The Ford Barn

Russell Reay · 06-19-2022, 06:27 PM

As I continue my assembly process, is there a need to assure good ground from the sheet metal cowl and dash rail to the frame/ battery? In 'modern' cars there is a never ending need to ground light sockets and accessories to the sheet metal, and light-weight ground straps are usually used to connect the body to the frame. As I review model A wiring diagrams and ponder all the possibilities I can't think of a need to ground anything to the sheet metal. Comments please.

GRutter · 06-19-2022, 07:13 PM

Good grounds never hurt anything.
The dash light, interior lights (if equipped) and cowl lamps (if equipped) depend on a good body ground.

PC/SR · 06-19-2022, 08:21 PM

A simple grounding strap from the battery to the sheet metal body helps the lights grounds. Run the battery primary ground to a bolt on the transmission. Helps with the starter. The cowl/dash is adequately ground by the bolts.

Kevin in NJ · 06-20-2022, 07:09 AM

Use the original fuel system and you are fine.

Your ground paths are the body bolts at the cowl and the fuel line.
Make sure that some paint is cleared around the body bolts if you put it on thick and use the original fuel system and you are more then good to go.

You have very little current flowing as it is only for lights. Horn is grounded to the frame by the steering gear. So it is kind of hard to mess up and you should not need any extra ground straps, unless you have a lot of bondo where the bolts go.

Russell Reay · 06-20-2022, 07:32 AM

Never thought about the grounding thru fuel lines--cool. No bondo around the body bolts, but will scrape away some paint before final tightening.

CT Jack · 06-20-2022, 07:55 AM

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The main items for good electrical grounding on the Model A is to install a heavy gauge ground cable from the battery to the frame. A 2nd cable should electrically connect the engine assembly with the frame. This is done by running a wire from a bellhousing bolt to the frame. The technical reason for doing this is the engine is mounted on rubber pads and therefore, theoretically could occasionally be isolated from being grounded. Even though this is a remote possibility, running a ground strap from the engine to the frame prevents this from ever happening.

rotorwrench · 06-20-2022, 08:51 AM

It doesn't hurt anything to install bonding straps but most components are already bonded due to bolt up connections. If a person installs a full float a motor mount kit then that may tax an engine to frame bond but the original is bolted in several places. The wood body cars built by subcontractors like Murray and Briggs may need more bonding in places but even they have metal braces inside. The major current draw items like the headlamps & horn are all bolted to the car through a series if braces, supports, and sheet metal connections.

If the car has been in the elements for many years and has a lot of corrosion then the band aid fix would be adding bonding jumpers. If all the corrosion is removed and the metal is clean and well bolted together then bonding should be as good as Ford intended. If you have fiberglass rear fenders then a bonding jumper for the tail lamps may be needed for the tail light/lights.

Ed in Maine · 06-20-2022, 02:42 PM

I have found that one area that helps a lot to ground separately is the headlights. When I rebuild a head light, I run a separate ground wire (16 AWG, a small diameter wire) out the bottom where the mounting bolt is located. Use a stranded wire and crush it to a cleaned head light bar. Then run another wire down the fender support bracket and pick up a good ground in the engine compartment. These modifications will give you the best lights possible.

06-19-2022, 06:27 PM	#1
Russell Reay Senior Member Join Date: May 2021 Location: NH/ VT Posts: 334	Does the cowl need to be grounded? As I continue my assembly process, is there a need to assure good ground from the sheet metal cowl and dash rail to the frame/ battery? In 'modern' cars there is a never ending need to ground light sockets and accessories to the sheet metal, and light-weight ground straps are usually used to connect the body to the frame. As I review model A wiring diagrams and ponder all the possibilities I can't think of a need to ground anything to the sheet metal. Comments please.

06-19-2022, 07:13 PM	#2
GRutter Senior Member Join Date: Sep 2017 Location: Mint Hill, North Carolina Posts: 386	Re: Does the cowl need to be grounded? Good grounds never hurt anything. The dash light, interior lights (if equipped) and cowl lamps (if equipped) depend on a good body ground.

06-19-2022, 08:21 PM	#3
PC/SR Senior Member Join Date: May 2010 Location: Santa Rosa, CA Posts: 1,278	Re: Does the cowl need to be grounded? A simple grounding strap from the battery to the sheet metal body helps the lights grounds. Run the battery primary ground to a bolt on the transmission. Helps with the starter. The cowl/dash is adequately ground by the bolts.

06-20-2022, 07:09 AM	#4
Kevin in NJ Senior Member Join Date: May 2010 Location: South East NJ Posts: 3,398	Re: Does the cowl need to be grounded? Use the original fuel system and you are fine. Your ground paths are the body bolts at the cowl and the fuel line. Make sure that some paint is cleared around the body bolts if you put it on thick and use the original fuel system and you are more then good to go. You have very little current flowing as it is only for lights. Horn is grounded to the frame by the steering gear. So it is kind of hard to mess up and you should not need any extra ground straps, unless you have a lot of bondo where the bolts go.

06-20-2022, 07:32 AM	#5
Russell Reay Senior Member Join Date: May 2021 Location: NH/ VT Posts: 334	Re: Does the cowl need to be grounded? Never thought about the grounding thru fuel lines--cool. No bondo around the body bolts, but will scrape away some paint before final tightening.

06-20-2022, 07:55 AM	#6
CT Jack Senior Member Join Date: May 2010 Location: Hebron, CT Posts: 432	Re: Does the cowl need to be grounded? Sponsored Links (Register now to hide all advertisements) The main items for good electrical grounding on the Model A is to install a heavy gauge ground cable from the battery to the frame. A 2nd cable should electrically connect the engine assembly with the frame. This is done by running a wire from a bellhousing bolt to the frame. The technical reason for doing this is the engine is mounted on rubber pads and therefore, theoretically could occasionally be isolated from being grounded. Even though this is a remote possibility, running a ground strap from the engine to the frame prevents this from ever happening.

06-20-2022, 08:51 AM	#7
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,425	Re: Does the cowl need to be grounded? It doesn't hurt anything to install bonding straps but most components are already bonded due to bolt up connections. If a person installs a full float a motor mount kit then that may tax an engine to frame bond but the original is bolted in several places. The wood body cars built by subcontractors like Murray and Briggs may need more bonding in places but even they have metal braces inside. The major current draw items like the headlamps & horn are all bolted to the car through a series if braces, supports, and sheet metal connections. If the car has been in the elements for many years and has a lot of corrosion then the band aid fix would be adding bonding jumpers. If all the corrosion is removed and the metal is clean and well bolted together then bonding should be as good as Ford intended. If you have fiberglass rear fenders then a bonding jumper for the tail lamps may be needed for the tail light/lights.

06-20-2022, 02:42 PM	#8
Ed in Maine Senior Member Join Date: May 2010 Location: Washington Cty., ME or Flagler Cty., FL Posts: 1,106	Re: Does the cowl need to be grounded? I have found that one area that helps a lot to ground separately is the headlights. When I rebuild a head light, I run a separate ground wire (16 AWG, a small diameter wire) out the bottom where the mounting bolt is located. Use a stranded wire and crush it to a cleaned head light bar. Then run another wire down the fender support bracket and pick up a good ground in the engine compartment. These modifications will give you the best lights possible.