Brown Wire Mod??

If your car does not have air conditioning, could we use the hot terminals in the (unoccupied) relay sockets as BWM inputs?
Anyone?
 
One thing I'm not a fan of is how small the contacts are in the ignition switch. No matter how large of a BWM wire mod you have, the ignition switch is still bearing the brunt of conducting a lot of current.

What I plan on doing is installing 3 relays in total (2 larger ones, and one smaller 70A one for the start position) - all controlled by the keyswitch. This will take all of the load off the keyswitch. The BWM can go to the relay, and then back to the fuse panel. (I have an '82, and right now I can't recall what/where the wires go without looking at the schematic - but I can update if someone is interested). Anyhow, the OE keyswitch is a rare item these days and can be expensive. I know, it's a LOT of relays everywhere.. but it can improve reliability - if you use good relays.

:)
 
Resistance of a wire is a function of resistance per unit length and the overall length.
Exactly, which is why I say it is better than nothing. But depending on the wire gauge, the loss for even a short length of small gauge wire can be more than the difference over a longer length of larger gauge wire...if that made any sense. I guess my point being the whole lead isn't that long to begin with, so the gauge seems more important than the length...if that that was any better stated? But regardless it would be ideal to completely eliminate all of the undersized stuff. Also you might end up with a bit of a "hot spot" at the remaining piece of old wire.

Finding a better attachment point for the new larger power feed (at the box itself, rather than to the old wire before the box) is the best approach. I'd have to look at the actual layout/design to see if the idea "Jefco" suggests will work. Unfortunately I have AC, but I like the thinking. Maybe someday when I get one of my X's to that point I'll disassemble a fuse box and see what can be done.
 
What I plan on doing is installing 3 relays
I totally agree. Adding a bigger wire to the key switch is just a bandaid in my opinion. Reducing the load to the switch is definitely the answer. In my case I had to add a second power wire to the ignition switch because that white plastic 4-lead connector a few inches from it had melted and lost contact for the brown lead. So I replaced the entire connector with a 6-lead one and used two 'brown' (power) wires, each passing half the current through the respective contacts (of that connector). But that only fixed the failed connector, not the real problem. Actually, adding a heavier feed to the key switch may create a bigger problem by allowing more current to be carried by those tiny internal contacts you noted.

Adding relays to each of the larger draw components, with a separate add-on fuse box and heavier power source, will do the same as you suggest. That would include things like the starter solenoid, cooling fans, headlights, blower motor, power windows, wipers, AC, etc, etc. Like you said a lot of relays, basically a redundant wire harness. But the stock design was very undersized, especially after all these years and with any added upgrade equipment. If you were doing a complete restoration and stripping the car down to a bare shell, then I'd look at replacing the entire wire harness with a aftermarket kit utilizing a better fuse box and all other components. At SEMA I saw some amazing kits with very cool control panels.

On the subject of replacing undersized wires, don't forget to replace the tiny power feed from the alternator to the starter with a heavier cable. I've noticed lots of vehicles from that era had a smallish lead coming off the alt. Granted it does not get the direct draw as the other ones we are talking about, but it still carries quite a lot of current to recharge the loss created by everything. However the very long cable from the battery to the starter does get a very heavy draw, so it will definitely benefit from a heavier cable as well. That may in fact be the reason for a lot of starter issues.
 
I am a bit late to this but I got a lot of great information from this forum for the updates to the wiring. A few things that I noticed are that the conversion to LED headlights really cuts the draw so much that I may have not needed to do the Headlight relays but since I was also doing a big air horn and wiper mode along with the BWM I did it. I used a $15 relay and fuse box (amazon) on its own power for all the mods. As you can see from the image there is a Breaker (just using as a switch) that powers the fuse box through bus bars. The second power line off the breaker goes to another bus bar under the pass foot well near the fuse/relay box. All wiring was up-sized removing the 4way connector and new connectors near the ignition that allowed bigger wire right up to the key. I will replace the fuse box under the dash with a modern Lada version with blade fuses at a later date when the dash is out. I have replaced all light to LEDs which really cuts the draw. I notice that the biggest draw is raising and lowering the headlights.

fuse.jpg
 
I'm liking your re-routing of the speedo cable. It was kinda clumsy having to share with the three hydraulic hoses--it's practically impossible to pass that big cable connector thru without screwing something up!
 
I'm liking your re-routing of the speedo cable. It was kinda clumsy having to share with the three hydraulic hoses--it's practically impossible to pass that big cable connector thru without screwing something up!

The speedo was clicking when I got the car. Picked a new one and when I was removing the old one I could not believe how it was run. No wonder these things eat speedo cables. I drilled two new big holes and 3D printed grommets so now the run is smooth and no kinks or harsh bends.
 
I don't mean to carry this too far off topic, but in regard to the speedo cable routing. I also find it a bit odd how the cable snakes from the rear under the car, then into the tunnel, back out of the tunnel into the interior, back out of the interior into the bulkhead scuttle, back into the car under the dash...or whatever the route is (don't recall the exact path). But it sure seems like a lot of unnecessary in's and out's. I'll have to look at it again closer, but I hope to be able to carry it all the way from the rear to the frunk, either completely under the pan or in the tunnel - and not back and forth in and out. I'm also using the longer one-piece cable and eliminating the extra junction and mile counter box.
 
Last edited:
I don't mean to carry this too far off topic, but in regard to the speedo cable routing. I also find it a bit odd how the cable snakes from the rear under the car, then into the tunnel, back out of the tunnel into the interior, back out of the interior into the bulkhead scuttle, back into the car under the dash...whatever it is (don't the recall exact path). But it sure seems like a lot of unnecessary in's and out's. I'll have to look at it again closer, but I hope to be able to carry it all the way from the rear to the frunk, either completely under the pan or in the tunnel - and not back and forth in and out. I'm also using the longer one-piece cable and eliminating the extra junction and mile counter box.

I replace mine with a one piece. It ran from the back outside, only a grommet in the engine bay, all the way under the car to the entry by the Gas pedal and up to the firewall through my new hole, then back through my new hole to the speedo. Honestly the new cable through the new holes took 1/4 the time of pulling the old cable. I agree it is an odd way to run a speedo. It amazes me how well this little car is designed then you get to the speedo cable.
 
I replace mine with a one piece. It ran from the back outside, only a grommet in the engine bay, all the way under the car to the entry by the Gas pedal and up to the firewall through my new hole, then back through my new hole to the speedo. Honestly the new cable through the new holes took 1/4 the time of pulling the old cable. I agree it is an odd way to run a speedo. It amazes me how well this little car is designed then you get to the speedo cable.

If the factory order-of-assembly was speedo cable first, then hydraulic hoses, then it's not that big of a deal.

LOTS of cars were designed to be assembled in the factory with little priority assigned to ease-of-repair later in the field. Just ask ANY mechanic, they maintain a hate-list in their heads!
 
LOTS of cars were designed to be assembled in the factory with little priority assigned to ease-of-repair later in the field.
So true. Things like having to lift the engine up several inches just to change spark plugs, or drop the entire exhaust and lower the trans in order to service it, and soooo many more examples. Although I've avoided American vehicles as much as possible, in the limited exposure I've had they seem to be among the worst for such things.
 
I pretty much left the original wiring in place but instead of going to the actual headlights now the original wires power a relay. A new fused wire goes from the battery to the relay to the bulbs. the same wire feeds both the high and low relays but I used bigger wire than necessary.
 
The following isn't directed at anyone or any specific example - just general comments:
At the risk of sounding like a old man I'll remind everyone to use good practices when doing any wiring mods. The original harnesses are very marginal in my opinion; too small gauge, poor quality insulation (especially after all these years), very poor routing, little protection, inferior connectors, insufficient fuse utilization, etc. Don't make the same mistakes when creating new harnesses for any mods. If electrical work isn't one's strong suit, consider doing some research first. There are some good easy to follow tutorials in "DIY" books and online (lots on YouTube) available for free. For some reason wiring seems to the thing that always gets the worst work I've ever seen done on old cars, don't be that guy. ;)
 
Regan, you bring up a good point about the various BWM's.

Ideally the new larger gauge, heavier capacity power lead coming directly from the battery would connect directly to the main power terminal on the fuse box itself. However as you have found there isn't a convenient way to make that final connection on many of these wire harnesses/boxes. The fuse box does not have a big threaded terminal that the power lead connects to or something similar (as some other older vehicles have). So where/how do you splice into the fuse box? By making a splice into the existing wire (like the prior owner did to your car), it is only as good as that final few inches of original wire into the box. That will be the weakest link. Granted it is still better than no additional wire, but the current must still pass through the smaller gauge wire for that final short stretch. Sort of like increasing the water pipe diameter throughout your house but not the increasing the size of the main shutoff valve (that may be a bad analogy, I'm not a plumber, but hopefully you get the idea).

The same is true for the wire upgrade at the ignition switch. Adding a new larger gauge power feed to the switch, but not being able to connect it to the actual terminal in the switch. Instead having to splice into the existing smaller wire somewhere near the switch. Better than nothing, but not ideal.

I suppose the only true solution might be to replace the entire fuse box with a better design, and same for the ignition switch. And some have done that. But most of us do not want to go that far. I guess the best we can do is make our best effort to improve the power feeds to the critical components in the best possibly way. And that may mean splicing into the original wire as close as possible to the final component. For such a wire splice, a soldered connection might be good (although some prefer crimp connections for everything). Personally I remove the existing original wire and splice my new large gauge wire to the little pigtail I've left at the fuse box. But some prefer to leave the original wire and add the new lead as a second feed to that point. It might depend on what gauge of new wire you choose.

If you wish to connect multiple main power feeds - i.e. a large gauge wire from the battery, a large wire to the ignition switch, and a large wire to power an auxiliary fuse box (for additional circuits and relays), then maybe consider using some sort of buss bar or power terminal. Here are a couple examples:

View attachment 27923 View attachment 27924

And at the battery post you have a few options:

View attachment 27925 View attachment 27926 View attachment 27927 View attachment 27928

One method I like to use for the battery is installing a side post battery (with the threaded holes rather than large posts) so I can bolt several battery cables onto the same point (using cables with a eye ring lug on the end instead of a clamp). But the "marine" type of top post clamp with the threaded stud and wing nut (bottom left image) will do the same.
Which of these (your original pictures) would be your preferred terminal? I need to add a fourth connection to my positive post, and figured it was time to clean up and improve what was there when I got the car, which Carl says was a "sad assemblage". Excellent verbiage I thought. Here's what Autozone had this morning:

8445630B-A124-4F6E-A041-B1FB14B46A46.jpeg
 
Which of these (your original pictures) would be your preferred terminal? I need to add a fourth connection to my positive post, and figured it was time to clean up and improve what was there when I got the car, which Carl says was a "sad assemblage". Excellent verbiage I thought. Here's what Autozone had this morning:

View attachment 48392
I would not use the one on the left, it is designed for a different purpose than adding cables. The one on the right may work but I'm not sure what gauge of cables it is made to add. I think for a top post battery the simplest one to use might be the original "marine" style like this:

81txZm+8HcL._AC_SL1500_.jpg

You should be able to find them at many parts sources. And they are not expensive like some of the others are. However you will need to either replace your existing cable with a "ring terminal" one, or cut off the existing end and add a ring terminal:

6d7cf9c63f0.jpg

"Google it" to see how that is done, there will be lots of YouTube videos for you to watch. :D
 
I haven't gone back to view the entire thread so did not see what was there. In that case it needs to be redone. But not difficult with the right tools.
It looks like hell, but surprisingly, all the cables are very snug in their post rings, and securely attached to the post. Still looks like hell though…
 
Back
Top