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Re: 1975 124 Spider 8 Relays?

Posted: Tue Jul 23, 2019 7:16 pm
by spider2081
I'm fairly certain they were all always mounted upside down.
I'm sorry I was not clear in that statement: " I have seen a number of spiders with the fuse panels mounted upside down." What I was thinking was that fuse #1 (identified by the color of the wires on it) was closest to the door jam not the steering column. I believe the factory installed the feed wires to the top of the fuse panel and the load wire to the bottom. The top (feed) has a single spot for a single wire to connect to a given fuse and the bottom (load side) has 2 spots where wires may be connected, one above the other. Also most of the fuses are paired example 3&4 5&6, 7&8, 9&10 the jumper bar is internal to the fuse panel and is visible looking into the fuse panel with the fuses removed. It connects the top (feed) fuse contacts.

I believe the fuses single wire terminals belong on the top and the double wire terminals belong on the bottom when the fuse panel is mounted per the owners manual.

Now I could be confusing myself LOL

Re: 1975 124 Spider 8 Relays?

Posted: Wed Jul 24, 2019 12:33 am
by kendall
I understand now. The ignition switch is the signal to the relay to allow the fan to see power. And then the thermal switch in the radiator will complete the circuit when the fan is needed. Also, sounds like I should inspect the wiring colors on my fuse box to be 100% sure I have it the right way.
friedman wrote:
Tue Jul 23, 2019 8:39 am
I have a 75 spider project and if you are really motivated you can remove at least four of those relays as they have to do with emissions equipment.
I don't have to smog this 75 in California, so I am all ears about simplifying what is going on with the engine. Which ones can be removed?

Again, thanks for all the info everyone.

Re: 1975 124 Spider 8 Relays?

Posted: Wed Jul 24, 2019 7:42 am
by friedman
The factory shop manual has a page that shows the location and function of all the relays in the car. If I get a chance I'll post a description and what I did with each of those 10 relays. I believe I'm using only one now.

Re: 1975 124 Spider 8 Relays?

Posted: Wed Jul 24, 2019 4:53 pm
by Grothmanr
I did this on my '75 Coupe.
I removed 128/4, 6, 7, & 8; points, diverter, diodes, & catalyst.
However, I converted to single points, which I recommend. The car starts so much better, cold or hot. I barely touch the key.
Why it had a catalyst relay IDNK. It never had a catalytic converter.

Re: 1975 124 Spider 8 Relays?

Posted: Wed Jul 24, 2019 7:14 pm
by friedman
Understand that my 75 project spider came with a 2L motor and electronic ignition. I like to keep my Fiat wiring as simple as possible.

There were 8 relays under the hood:
1. Ignition mode...don't need it since I have electronic ignition, if you have dual point distributor, get rid of one set and chuck the relay.
2. Fuel pump (factory electric fuel pump). I modified my circuit so the fuel pump comes on when the ignition is on so I didn't need this relay. You can leave it since the stock circuit uses a signal wire from the oil pressure light sending unit.
3. Charging light relay. My car came with the later alternator with the integral voltage regulator so I don't use this relay (or the metal voltage regulator on the fire wall near the relays).
4. Horn relay. I kept this.
5. Diverter valve by-pass relay...gone along with the diverter valve.
6. Diode relay....Have no clue what this is for so threw it away.
7. Fan relay. Fiat went back and forth on using relays for the radiator fan. For simplicity I threw it out.
8. Starter relay. Part of the seat belt interlock which everyone throws out so the relay went too.

Yup, looks like I only kept one relay. I also spent a week tracing all the wires going to these relays and pulling them out of the harness. I ended up with a LOT of wires on the garage floor.

Then both my X1/9s got totaled in a driveby accident and the spider went back outside the garage while a cobbled a third X.

I'm not advocating anything above that I did to anyone else, just a guide to be used or thrown away.

Also, my wiring diagram shows three boxes on the passenger side behind the dash, Buzzer (seatbelt I presume), buzzer relay and catalyst sensor. You can throw those away too.

Re: 1975 124 Spider 8 Relays?

Posted: Wed Jul 24, 2019 9:23 pm
by zonker
On my '71, I ditched the voltage regulator and alternator light relay, and added a starter relay and electric fuel pump relay. The alternator I am using the Denso style mini alternator (under $50 on ebay), mounted with a '76 up smog pump bracket on the top with the stock passenger side block mount on the bottom. With a relay on the electric fuel pump circuit, you can easily add a rollover switch to the 85 or 86 terminal wire to prevent the pump running in case of a rollover accident. The starter relay makes for a stronger voltage to engage the solenoid, and it also allows an underhood remote start switch (re-purposed the emissions idle bypass switch), which is real handy when you're replacing a timing belt or tuning up the motor.

Re: 1975 124 Spider 8 Relays?

Posted: Sun Jul 28, 2019 12:05 am
by kendall
Just so I know for sure, is this the best known complete wiring for the 1975 124 model?

I have a paper copy that is supposed to be correct from Bayless, but it looks to be correct for, I'm guessing, a 1974 model.

I might bite the bullet and break this down into a much cleaner version, if I find I hate myself enough.

There is a lot of wiring mickey mousing going on in that car, much more than just the radiator fan.

Re: 1975 124 Spider 8 Relays?

Posted: Sun Jul 28, 2019 8:53 am
by spider2081
I have found wire diagram are fairly accurate. I believe they are like building plans and the "as built" could be slightly different from the wire diagram. Also wire diagrams display the electrical connections and are not necessarily physically correct. I have found many Fiats with wire colors that do not match the wire diagram. I think during production if a color was not available the used what they had. Over the years changes we incorporated into the cars so a diagram could be correct for some of a model year but not all of the model year. I find it handy to have the previous and following years handy when working through a cars harnesses as you will be doing.
Fiat wire harnesses were fabricated in sections and blugged together as the car was assembled. Once the car is assembled these connectors serve no purpose but can cause intermittent issues. You might consider eliminating (splicing wires) some of the in line connectors in the dash area.

Hope this is some help

Re: 1975 124 Spider 8 Relays?

Posted: Sun Aug 11, 2019 9:37 pm
by kendall
zonker wrote:
Tue Jul 23, 2019 4:51 pm
As for converting to run when key is off, that can be done with the relay setup as well, it just means moving the current source to a battery only place. I mount a 5/16" insulated stud inside the passenger compartment and feed it with an 8 gauge wire from the large terminal on the alternator. I use this to run any add on equipment like electric fuel pump, stereos, subwoofer amplifiers, as well as a "brown wire mod" to help offload the old original wiring. The original wiring becomes the switched signals for the added relays such as the fuel pump, radiator fan, horn, headlights, etc. It cures 90 percent of the electrical gremlins that occurs on these little Italian gems.
zonker, I would be very interested to see how you did this stud. I didn't see much room under the dash to mount it, but I suppose on the wall it would be out of the way.

What components did you attach to your auxiliary stud? I'm thinking of attaching the radiator fan, headlights, fuel pump, and wiper motor to a separate source. Would that be too much? Did you add any relays?

Re: 1975 124 Spider 8 Relays?

Posted: Mon Aug 12, 2019 7:21 am
by rridge
In the library's general area are the Fiat NA service letters. In 1976 they issued a letter with the location of fuses and relays shown in diagrams of each model then sold for the model years 1974-1976. I think those diagrams are the most definitive ones available. ... /000-6.pdf