Brown wire, general electron health for Bertone question

Fiataccompli

Fiataccompli

Chris Granju
Okay, so I've read all the threads, the Wiki, and the various takes on a brown wire mod & general improvement on these cars. Now that I have the running/operating basics apparently OK on my '85 and I'd like to start wearing it out some, I suppose you could say I "care" more whether the electrical system works more or less like you may expect in an automobile. At the moment (and super-sporadic driving the last 9 months has done the battery no favors), it appears fine w/o headlights but night driving renders the voltmeter gauge at zero after a few minutes (no glowing light though) and in time I get the brake warning & the start of low low voltage type operation.

looks like a PO added a new 10(ish) gauge wire to the fuse panel (late style, modern fuses, relay for high beams), but I think nothing more.

Is it common or even helpful on the late cArs to add an additional 12v lead to the brown wire at the key switch?

I'm going to do some poking around this weekend. I will be adding a low beam relay. I added a ground strap from the head to the firewall & may add another ground from below. It seems that with any of the vintage Fiats you simply can't have enough of that...so hopefully that is helpful. I also made up a new ground cable from the battery using a rather huge cable...so effectively it may be more efficient than the frayed original + extra strap that it replaced. Would a solid copper wire for the ground be a good thing?

Thanks. I guess this is a case where there is so much good info that it almost becomes confusing...or maybe it's just confusing if you're me! Ha





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Relaying the headlights is going to help a lot with the voltage drop symptoms that you're getting with the headlights on - it will make the headlights-on behavior more like the headlights-off behavior.

If it is "fine without the headlights" adding more brown-wire paths will start showing diminishing returns, although it can't hurt. Likewise, once you have good battery-to-chassis and motor-to-chassis grounds, further work doesn't necessarily add much more.

One thing you could do after you've done the headlight relay:
With the engine running and the headlights on, check the voltage at the alternator output, at the common hot terminal on the starter, and at the battery positive terminal (use the battery negative as th eground reference, always). There shouldn't be a lot of voltage drop. Then check voltages at all the hot terminals in the fusebox - again, you don't want to see much voltage drop. Be particularly careful about circuits that are switched through the ignition switch; big voltage drops there suggest that the ignition switch contacts are overheating.
 
I agree about the headlight relay mod - I did it on my '82, removed the load from the ignition switch and it's great.

I also put my fan on a relay - what a HUGE difference in RPM (judging by sound, I will eventually use a tachometer & ammeter to quantify it).

:)


I have no BWM yet, but will do my version of it using large relays to take all the load off the ignition switch - and install the "white wire mod" which I use as an accessory position for the radio.

Cheers!
 
Thanks. That's a helpful algorithm. The fact that I appear to have a similar drop for the already relayed high beams as I do for the lows (though visually there's clearly a huge gap in voltage) is not what I expected. Going to explore this afternoon.


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Adding a relay to the ignition switch circuit will be a big help - it takes all the load off the switch and effectively takes nearly two yards of cable run out of the circuit. I used an OEM 50 amp Fiat relay for a factory look. The relay to the left of the 50 amp relay is for the low beam, which I added at the same time:



 
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I ended up with not much time at all over the weekend. running I was getting 13.7(ish)V at the battery, at the ign. switch, & at the + input to the fuse panel. With lights on (any lights), it dropped to 12.6(ish) and then begins to drop further, slowly. I was expecting a bit different behavior between hi/lo & parking lights. I educated myself a bit on the approach to checking voltage drops & will do so. I'm sure that cleaning grounds at all points is a wise thing...both front pods, at both rear lights...under dash?
 
Your malady sounds like poor/high resistance connections at the 4 way junction block bottom left of the fuse box, or at the battery. It is heating up and further increasing resistance.
 
Ah...well, that makes sense, that junction is replaced with 3 wires and a wire nut on this car. Between that point and the brown wire (switch side) at the switch I get a .13 v drop with lights on...but maybe more significantly, I'm also realizing the battery could be suspect as I just sat here idling with 13.8 V (no lights), turned it off and now I've got 10.5V on the battery. A bad cell could lead to this, right? More to check. Conveniently, the battery from my 124 Coupe is available to borrow for behavior comparison. I've been having to charge the battery in the Bertone, but I assumed it was an electrical issue killing the battery, not visa versa...likely some of both, actually.

Update: With lights, I get 12.12V at the alternator with 12V at the battery. And I picked up the same .12V or so checking various ground points between the alternator/block/lower ground strap and chassis & a startling bit more at one of he marker lights.

Grounds & connections to be cleaned next
 
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And, I should add, alternator must be compromised . The car could go rather indefinitely if I never need to use headlights, but that's an unlikely option. I found the wealth of information on hr 10si/20si GM alternator conversion which seems a likely way to go (even perhaps if all I have at fault here is a bad few diodes in the Bosch 65amp)
 
oh, oops...those last numbers were with a known good/new battery with a good charge...so just a bit over 12V with lights...11.7ish V with lights, hazards, fan & cooling fan...so I'm thinking a bit the opposite. Besides 12.15V at best coming out of it (B+ to case), it's fairly baked looking in general....which is something I'll need to consider with regard to the header already.
 
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