEN I WORKED IN FORD PARTS IN THE FACTORY CATALOGING! Sorry It's Been a Lot of Years!
SEE TURN SIGNAL & HAZARD LAMPS.
Stoplamps
The stoplamp outputs are controlled by the SJB. The stoplamp switch is monitored by the SJB. When the SJB detects the brake pedal is applied, the SJB processes this information and outputs voltage to the stoplamps.
Turn Signal and Hazard Lamps
All turn signal outputs are controlled by the SJB. The multifunction switch and the hazard switch are monitored by the SJB. When the multifunction switch is in the left or right turn position, or the hazard switch is engaged, the SJB processes this information and outputs voltage to the appropriate turn signal and hazard lamps. All turn signal lamps provide a lamp outage indication.
Parking, Rear or License Plate Lamps
The parking, rear, license plate and side marker lamps are controlled by the SJB. The headlamp switch is monitored by the SJB. When the headlamp switch is in the HEADLAMPS ON or PARKING LAMPS ON position, SJB processes this information and outputs voltage to the parking, rear, licence plate and side marker lamps.
Good Luck,
KC
These Maybe Helpful.
{NOTE I REVISED THIS A FEW TIMES AS I CHASED THE DRAGON!}
Might Be able to Gleen a Few Idea's From This. I realize you Don't Have all the Diagnostic Gear!
The Relay the Partshouse listed Shows to Be a {Turn Signal Relay.}
Rock Auto Cataloging is Great Shows a Lot of Part Numbers Including Ford-Motorcraft!
https://www.rockauto.com/en/catalog/...,flasher,10139
I would Not Think the Flasher would Be the Issue But Unsure. {If Everything is Functioning Correctly Less the Two Bulbs Especially.}
If you have Any Aftermarket LED Bulbs in the System I would Replace with Oem Style to test!
I have Included Pdf's With Following Info.
Owners Manual, Exterior Lighting Shop Manual, Diagrams for Tail & Stop Lamps.
Added Flasher Pdf For Reference. It is Not From Ford it is ROCKAUTO Doc.
I FIND IT ODD THAT PARTS CATALOGS LIST A FLASHER YET THE SHOP MANUAL SAYS THIS! I SEEM TO REMEMBER THIS ISSUE FROM BACK IN THE DAY AS FAR AS LISTING A FLASHER YET NOT USING ONE. EVEN WHEN I WORKED IN FORD PARTS IN THE FACTORY CATALOGING! Sorry It's Been a Lot of Years!
SEE TURN SIGNAL & HAZARD LAMPS.
Stoplamps
The stoplamp outputs are controlled by the SJB. The stoplamp switch is monitored by the SJB. When the SJB detects the brake pedal is applied, the SJB processes this information and outputs voltage to the stoplamps.
Turn Signal and Hazard Lamps
All turn signal outputs are controlled by the SJB. The multifunction switch and the hazard switch are monitored by the SJB. When the multifunction switch is in the left or right turn position, or the hazard switch is engaged, the SJB processes this information and outputs voltage to the appropriate turn signal and hazard lamps. All turn signal lamps provide a lamp outage indication.
Parking, Rear or License Plate Lamps
The parking, rear, license plate and side marker lamps are controlled by the SJB. The headlamp switch is monitored by the SJB. When the headlamp switch is in the HEADLAMPS ON or PARKING LAMPS ON position, SJB processes this information and outputs voltage to the parking, rear, licence plate and side marker lamps.
Good Luck,
KC
Last edited by 05stangkc; Jan 7, 2023 at 04:19 PM.
I been on a break for reasons. I do check in from time to time. But this time I checked in and saw this thread... I figured I might need to step in here. Guys, y'all overthought this just a tad in them replies, sorry.
OP, you state this:
This is the correct pattern for brake/turn signal lamps on the 2005-2009 stock setup. Only the outer two lamps will light up for brake/turn signals. The inner bulb only lights for running lights and nothing else. Your car is working correctly.
As to why Ford decided this to be the case, I do not know. It just is. I too find it strange and keep threatening to make a new harness to get that third bulb on brake/turn signal working. I have the spare harnesses and plugs and what not, but... I'm a stock guy on such things lest the car bite me for messin' with it, I guess.
As far as the SJB concern, yes, you might want to ensure the water's not getting in there anymore, but if this was your concern, the SJB is working correctly.
In case it matters, here is the wiring diagram for the turn signals/brake lamps for the 2005 Mustang, and it shows only the two bulbs per side, not three, and the Center High Mounted Stop Lamp (CHMSL).
https://iihs.net/fsm/?d=40&f=Turn%20...0Lamps.pdf&p=3
So there ya go. Hope that helps, good luck!
OP, you state this:
Looking at the tail lights from the rear, the X's are the bad bulbs
O O X X O O
O O X X O O
As to why Ford decided this to be the case, I do not know. It just is. I too find it strange and keep threatening to make a new harness to get that third bulb on brake/turn signal working. I have the spare harnesses and plugs and what not, but... I'm a stock guy on such things lest the car bite me for messin' with it, I guess.
As far as the SJB concern, yes, you might want to ensure the water's not getting in there anymore, but if this was your concern, the SJB is working correctly.
In case it matters, here is the wiring diagram for the turn signals/brake lamps for the 2005 Mustang, and it shows only the two bulbs per side, not three, and the Center High Mounted Stop Lamp (CHMSL).
https://iihs.net/fsm/?d=40&f=Turn%20...0Lamps.pdf&p=3
So there ya go. Hope that helps, good luck!
Administrator clevparts@aol.com





Joined: November 27, 2004
Posts: 12,556
Likes: 4,309
From: Visalia Ca.
@houtex
Thanks For the Bail Out! I have Had Sequential Lamps So Long My Memory was Fuzzy and Could Not See the Forest from the Tree's!
You are the Man!
I got to get My Tunnel Vision Checked! DOH!
KC
Thanks For the Bail Out! I have Had Sequential Lamps So Long My Memory was Fuzzy and Could Not See the Forest from the Tree's!
You are the Man!

I got to get My Tunnel Vision Checked! DOH!
KC
Last edited by 05stangkc; Jan 9, 2023 at 12:41 PM.
Lol I was just going to update this thread. I drove in too to work this morning in the dark so when I got there I went
to check to make sure they lights were still working and noticed that the 2 inner bulbs were now lit lol. If I turn off the headlights
those 2 bulbs go out. I guess I never noticed that those 2 bulbs were running lights in the 20 years I owned the car lol
Thanks a lot for all the help, I really appreciate it
to check to make sure they lights were still working and noticed that the 2 inner bulbs were now lit lol. If I turn off the headlights
those 2 bulbs go out. I guess I never noticed that those 2 bulbs were running lights in the 20 years I owned the car lol
Thanks a lot for all the help, I really appreciate it
Administrator clevparts@aol.com





Joined: November 27, 2004
Posts: 12,556
Likes: 4,309
From: Visalia Ca.
Thanks For Coming Back & Giving Closure! I know we Discussed the Odd Lamp Configuration back in the Day but That is a Gap that Keeps Getting Wider! All I Can Say about Myself is
.
Now get Some Sequential Lamps!
Enjoy that Car!
KC
. Now get Some Sequential Lamps!
Enjoy that Car!
KC
SUPERCHARGED RED ROCKET ------------------Master-Moderator






Joined: May 11, 2006
Posts: 10,645
Likes: 2,511
From: Carnegie, PA
Lol I was just going to update this thread. I drove in too to work this morning in the dark so when I got there I went
to check to make sure they lights were still working and noticed that the 2 inner bulbs were now lit lol. If I turn off the headlights
those 2 bulbs go out. I guess I never noticed that those 2 bulbs were running lights in the 20 years I owned the car lol
Thanks a lot for all the help, I really appreciate it
to check to make sure they lights were still working and noticed that the 2 inner bulbs were now lit lol. If I turn off the headlights
those 2 bulbs go out. I guess I never noticed that those 2 bulbs were running lights in the 20 years I owned the car lol
Thanks a lot for all the help, I really appreciate it
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