Mars

30 cf fuse size

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Hi, I know that I’ve asked this question before but I’m asking again. What is the fuse size for the cf. I think it’s 30 amp. I don’t know why I can’t find the answer anywhere. Thanks 

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Should not exceed the max amps of dash gauge and wire from ,and  generator . 20 or 30 amps is common . My BOI does not seem to list for my 31 Dodge either .

3 hours ago, Mars said:

Hi, I know that I’ve asked this question before but I’m asking again. What is the fuse size for the cf. I think it’s 30 amp. I don’t know why I can’t find the answer anywhere. Thanks 

 

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14 gauge wire would be no more than 20 amps and 12 gauge would be no more than 30 amps.

The instruction manual says where the fuse is but not the size. Schematic shows a fuse but not the amperage so you'll have to go by the wire size. 

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The fuse size on a 1930 DeSoto is 30Amp. It is mounted on the back of the ammeter. This fuse is meant to protect (or not protect!) all the wiring in the car. 

The fuse holder connection is fastened with a rivet connection to the back of the ammeter. Over time this connection starts to fail and heat up under load.

I have replaced mine with a modern fuse, as well as a proper fuse panel to protect the different circuits in the car. (ignition, gas gauge, dome light, horn, lights etc)

 I also installed a second tail/brake  light and installed a signal light flasher. 

The flasher signals the rear brake lights, and by using 6 volt relays I was able to use the single filament front fender lights for parking lights as well as signal lights.

Electrical systems were of poor quality and design in the early automotive years. The original DeSoto book does not talk of wire sizes, only "small braid, medium braid and large braid"

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Had same rivet loose problem on my amp gauge / fuse . Replaced rives with brass 4-40 screws and nuts ,from box stores  .Cleaned and added electrical anti corrosive to connections .

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Hi, I just finished installing a new wiring harness. Not too tough. But it isn’t getting a spark. I jumped the old fuse holder with a modern one. I’m wondering about the ignition switch. There  are 2 lugs. one says coil,one says ammeter. There was no mention of the connection between the switch and the coil - side. On the schematic it looks like there’s 3 posts on the switch. But it ran before I changed the wiring. When I turn the key on the gas gauge pegs to full. Horn works. No dash lights. I’ve gone over the new wiring and feel confident I have that right. Turns over ok. Really confused. Thanks for any help. 1930 DeSoto cf

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Got the dash lights working 

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Excuse me if you have mentioned this but are you still running 6v positive ground?

My ignition switch has three terminals but I have no idea if it is original and am guessing it is not. 

Do you have an original wiring schematic?

 

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Hi, yes, still positive ground. Yes, the wiring harness came with the original schematic showing wire colors and where they go. Rhode Island Wiring, excellent product. H

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Would it be possible for you to post the schematic here. It would help troubleshoot your problem. 

On my CF it shows the coil as part of the ignition switch.

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I’ll try. Yes, they show the switch and coil in one unit. Trying to figure that out. I think that’s the problem I’m having. It doesn’t show a wire from the switch to the coil, that I can figure out. Thanks for the help. Unfortunately I’m sitting in a hospital room right now.

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Posted (edited)

The ignition switch has the coil attached directly to back of if ,so connection is made thur a contact as you turn on .Wire in is from amp gauge and wire out is from coil to distributor . And hi voltage coil wire . If you have a two part system , like most  aftermarket set ups . You just break the power wire from gauge wire your ignition switch . 

  Hence wire from gauge to switch , switch to coil , coil to distr . .

 PS Get Well Soon !

Edited by ArticiferTom
PS (see edit history)

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Thanks, but I’m still confused. Isn’t that a coil under the hood? Like most cars. With a condenser and spark plug wire to the distributor. You’re saying that its not original? I’m confident that I have the new wiring harness correct. Do I need a new switch? No Covid 

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Need to see your wiring diagram . But  some mopars like my Dodge and others had the coil inside under the dash . This was a security measure and the wire to the distr,. was armored . Also the heat from engine did not cause premature coil failure . With the coil under hood you would only need jumper from starter (pwr) to coil and vehicle would start . But without a key to make hard contact between coil and ignition , nothing starts .

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Posted (edited)

I can't think of any reason why your wiring would have been different than mine when new. Mine was converted to a coil under the hood many years ago and the electrical system has been upgraded to 12v negative ground. 

That being said originally it appears that when new the ignition switch and coil were one unit under the dash. If yours now has the coil under the hood then you will have to run a wire from the ignition switch to the coil to power up the ignition system when the key is turned on. 

Edited by Fossil (see edit history)

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