Some Fiat Electrical Basics: Part 2, Implications for use of a Lada ignition switch

[zachmac]

NOTE: I take no responsibility for work you or someone else does on you car and the results. I have taken every precaution I can think of to get all this right but I cannot control the actions of others.

Hopefully you’ve read and understood the first post in this series. If not it is highly recommended you do that first. I broke it into several posts because I knew it would be long and the first part should be helpful to all, regardless of whether they have an original ignition switch or are wiring a replacement Lada switch.

I was reluctant to give up my original SIPEA ignition switch as they are generally not available now or very expensive and the Lada replacements are reported to be short lived. That said, after failing to repair my switch using the excellent write up on Mirafiori on the subject (even though I did it for a friend a few years ago successfully), I was really left with no alternative but the use of a Lada switch. I received it from the vendor I prefer and immediately set about checking how the various connections on the back matched or differed from the stock unit both physically and electrically.

Physically the differences are in the number of each post. At least in my case (1978) my stock switch had two #30 posts (brown wire), one #30/1 post (black wire), one #50 post (red wire), one 15 post (Pink wire) and two center INT posts (BL/BK, blue with black trace wire). Different year cars will have some different number of these but will have at least one of each. Some may also have a sixth #16 post but mine did not. The use and electrical connections between these is explained in Part 1 of this series.

The Lada switch (I understand there are a few variations being sold) I received had one #30 post, one #30/1 post, one #50 post, a two prong #INT post, and one #15 post. It has four key positions, Locked (key in or out) marked “III”, OFF (key in) marked “O”, RUN marked “I”, and START marked “II”.

Electrically it differs from the stock SIPEA switch in a significant way. It is still comprised of two circuits internally, one for the #30 / INT / #50 post set, and a second for the #30/1 / 15 post set. The #30/1 / 15 post set works the same as the stock switch; powered in RUN or START, otherwise not powered. The #30 /INT / #50 post set however works differently. It passes power between #30 post and INT posts in RUN, START AND in Locked / key removed (but not in OFF). It operates the #30 / #50 connection the same as the stock switch, connected only in spring-loaded START position.

On this surface this would tell you that you should NOT wire it like the stock switch as that would now mean the loads powered by the BL/BK (blue with black trace) wire from the INT post will also be powered when you shut off the car and remove the key!
I assume this is what the vendors considered as well as they suggest wiring the switch as follows:

“Brown to INT post” (I assume they choose the INT as it look more robust even though it is electrically identical to connecting the brown wire to #30 post as per the stock wiring)
“Red to #50 post” (same as stock)
“Black to #30/1” (same as stock)
“White AND Blue to #15“ (same as stock for white that replaces pink but different for BL/Bk wire)

What this in effect does is make the switch work like the original in that none of the switched loads are powered in OFF or Locked / key out and all are in RUN or START.

Why do I think this is bad?

While this configuration will work, it has, in my mind, a flaw. It leaves as the ONLY function of the large gauge brown wire feeding the starter while cranking. ALL other power now routs from the smaller gauge black feed through a single set of contacts in the ignition switch to the loads. I believe this may be a cause of premature failure of these switches many have experienced?

In any case, it is NOT NECESSARY. If you read and recall Part 1 of this series and you looks at your wiring diagram you’ll see that the loads that are normally powered by the Brown wire when in RUN are what I called the Switched (Situational Needs) loads. That is they are all loads that only use power when a second switch in the circuit is actuated by the driver. Therefore I recommend wiring the Lada switch exactly the same as the stock switch. The results will be:

1) In run or start the switch will operate exactly the same as always BUT power to the loads will still be divided between the Brown and Black feed wires / circuits.

2) Yes, when you turn the car off and remove the key, power will also still be “ON” to the Switched (Situational Needs) loads making them basically act like UNSWITCHED loads. But they are still fused and still controlled by a second switch. If you just make sure you don’t leave the headlights / wipers / heater blower motor on you’ll be fine. I think this is better than running all the power through half the switch!

3) Lastly, due to the quirky fact that with the key inserted and turned to the O position the Lada switch breaks the #30 to INT connection, when you park the car at home (assuming in a garage) or in your sight (outdoor café) you can just leave the key in the ignition in O and you are right back to the same electrical state as a stock switch with the key removed (without of course the locked steering wheel component).

So, these are my thoughts. I’ve wired my car this way and so far so good. Any comment or corrections to what I’ve written are of course welcome. I believe wiring it this way should extend the switch life and the change in the status of some circuits from switched to unswitched when the car is locked / key is removed is manageable.

Lastly, none of this should dissuade you from moving as much of the power off the ignition switch as you can by changing loads like the headlights or wipers, etc, to relays passing only trigger power through the switch.

[wetminkey]

I can attest to the fact that my ignition switch replacement, wired exactly like my old original, resulted in continuous power to previously unpowered leads in the fusebox,...I could not understand it and intended on troubleshooting at a later date. Now I understand why!
Better yet,...I ALSO now understand that I can leave the key in the switch, in the "O" (OFF) position, and disable those circuits!
Holy Smokes!
Gosh, zachmac, ya just saved me from a lot of time troubleshooting under the dash!!
Nice write-up, thank you! This will benefit the forum,...
Todd Compton.