Thoughts on adding relays

[wikkid]

It all started innocently enough. I replied to a post about adding a pushbutton into the ignition circuit here. I mentioned it might be good to get the high current flow out of the fairly fragile ignition switch, and someone asked me how.

Well, I'm not an electrical guru or even an engineer, and I don't even play one on TV, but it got me thinking nonetheless.

What if one were to run a new wire direct from the battery alongside the original feed? All connections would stay the same: the starter, the alternator and the brown wire to the ignition switch. However, instead of passing full load through the brown wire and through the switch, the wires connected to the switch would become the trigger wires to relays (connect to 85 point, with 86 to ground). Then, that new wire you just ran from the battery would connect to the 30 connector on the relays, with the 87 contact wire going out to power the electricals on the car.

With all the zigzag paths along which the current flows in a Spider, it's obviously not as simple as that. I mean, you have turn signal power flowing through the hazard light switch; you have flow through the ignition switch and the steering column switches... so more study of the wiring schematics would obviously be in order.

Maybe my ideas for actually carrying out this idea are all wrong, but as a concept, wouldn't it make sense to take the load off the ignition switch in these cars, and use relays for exactly what they were meant to do?

[majicwrench]

Sure, that could be done, but really there is no reason -IMO- to add all that compexity to the vehicle. Ign switch designed to do what it does, carry an electrical load.

[gchocevar]

Hi,

I've read the forums about dim headlights because of the current through the ignition switch. Th electrical drawings on my 79 actually confirm that. Why would they put in a horn relay and not a relay for the low beams and hi beams?

I also thought about running a separate wire from the battery but I am going to take the forums suggestion on my 79 another way. The brown power connector is just below the steering column with an extra stab. I have a power window relay socket and seat belt relay under the glove compartment that is already unused. A little rewiring under the dash should do the trick.

[wikkid]

I read somewhere here that it appeared Pininfarina added headlight relays to the spiders, in which case I would have those (1984). But I haven't looked yet, as I am still working on more basic things. The power windows will need some serious help, however, even though they are fitted with relays already. How weak can you make a motor, seriously?!!
I'd like not to have to change much at all, so I am going to tread very carefully, but when it comes time, I will be running extra wire runs from the trunk to the front - just in case. Just good insurance.

[spider2081]

I don't know anyone who has added the relays that is disappointed with the circuit that was modified. Some put the relays on the drivers fender well near the alternator some put them near the ignition switch. I prefer the engine compartment near the alternator. I have relays control the headlights, radiator fan and the starter solenoid.

[jimincalif]

I've installed headlight and starter solenoid relays. Best (and most cost effective) mods I've done. Lights are bright and starter cranks every time.

[james124]

I've installed headlight and starter solenoid relays. Best (and most cost effective) mods I've done. Lights are bright and starter cranks every time.

Hey Jim. Could you explain how the relay on the starter solenoid is set up. I would really like to do that mod. Should save the ignition switch too! Thanks for your help. JimmyG

[wikkid]

james124, here is a good thread with two options for wiring in a relay:
http://www.fiatspider.com/f08/viewtopic.php?f=6&t=11740

[eddie124]

Hello guys,

Just as an aside to this topic, you could add relays to pretty much anything, yes, but you'd end up with a parallel wiring loom - why bother?

There's also the risk that a clumsy setup might increase the risk of electrical mishaps. I've recently broken up a Fiat 125 that fell victim to an engine compartment fire which started on a cluster of relays added by someone who didn't take all the care they should have with the proper insulation of the terminals. Add clumsy wiring and fuel spray from a loose carb connection and you're there... barbecue time!

Having said this, there are some things where it makes sense to have relays, like halogen lights which draw much more current than stock. Early european cars sometimes had a relay for high beams, I remember my BC Coupe having this, plus my '74 CS1 Spider too. I think the '68 AS I restored a few years back also had this, but can't be sure.

My favourite method is to set the whole lot by the fuse box, drawing the lines from the original setup going into the respective light fuses (there's one for each side and beam) and putting them as triggers for the relay. Then the outputs from the relays go back to said fuses. I usually take power from the accessories plug feed, which is a redundant part of the loom (when did you last see an original Fiat accessory for this plug? Exactly...), and it's done. Simple, really, and not very visible at all.

About the starter relay, be careful as you'll need a proper high-capacity relay as the solenoid needs quite a bit of juice, if you use a plain one it might burn out very quickly.

And most sacred of all rules, NEVER use an unfused feed from the battery. And insulate all the terminals while you're at it.

Cheers, Eddie

[baltobernie]

Good points, Eddie.
I would add that users need to know the function of all the pins on the relays they're using. One of the most popular "ice cube" relays used for the last 50 years has a terminal that is "hot" when the circuit is "off". Not insulating or removing this terminal is like dangling a live bare wire in the engine compartment.

To recap: the Spider electrical system is not particularly failure-prone. The design was contemporary for the period. Two ... no three things conspire to making your car a Murphy-magnet:
1. PO's that have chopped, cut, sliced and diced every wire they could reach in futile attempts to circumvent or "repair" an electrical system for which they didn't own a manual or didn't know how to read it. Spiders were never "collector" cars, and were rarely treated to the same level of professional repair their Italian siblings were.
2. Rust. As in corrosion to grounding points and connectors.
3. Less-than-optimal ignition switch schematic. Again, not much different from its contemporaries, but not likely to last 30, 40, 50 years, particularly in a roadster. Fiat chose to run headlamp current thru the ignition switch, and this is a bad idea. If you modify a good ignition switch to operate only the circuits that a typical American car uses, you won't have any problems.