Electrical issues

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Cisco82
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Electrical issues

Unread post by Cisco82 » October 11th, 2020, 8:32 am

Hi fellows,

my restorations project is in progress (A1 model)and im intalling a refurbished electrical harness , i have two doubts:

1- Where should i connct the wire linked on the back of instrument panel plate? i suppose it is the ground but i heve no idea where to connect it ...

2- Whrw shall i connect the wire 77B , i suppose it is a ground cause ut has a eye connector , it is a long wire ... maybe to teh fuel tank??

Thanks for ur advice

BR

Francesco
Francesco

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Alfa Romeo AR-51 1952

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Re: Electrical issues

Unread post by rickf » October 11th, 2020, 9:54 am

77B goes to the starter post, that gives the fuel pump power while the starter is cranking. The wire on the back of the dash panel will need to be grounded to the body. If you are working with an A1 wiring harness you will not have a connection for that wire. That is an A2 dashboard probably, You could get a connector that plugs into one of the ground connectors and adds a second receptacle for that plug. That is the cleanest and most accurate way of doing it. The dashboard should be grounded by the mounting screws just like all of the older A1 styles until you find a way to connect that wire so don't worry too much about it.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

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Re: Electrical issues

Unread post by Cisco82 » October 11th, 2020, 3:01 pm

Got it.

Thanks

Francesco
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Re: Electrical issues

Unread post by Cisco82 » October 11th, 2020, 3:22 pm

Fellows,

i have another issues ... id like to remuve the big circuit brackers with new ones ... but im not sure about the size...

I know the original ones are 15 amp and it works at 24 v , so if i find a CB for 12 v car should i buy a 30 amp CB?

Thx
Francesco

M151-A1 1969
Alfa Romeo AR-51 1952

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Re: Electrical issues

Unread post by Mr. Recovery » October 11th, 2020, 8:12 pm

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Re: Electrical issues

Unread post by Cisco82 » October 12th, 2020, 2:46 am

Thanks i know they are easly available but for some reasons i d prefer to use the small in line ones , it is the reason why i was wondering of i should buy a 12v 30 amp CB to substitute the original 24 v 15 amp CB.

I m not an electrical specialist so id appreciate a feedback.


Thanks for your support

Francesco
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Re: Electrical issues

Unread post by rickf » October 12th, 2020, 9:11 am

I don't understand why you would want to use a one time use fuse over a auto reset breaker but if that is what you want to do send a PM to George from Holland, He is an electrical wizard and would be the best to answer your question. Below is his info.

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1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

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Re: Electrical issues

Unread post by Cisco82 » October 12th, 2020, 1:02 pm

thanks
Francesco

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Alfa Romeo AR-51 1952

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Re: Electrical issues

Unread post by Redlight » October 12th, 2020, 7:37 pm

Greetings,
Fuses are very different than circuit breakers. Fuses will interrupt the power once as the internal wire overheats and melts. A Circuit Breaker (CB) is designed to open/trip with a higher than designed flow of electricity. A CB can be reset ether automatically when amperage is removed and it cools down, or manually via a button or handle. Both are rated for voltage and amperage. Usually they can stand higher voltage with out damage. They are rated for voltage on the case or on the box. When the voltage is too high, then damage occurs but it usually will pass power.
The limiting factor is the amperage through the device. So the key is to only use the amperage rating to choose the device. It would not be a wise choice to use two 15 amp devices in place of a single 30 amp device. When you combine the two devices, the load is not shared equally and one or the other will open and cause the other to fail as well. They are not power devices IE rated for combination of volts and amps but a really rated for flow/current.
I hope this makes some sense,
Thanks
Bruce

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Re: Electrical issues

Unread post by Cisco82 » October 14th, 2020, 4:28 pm

Thanks for explanation but i think it was a misunderstanding....

I was asking about 30 amp instead of 15 amp cause i suppose the fuse was designed for power (Watt = A x V) and i thought typical fuse is designed for 12 v system ... now it is claear to me they are designed for tipically 28-32 v so i ll choose a 15 amp one (same of original CB)

Thx

Francesco
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Re: Electrical issues

Unread post by Redlight » October 14th, 2020, 5:23 pm

You got it. Buy based on amperage.
Good luck

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Re: Electrical issues

Unread post by Cisco82 » October 21st, 2020, 2:54 pm

Hi again fellows,

i m again into problems ... i m getting crazy and i need you advice...

I installed the restored wiring harness and my idea was check all the funtions (light , fuel pumps, direction indicator, ...) before installing the engine.

I connected the batteries and when i swich on the ingnition swich i was sure to hear the fuel pump starting but ... nothing ..

I check the power and i find 24 volt on the wire 5 (the small one connected to the starter foot swich) but i cant find power on wires 11 that are connected to the ingition switch... even if i try to check if wire 5 and wire 11 are linked the result is they are not linked...

To be honest i cant understand ... regulator and generator are not isntalled , but i think it is not a problem...

Thanks in advance for your advice

Francesco
Francesco

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Re: Electrical issues

Unread post by rickf » October 21st, 2020, 3:22 pm

Do you have the #5 wire hooked to the same wire on the foot switch as the one COMING FROM the battery? That is the wire it needs to be hooked to. The other side will only be hot while cranking. In addition, IF you have an A1 wiring harness in there and it is all hooked up correctly with the #77 circuit going through the oil pressure safety switch then the fuel pump will not run just when the switch is turned on. The only time the pump will run is when the starter is cranking or when you have more than 10lbs. of oil pressure.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

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Re: Electrical issues

Unread post by rickf » October 21st, 2020, 3:24 pm

Keep in mind that all of my diagnosis and advice is based on a stock wiring harness that is properly installed. You have modified the harness with different fuses so I can only assume that is all in order. An A1 has three breakers and an A2 has only two breakers. An A1 has the #77 fuel pump circuit and the A2 does not have that circuit. The #77 circuit is the extra breaker in an A1 harness. Tell us exactly which wiring harness you are using and if you have the safety switch in the circuit or not. I can tell you how to make it work either way but I need to know what you are working with.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

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Re: Electrical issues

Unread post by Cisco82 » October 21st, 2020, 3:52 pm

Yes , the wire 5 is linked to the wire 6 coming from battery .

I have a A1 harness , and yes i have used 3 fuses instead of 3 CB , i can reinstall CB it is not a problem ...
Francesco

M151-A1 1969
Alfa Romeo AR-51 1952

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