The Ford Barn

Bob Grieb · 06-08-2012, 05:15 PM

I have a problem with the dash light wiring that has me baffeled. I have a 12 volt negative ground system and I connected the dome light lead to the ignition switch. When I turn the ignition switch to the "on" position the dash light goes on but the ignition is shorted and the engine will not start. If I remove the bulb from the dash light the engine will start. I do not understand what is happening to cause the light to short the ignition. Any ideas???

Thanks

Bob

Tom Wesenberg · 06-08-2012, 05:27 PM

Since the ignition switch connects the coil primary to the POINTS, you don't want to connect anything to either side of the switch, or it will mess with the function of the points and condenser.

newshirt · 06-08-2012, 05:28 PM

It sounds as though the light is wired in parallel with the ignition points. So when the points open, the light saps all the voltage so the coil cannot generate enough voltage for the spark plugs. In other words, the voltage going into the primary side of the coil is about 1 or 2 volts. That's not enough to generate the high voltage needed for the spark plugs. Check your wiring against the Model A wiring diagram.

You beat me to it, Tom!

CarlG · 06-08-2012, 05:35 PM

If you want to control things with the ignition switch, get one of the switches that has an ACC terminal available from the vendors.

Bob Grieb · 06-08-2012, 05:55 PM

In looking at the wiring diagram in the Les Andrews Manual it shows that the connection of the light wire should be connected to the ammeter. I will go try that. I did not think it would make a difference.

Bob Grieb · 06-08-2012, 06:32 PM

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I connected the dash light wire the the ammeter and the light is independent of the switch and on full time . I think I am going to have to put a separate switch to control the light. I thought from the diagram I could controol it with the ignition switch.

newshirt · 06-08-2012, 06:41 PM

Quote:

Originally Posted by Bob Grieb

I connected the dash light wire the the ammeter and the light is independent of the switch and on full time.

Can you twist the dash light housing to turn the light on and off?

Bob Grieb · 06-08-2012, 07:44 PM

Quote:

Originally Posted by newshirt

Can you twist the dash light housing to turn the light on and off?

The dash light has no switching capability. I may have to put a switch in the circuit. Aside from getting an ignition switch with an accessory pole I see no other way to control the light in its present configuration.

Thanks for your help

Bob

Bob Grieb · 06-08-2012, 07:46 PM

Quote:

Originally Posted by Tom Wesenberg

Since the ignition switch connects the coil primary to the POINTS, you don't want to connect anything to either side of the switch, or it will mess with the function of the points and condenser.

Thanks - I now know that. I just did not anticipate that it would be an issue.

Bob C · 06-08-2012, 08:04 PM

What instrument panel light do you have, the one in the center of the panel or the one
above the panel? They both have built in switches unless it is some kind of aftermarket.

Bob

Tom Wesenberg · 06-08-2012, 08:09 PM

Every Model A dash light has a switch if it's an original part. I've never seen one without the switch. If you have the dash light in the center of the instrument panel then it turns off and on by twisting and lightly pushing in or pulling out. If your dash light is mounted up higher, under the dash rail then it should have a round lever for the switch. Do you have the Service Bulletins, or Judging Standards? I'm sure it is shown in each and should also be in the Owner's manual.

Bob Grieb · 06-08-2012, 09:35 PM

I have a light that is mounted in the center of the panel over the oval speedometer. The light that I have does not have a switching capability. It was in a box of parts when I bought the truck. I now plan to buy an aftermarket light with a built in switch. Until I made this post I did not know that the light should have a built in switch.
Thanks
Bob
Thanks for all the help.

columbiA · 06-08-2012, 11:01 PM

On my late 30 coupe,I ran a wire from the lite switch up to the dash lite so that whenever the lites are turned on,the dash lite will come on.The D L switch is left in the on position. Since the D L is only needed when the lites are on,it seemed more practical to do it this way and it saves wear & tear on the D L switch.

Napa Skip · 06-09-2012, 07:22 AM

Wiring the dash light into the lighting circuit does seem more practical, although it also seems to interrupt the natural progression of things-to-fiddle-with while driving the Model A, starting with the spark advance lever on the left, the throttle control lever, the dash light and ending up with the gas adjusting valve on the (far) right. I have taken to driving my Model A with the headlights on, probably a "safety" carryover from more modern automobiles. Probably not needed inasmuch as the coupe seems to draw attention in and of itself ("Hey Ma, look at that old geezer driving that old car!" "Yeah, Pa, the old car appears to be in better shape than him..."). Since the "old geezer" has left the lights on one or two times after parking the "A" he now uses the dash light to remind himself that (duh!) the lights are on.

Bob Grieb · 06-09-2012, 08:20 AM

I can understand leaving the lights on after parking. I have added directional signals and I am always leaving them on. Although it does seem practical to wire the dash light into the light circuit I think I am going to buy a new lamp with a switch in it. That way it will take longer for the battery to discharge.

Quote:

Originally Posted by Napa Skip

Wiring the dash light into the lighting circuit does seem more practical, although it also seems to interrupt the natural progression of things-to-fiddle-with while driving the Model A, starting with the spark advance lever on the left, the throttle control lever, the dash light and ending up with the gas adjusting valve on the (far) right. I have taken to driving my Model A with the headlights on, probably a "safety" carryover from more modern automobiles. Probably not needed inasmuch as the coupe seems to draw attention in and of itself ("Hey Ma, look at that old geezer driving that old car!" "Yeah, Pa, the old car appears to be in better shape than him..."). Since the "old geezer" has left the lights on one or two times after parking the "A" he now uses the dash light to remind himself that (duh!) the lights are on.

Paul in Colorado · 06-09-2012, 09:54 AM

You can also wire the ignition switch between the ammeter terminal and the coil input, and connect the armored cable behind the instrument panel to another wire from the coil output. Be careful that you don't allow the armored cable shield to contact the connection. Then you can connect the dash light or the turn signals to the switch output.

Paul

jrelliott · 06-09-2012, 09:59 AM

Had trouble with the kids leaving the lights on when they started driving our '64 Corvair. Went to Radio Shack and purchased a LOUD solid state alarm, a relay and some diodes and hooked it up to the driver door switch for turning on the inside dome light and the ignition such that the alarm would go off if the ignition was off and the lights left on. Since we do not have these options on the Model A since it has no door light switch and the ignition switch only controls the points would be hard to design a circuit to give an alarm. May think on this for a while to see if can figure out a way to do it and will post if I come up with a way.

06-08-2012, 05:15 PM	#1
Bob Grieb Senior Member Join Date: Oct 2010 Location: Temecula, California Posts: 325	Dash Light - Wiring Problem I have a problem with the dash light wiring that has me baffeled. I have a 12 volt negative ground system and I connected the dome light lead to the ignition switch. When I turn the ignition switch to the "on" position the dash light goes on but the ignition is shorted and the engine will not start. If I remove the bulb from the dash light the engine will start. I do not understand what is happening to cause the light to short the ignition. Any ideas??? Thanks Bob

06-08-2012, 05:27 PM	#2
Tom Wesenberg Senior Member Join Date: May 2010 Location: Mpls, MN Posts: 27,582	Re: Dash Light - Wiring Problem Since the ignition switch connects the coil primary to the POINTS, you don't want to connect anything to either side of the switch, or it will mess with the function of the points and condenser.

06-08-2012, 05:28 PM	#3
newshirt Senior Member Join Date: Jan 2011 Location: Colorado Springs Posts: 868	Re: Dash Light - Wiring Problem It sounds as though the light is wired in parallel with the ignition points. So when the points open, the light saps all the voltage so the coil cannot generate enough voltage for the spark plugs. In other words, the voltage going into the primary side of the coil is about 1 or 2 volts. That's not enough to generate the high voltage needed for the spark plugs. Check your wiring against the Model A wiring diagram. You beat me to it, Tom! __________________ Ray White

06-08-2012, 05:35 PM	#4
CarlG Senior Member Join Date: Nov 2010 Location: Anchorage, Alaska Posts: 9,115	Re: Dash Light - Wiring Problem If you want to control things with the ignition switch, get one of the switches that has an ACC terminal available from the vendors.

06-08-2012, 05:55 PM	#5
Bob Grieb Senior Member Join Date: Oct 2010 Location: Temecula, California Posts: 325	Re: Dash Light - Wiring Problem In looking at the wiring diagram in the Les Andrews Manual it shows that the connection of the light wire should be connected to the ammeter. I will go try that. I did not think it would make a difference.

06-08-2012, 06:32 PM	#6
Bob Grieb Senior Member Join Date: Oct 2010 Location: Temecula, California Posts: 325	Re: Dash Light - Wiring Problem Sponsored Links (Register now to hide all advertisements) I connected the dash light wire the the ammeter and the light is independent of the switch and on full time . I think I am going to have to put a separate switch to control the light. I thought from the diagram I could controol it with the ignition switch.

06-08-2012, 08:04 PM	#10
Bob C Senior Member Join Date: May 2010 Location: So Cal Posts: 8,755	Re: Dash Light - Wiring Problem What instrument panel light do you have, the one in the center of the panel or the one above the panel? They both have built in switches unless it is some kind of aftermarket. Bob

06-08-2012, 08:09 PM	#11
Tom Wesenberg Senior Member Join Date: May 2010 Location: Mpls, MN Posts: 27,582	Re: Dash Light - Wiring Problem Every Model A dash light has a switch if it's an original part. I've never seen one without the switch. If you have the dash light in the center of the instrument panel then it turns off and on by twisting and lightly pushing in or pulling out. If your dash light is mounted up higher, under the dash rail then it should have a round lever for the switch. Do you have the Service Bulletins, or Judging Standards? I'm sure it is shown in each and should also be in the Owner's manual.

06-08-2012, 09:35 PM	#12
Bob Grieb Senior Member Join Date: Oct 2010 Location: Temecula, California Posts: 325	Re: Dash Light - Wiring Problem I have a light that is mounted in the center of the panel over the oval speedometer. The light that I have does not have a switching capability. It was in a box of parts when I bought the truck. I now plan to buy an aftermarket light with a built in switch. Until I made this post I did not know that the light should have a built in switch. Thanks Bob Thanks for all the help.

06-08-2012, 11:01 PM	#13
columbiA Senior Member Join Date: Nov 2011 Location: B.C. Canada Posts: 1,746	Re: Dash Light - Wiring Problem On my late 30 coupe,I ran a wire from the lite switch up to the dash lite so that whenever the lites are turned on,the dash lite will come on.The D L switch is left in the on position. Since the D L is only needed when the lites are on,it seemed more practical to do it this way and it saves wear & tear on the D L switch.

06-09-2012, 07:22 AM	#14
Napa Skip Senior Member Join Date: Mar 2012 Location: Napa CA Posts: 412	Re: Dash Light - Wiring Problem Wiring the dash light into the lighting circuit does seem more practical, although it also seems to interrupt the natural progression of things-to-fiddle-with while driving the Model A, starting with the spark advance lever on the left, the throttle control lever, the dash light and ending up with the gas adjusting valve on the (far) right. I have taken to driving my Model A with the headlights on, probably a "safety" carryover from more modern automobiles. Probably not needed inasmuch as the coupe seems to draw attention in and of itself ("Hey Ma, look at that old geezer driving that old car!" "Yeah, Pa, the old car appears to be in better shape than him..."). Since the "old geezer" has left the lights on one or two times after parking the "A" he now uses the dash light to remind himself that (duh!) the lights are on. __________________ Skip Keyser Napa Valley A's Olympic Vintage Auto Club (1980-1982) MARC of San Diego (1977-1978) MAFCA (since 1978) MARC (since 1977) ---------- Model A owners belong in their Model A’s; Model A’s belong on the road.

06-09-2012, 09:54 AM	#16
Paul in Colorado Senior Member Join Date: May 2010 Location: Arvada, Colorado Posts: 175	Re: Dash Light - Wiring Problem You can also wire the ignition switch between the ammeter terminal and the coil input, and connect the armored cable behind the instrument panel to another wire from the coil output. Be careful that you don't allow the armored cable shield to contact the connection. Then you can connect the dash light or the turn signals to the switch output. Paul

06-09-2012, 09:59 AM	#17
jrelliott Senior Member Join Date: May 2010 Location: Pine, AZ Posts: 794	Re: Dash Light - Wiring Problem Had trouble with the kids leaving the lights on when they started driving our '64 Corvair. Went to Radio Shack and purchased a LOUD solid state alarm, a relay and some diodes and hooked it up to the driver door switch for turning on the inside dome light and the ignition such that the alarm would go off if the ignition was off and the lights left on. Since we do not have these options on the Model A since it has no door light switch and the ignition switch only controls the points would be hard to design a circuit to give an alarm. May think on this for a while to see if can figure out a way to do it and will post if I come up with a way.