The Ford Barn

ross3655 · 04-10-2023, 12:01 PM

Was stopped by police for having a dim tail light on my 28 A. It only came with one running tail light. Police were right. You can hardly see it whether the car is running or not. Stop light works fine. Strangely the light goes on very brightly when I turn the switch from ON to BRIGHT. The head lights don’t work on bright, just the tail light brightly. I’ve juggled the tail light housing but still only dim results. WHAT CAN I DO? Larry

Brentwood Bob · 04-10-2023, 01:48 PM

Has wire harness been replaced?

Flathead Fever · 04-10-2023, 02:01 PM

A voltage drop from excessive resistance would cause as dim bulb. That's ff it's not the normal 6V dim lights. You need to look for the excessive resistance in the circuit using a voltmeter and a "voltage drop test". There are some good YouTube videos showing you how to perform the test. It's really easy and the only way to pinpoint where that resistance is in the circuit. You can pull the bulb and give it power and a ground directly from the battery to see how much brighter it is. That will tell you if it is excessive resistance in the circuit or just a dim bulb.

Tom Endy · 04-10-2023, 02:38 PM

Run a ground wire from the bulb socket to a solid ground on the frame. Years of rust and corrosion have probably built up at fender or body joints and you are not getting full battery voltage at the bulb. Also check the battery supply wire for good continuity.

Tom Endy

Y-Blockhead · 04-10-2023, 03:19 PM

Grounds, always check your grounds. Electrons do funny things when they can't make a complete circuit.

Richard Knight · 04-10-2023, 03:31 PM

Sponsored Links (Register now to hide all advertisements)

The running light is 3 candle power?, can be replaced by higher candle power bulb or switch to led lights as I did. Much safer. Possibly add brake lighter to rear window.

gdmn852 · 04-12-2023, 12:12 PM

Hello, as mentioned may have bad ground ,have seen that a lot, plus changing to higher candlepower bulb will help.

Gary WA · 04-12-2023, 01:20 PM

He just wanted to look at the car!!

Rob Doe · 04-13-2023, 05:11 AM

Les Andrews blue book, "diagnosis and troubleshooting", Chapter II, has excellent descriptions of voltage tests.

katy · 04-13-2023, 10:38 AM

Make sure the bulb is 6 volt, some PO may have put in a 12 volt bulb.
Also make sure the bulb is in the proper orientation, if it's in backwards that would explain why it goes BRIGHT when the headlights are turned on.

04-10-2023, 12:01 PM	#1
ross3655 Junior Member Join Date: Dec 2020 Location: Port Charlotte, FL Posts: 3	Dim tail light Was stopped by police for having a dim tail light on my 28 A. It only came with one running tail light. Police were right. You can hardly see it whether the car is running or not. Stop light works fine. Strangely the light goes on very brightly when I turn the switch from ON to BRIGHT. The head lights don’t work on bright, just the tail light brightly. I’ve juggled the tail light housing but still only dim results. WHAT CAN I DO? Larry

04-10-2023, 01:48 PM	#2
Brentwood Bob Senior Member Join Date: May 2010 Location: brentwood, ca Posts: 4,273	Re: Dim tail light Has wire harness been replaced?

04-10-2023, 02:01 PM	#3
Flathead Fever Senior Member Join Date: May 2010 Location: Yucaipa, CA Posts: 1,099	Re: Dim tail light A voltage drop from excessive resistance would cause as dim bulb. That's ff it's not the normal 6V dim lights. You need to look for the excessive resistance in the circuit using a voltmeter and a "voltage drop test". There are some good YouTube videos showing you how to perform the test. It's really easy and the only way to pinpoint where that resistance is in the circuit. You can pull the bulb and give it power and a ground directly from the battery to see how much brighter it is. That will tell you if it is excessive resistance in the circuit or just a dim bulb.

04-10-2023, 02:38 PM	#4
Tom Endy Senior Member Join Date: May 2010 Location: Southern California Posts: 3,134	Re: Dim tail light Run a ground wire from the bulb socket to a solid ground on the frame. Years of rust and corrosion have probably built up at fender or body joints and you are not getting full battery voltage at the bulb. Also check the battery supply wire for good continuity. Tom Endy

04-10-2023, 03:19 PM	#5
Y-Blockhead Senior Member Join Date: Jul 2011 Location: Redondo Beach, CA Posts: 5,855	Re: Dim tail light Grounds, always check your grounds. Electrons do funny things when they can't make a complete circuit.

04-10-2023, 03:31 PM	#6
Richard Knight Senior Member Join Date: Mar 2021 Posts: 130	Re: Dim tail light Sponsored Links (Register now to hide all advertisements) The running light is 3 candle power?, can be replaced by higher candle power bulb or switch to led lights as I did. Much safer. Possibly add brake lighter to rear window.

04-12-2023, 12:12 PM	#7
gdmn852 Senior Member Join Date: Feb 2019 Location: Erie Pa Posts: 689	Re: Dim tail light Hello, as mentioned may have bad ground ,have seen that a lot, plus changing to higher candlepower bulb will help.

04-12-2023, 01:20 PM	#8
Gary WA Senior Member Join Date: May 2010 Location: Clinton,WA/Whidbey Island Posts: 4,119	Re: Dim tail light He just wanted to look at the car!! __________________ www.whidbeymodelaclub.com Last edited by Gary WA; 12-30-2023 at 02:36 PM.

04-13-2023, 05:11 AM	#9
Rob Doe Senior Member Join Date: Apr 2021 Location: Central Illinois Posts: 499	Re: Dim tail light Les Andrews blue book, "diagnosis and troubleshooting", Chapter II, has excellent descriptions of voltage tests. __________________ "It ain't what you know for certain that gets ya in trouble. It's what ya know for certain that just ain't so!"

04-13-2023, 10:38 AM	#10
katy Senior Member Join Date: Jun 2015 Location: Red Deer, Alberta Posts: 5,057	Re: Dim tail light Make sure the bulb is 6 volt, some PO may have put in a 12 volt bulb. Also make sure the bulb is in the proper orientation, if it's in backwards that would explain why it goes BRIGHT when the headlights are turned on. __________________ If you don't hear a rumor by 10 AM, start one!. Got my education out behind the barn! Last edited by katy; 04-13-2023 at 10:40 AM. Reason: Addition