Go Back   The Ford Barn > General Discussion > Model A (1928-31)

Sponsored Links (Register now to hide all advertisements)

Reply
 
Thread Tools Display Modes
Old 05-29-2019, 07:59 AM   #1
hangarb7
Senior Member
 
Join Date: May 2014
Location: North Versailles, PA
Posts: 133
Talking Lighting dims question

Here is the deal. I have had this car, which was rebuilt in the early '90's ('30 Tudor) for 11 years

Same problem since day one, so I will tell what I have done and tell me if it is normal.

I have added ground wires to every light, including tailights. I have run a seperate ground to the generator and the starter ( a heavy braid on that). I have turned up the 6V generator so that it is now putting out 8-10amps at cruise, and -2 to -4 with headlights on. All lights at idle and cruise are fairly bright (I mean, you know what I mean). Output of gen is 6.8V. I have replaced the light switch with a new Snyders (excellent quality) unit. I have also completely gone over the wiring of the car and the joints are soldered and the wiring is according to the diagram.

I have not changed the original cutout since the battery is always up. Battery is the second one and is about six years old, however I have had this problem since the beginning.

Turn on the lights, but as soon as I hit the brakes, lights dim considerably. Also, with lights on (no brake lights yet), horn just says 'eeeeer', although I have a great horn without the lights on.

So, question.... any suggestions? Or is this normal ops?

Thanks for any reply
hangarb7 is offline   Reply With Quote
Old 05-29-2019, 08:48 AM   #2
Jacksonlll
Senior Member
 
Jacksonlll's Avatar
 
Join Date: Jul 2012
Location: Michigan-- Member of Oakleaf of MARC
Posts: 1,262
Send a message via ICQ to Jacksonlll
Default Re: Lighting dims question

Take a hard look at your brake light circuit. Surprised your fuse has not blown.
Jacksonlll is offline   Reply With Quote
Sponsored Links (Register now to hide all advertisements)
Old 05-29-2019, 09:18 AM   #3
ryanheacox
Senior Member
 
ryanheacox's Avatar
 
Join Date: Apr 2013
Location: Northwest CT
Posts: 623
Default Re: Lighting dims question

What type of bulbs are you using?
ryanheacox is offline   Reply With Quote
Old 05-29-2019, 09:40 AM   #4
Dick Steinkamp
Senior Member
 
Dick Steinkamp's Avatar
 
Join Date: Apr 2016
Location: Bellingham, WA
Posts: 1,158
Default Re: Lighting dims question

It's not normal. You may have two issues. One being resistance in the brake light circuit. The other being a horn that needs to be lubed and adjusted.
__________________
All steel from pedal to wheel
Dick Steinkamp is offline   Reply With Quote
Old 05-29-2019, 09:53 AM   #5
Badpuppy
Senior Member
 
Join Date: Dec 2017
Location: Guthrie, OK
Posts: 509
Default Re: Lighting dims question

Check voltage across the cutout at fast idle and lights on. If it's much more than 1/2 volt or so the contacts are pitted; repair or replace.

Generator may need overhaul.
Badpuppy is offline   Reply With Quote
Old 05-29-2019, 10:13 AM   #6
alexiskai
Senior Member
 
alexiskai's Avatar
 
Join Date: Apr 2018
Location: Mebane NC
Posts: 321
Default Re: Lighting dims question

It's implied in earlier comments, but I would look specifically at the stop light switch, which is the device under the driver's floorboard that closes the circuit to the brake light when the brake pedal is pushed. There may be some kind of high-resistance grounding occurring when the switch is actuated that would cause a current drop in the other lamps. You can buy a new stop light switch for under $10 (the nice ones are $50, but for troubleshooting purposes the cheap one would suffice).
alexiskai is offline   Reply With Quote
Old 05-29-2019, 10:14 AM   #7
Bob C
Senior Member
 
Join Date: May 2010
Location: So Cal
Posts: 6,463
Default Re: Lighting dims question

I agree with Dick. Since you know the problem with the lights are in the brake light
circuit I would start with the brake light switch as that is a know problem area.


Bob
Bob C is offline   Reply With Quote
Old 05-29-2019, 10:21 AM   #8
alexiskai
Senior Member
 
alexiskai's Avatar
 
Join Date: Apr 2018
Location: Mebane NC
Posts: 321
Default Re: Lighting dims question

You can also try to isolate the problem by disconnecting the wire at the stop light switch that goes back to the brake light. If the wire is detached and the headlamps still dim when the brake pedal is pushed, that's gotta be an issue with the switch itself.
alexiskai is offline   Reply With Quote
Old 05-29-2019, 10:38 AM   #9
Patrick L.
Senior Member
 
Patrick L.'s Avatar
 
Join Date: May 2010
Location: Upstate NY and western Florida
Posts: 5,188
Default Re: Lighting dims question

I too think there are 2 issues. One with the brake light switch or switch to light circuit. The switch is simple and problem shouldn't be too hard to find.


The second with the horn.


Does the dim issue stop when the brake light switch is released ? [ foot taken off pedal]
Patrick L. is offline   Reply With Quote
Old 05-29-2019, 10:39 AM   #10
Kurt in NJ
Senior Member
 
Kurt in NJ's Avatar
 
Join Date: May 2010
Location: on the Littlefield
Posts: 4,831
Default Re: Lighting dims question

A grind had a similar problem with a packard, the previous owner must have had the problem also, the car came with every type of brake bulb-- regular, halogen, led, different designs of each, none were bright, it even got a new wiring harness , I traced the power loss to rusty nuts in the ammeter---- there were no problems with driving or battery charging
The back of the ammeter was getting hot---- hold the brakes for a while , run the lights, feel around or take voltmeter and look for losses
Kurt in NJ is offline   Reply With Quote
Old 05-29-2019, 11:48 AM   #11
Tom Endy
Senior Member
 
Tom Endy's Avatar
 
Join Date: May 2010
Location: Southern California
Posts: 2,473
Default Re: Lighting dims question

It is probable that the ground cable connection where it attaches to the frame is corroded and not making a good electrical connection. It is out of sight and may have been years since it was cleaned. You will have to remove the battery to get to it. Remove the bolt, nut and the cable and clean them thoroughly. Take an abrasive of some sort and clean all the corrosion and paint off the mounting boss on the frame.

Tom Endy
Tom Endy is offline   Reply With Quote
Old 05-29-2019, 12:09 PM   #12
100IH
Senior Member
 
Join Date: Dec 2011
Location: SW Idaho
Posts: 906
Default Re: Lighting dims question

Tail lamp ground is possible ground issue. Do as you have done already, add a temporary ground to the lamp,bypassing the fender and body. Battery may be hurting due to high charging rate - 2- 4 amps setting, don't worry about the momentary negative readings. if amp readings are read from the dash, invest in a meter to go inline and don't rely on the dash meter . Check inside the junction box for loose nuts & solder joints.
100IH is offline   Reply With Quote
Old 05-29-2019, 03:49 PM   #13
Patrick L.
Senior Member
 
Patrick L.'s Avatar
 
Join Date: May 2010
Location: Upstate NY and western Florida
Posts: 5,188
Default Re: Lighting dims question

I thought you had looked at every possibility of a poor ground, then I re-read the post. I guess I mis-read it. I agree your issue could also be a poor ground anywhere including the battery and/or tail lamp. So there a couple more things to look at. Let us know what it is.
Patrick L. is offline   Reply With Quote
Old 05-29-2019, 07:46 PM   #14
jax55
Senior Member
 
jax55's Avatar
 
Join Date: May 2014
Location: Santa Barbara, Ca
Posts: 329
Default Re: Lighting dims question

I am adding this only because it was not mentioned above, I know you have replaced the battery once..but did you clean the posts and inside of the cables that contact the posts?
I have seen this happen, things seem OK but there is poor contact at those points.
jax55 is offline   Reply With Quote
Old 05-29-2019, 08:16 PM   #15
Penthode
Member
 
Penthode's Avatar
 
Join Date: Oct 2016
Posts: 47
Default Re: Lighting dims question

There is only one of two reasons for the lights dimming. But first, what is the ammeter reading?

1. If the ammeter indicates a heavy discharge (needle pegged negative), then there is a short circuit in the brake light circuit is providing an extra heavy load. CAUTION: DISCONNECT THE BATTERY AND LOOK AT THE BRAKE SWITCH AND WIRING TO THE TAIL LIGHT.

2. If the a meter does not show a heavy discharge, then there is a poor connection (high resistance) between battery terminal and the common distribution point shared between the headlamps and the brake circuit. The common point is generally at the head lamp switch at the base of the steering column which means the high resistance will be before this point.

If following number 2, to determine where the high resistance point is, you need a digital voltmeter to measure the voltage drop at various points.

With someone stamping on the brakes, use the voltmeter starting at the battery. Take note of the voltage to ground and then move progressively along the circuit taking measurements until you find a higher than expected voltage drop. (You will find a normal drop of 0.2 to about 0.4 volts between battery and lamp connection. If it is more than 0.5 volts, the is a bad wire or connection in the circuit). This way you can isolate the high resistance section causing the drop responsible for the dimmed lights.

Last edited by Penthode; 05-29-2019 at 09:09 PM.
Penthode is offline   Reply With Quote
Old 05-29-2019, 08:49 PM   #16
Penthode
Member
 
Penthode's Avatar
 
Join Date: Oct 2016
Posts: 47
Default Re: Lighting dims question

I just reread your original post. You indicate that even with no brakes applied, the horn diminishes with just the lights on.

This points to a bad (high resistance) common connection. If the battery ground was bad the generator alone would make the lights too bright.

Is the engine properly grounded? Are the connections to the terminal box good? The highest probability is the ammeter is partially open or the connections to it are bad. (You can check a bad ammeter by shorting together the two terminals on the junction box).

You need the digital meter as it will precisely show where the voltage drop loss occurs. The meter is cheap and will prove very useful.

Last edited by Penthode; 05-29-2019 at 09:11 PM.
Penthode is offline   Reply With Quote
Old 05-30-2019, 10:04 AM   #17
Badpuppy
Senior Member
 
Join Date: Dec 2017
Location: Guthrie, OK
Posts: 509
Default Re: Lighting dims question

I'm sure it's the cutout. If not, I would eat my hat, except my hat was consumed long ago.
Badpuppy is offline   Reply With Quote
Old 05-30-2019, 10:49 AM   #18
Penthode
Member
 
Penthode's Avatar
 
Join Date: Oct 2016
Posts: 47
Default Re: Lighting dims question

Quote:
Originally Posted by Badpuppy View Post
I'm sure it's the cutout. If not, I would eat my hat, except my hat was consumed long ago.
There is a logical way of looking at this. If you read a constant nominal 6 volts at the battery and it does not change when the brakes are applied, it is not the cut-out.

A methodical measurement process with a digital multimeter will quickly reveal the problem. My guess is the wiring to and through the ammeter.
Penthode is offline   Reply With Quote
Old 05-30-2019, 09:15 PM   #19
Tom Wesenberg
Senior Member
 
Tom Wesenberg's Avatar
 
Join Date: May 2010
Location: Mpls, MN
Posts: 27,442
Default Re: Lighting dims question

Do you use a fuse, and does it blow when you step on the brake pedal?
I'd remove the power wire on the brake switch and see if the problem goes away.
If it does, then connect the power wire and remove the brake light wire and see if you have a problem when you step on the brake. Some repro brake switches short to ground when the brake pedal is pushed.
Tom Wesenberg is offline   Reply With Quote
Old 06-01-2019, 08:08 PM   #20
Penthode
Member
 
Penthode's Avatar
 
Join Date: Oct 2016
Posts: 47
Default Re: Lighting dims question

As this thread has gone cold without any resolution and since my methodical approach has gone unnoticed, I thought a picture or two would take the place of a 1000 words.

There are clues in the original post which leads to the direction this should take. As a professional electrical engineer for nearly 50 years, I can point to the problem and it's resolution which should be quite simple to resolve if you follow the clues and apply a logical resolution process.

So let's first start with three clues.

1) the lights dim when the brake is applied.

2) Even when the brake is not applied yet the headlights are on, the horn gives a feeble "eeek".

3) The generator appears to provide a good charge.

Initial Conclusion:

1) The problem is not unique to the brake circuit because the same problem persists with the lights and horn only applied.

2) The generator appears to apply the correct charge. Also the battery is relatively new and does not appear to have been abused. There is no mention of any voltage or currents and so we can guess that the generator and battery are probably okay.

3) The problem therefore appears to be excessive electrical resistance in the path from the battery to the lights and horn.

The attached diagram with the wiring marked in red is the path from the battery to the common distribution point to the lights and horn. A high dc resistance anywhere along this path will yield the problem described. Because of the very low supply voltage involved (6 Volts) and the relatively high currents (4 amperes plus), the wire size must be of ample gauge to handle the current plus the connections must be excellent.

As I suggested earlier is to obtain a digital voltmeter and with the circuits switched on to demonstrates the fault, a table of voltage measurements can be made.

First put the meter across the battery terminals directly with everything switched off and take and record the reading. Then switch on the circuits which demonstrate the problem and measure the battery again. The voltage drop should be zero or very small indicating the battery is good.

Next, with the circuits switched on, measure directly from the positive battery terminal to the chassis. The voltage should be very small or near zero. If you measure 0.6 volts or more, then you have a battery connection problem at this point.

If the reading is near zero, with the circuits still on, measure the dc voltage at the cut out terminal to chassis. Compare the reading with the battery: if it is less than the battery by 0.5 volts or more, then there is a problem with the wiring between the battery negative terminal and the cutout connection including the ammeter resistance.

If the voltage at the cutout matches or is close to the battery voltage, then the problem lies down stream. A major culprit is the connection to the terminal I highlighted in yellow on the headlamp switch. Make sure the lugs are tight. The newer switched use slide on connections which are crimped. I had a problem here which I resolved by soldering the crimped connections.

Also dim incandescent 6 volt lamps is a symptom of using too small gauge wiring in the circuit. The wiring for 6 volt cars must be noticeable heavier in 12 volt cars. For the headlamps, I would even recommend 12 gauge wire from lamp switch to the bulbs and 10 gauge upstream. Anything less will raise high resistance and will lead to dim lamps.

To finish, the symptoms described point to a wiring problem between the battery and light switch.
Attached Images
File Type: jpg Ford Model A Wiring Problem.jpg (85.0 KB, 21 views)

Last edited by Penthode; 06-01-2019 at 10:22 PM.
Penthode is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Sponsored Links (Register now to hide all advertisements)


All times are GMT -5. The time now is 02:10 AM.