Windshield wiper wiring 1974 Spider

[Yadkin]

I'm redoing the entire electrical system as per Seneway's June 1, 2009 Revision C article. However it does not cover this issue.

The factory wiring diagram shows four devices for the windshield wipers. It does not show the variable resistor (intermittent delay). There is also a capacitor that was mounted under the dash and may be part of this circuit. The variable delay may be a late year addition that is not included in the diagram that I have.

This my best guess at this circuit, using the wire colors in the old harness. The wire colors with the boxed text, I can't figure out where they go. I've guessed at some. That's also my best guess for the capacitor.

Any electrical gurus out there that can help me figure this out?

Here's a link to the diagram below. You may have to copy and paste onto a new browser window.

https://photos.app.goo.gl/va2GzkcWnCattmvk7

[spider2081]

I am not a believer in rewiring cars. I believe in most cases its more practicable to repair problems.

I also am not the most knowledgeable person when it comes to Fiats
I believe early spiders were delivered with a wiper motor that had an electric winding for its field. These wiper motors used a variable resistor (rheostat to change the field current and the wipers speed. Later Spider windshield wiper motors were a permanent magnet motor with 2 internal windings for the 2 speeds. The permanent magnet motors used a 2 position switch to select which winding in the motor would be used or which speed the wipers would operate at.
I didn't know there was a period where both the 2 position speed switch and the rheostat was used.
I'm guessing a 1974 Spider would have been delivered with a permanent magnet wiper motor, If that is the case the rheostat would not be used and the white/black wire from the steering column wiper switch would be a ground to the switch.
Maybe the 74 is a transition year for the two motor types.

[18Fiatsandcounting]

I'll have to give this some more thought, but a few points:

- None of the spiders that I've seen had a variable delay. Variable speed, yes, and in the early models this was a rheostat between ground and a separate winding on the motor. Progressively grounding this winding slowed the motor. Later models had a two speed switch for slow and fast.

- There are really only 4 components: the wiper motor, the intermittent cycling relay, the speed rheostat/switch and the stalk switch on the steering column. I have never heard of a capacitor being part of this circuit, but someone may have added a time delay with an RC (resistor/capacitor) circuit.

- The wiper circuit is probably the most complicated of all the spider circuits, as it has intermittent, continuous, variable speed, and a self-park feature to return the wiper blades to their rest position no matter when you turn off the wipers (otherwise the blades would stop right when you turned off the wipers, such as in the middle of their travel). The windings of the motor are also grounded when you turn the switch off so that the wipers don't slowly grind to a halt. Very early models also triggered the wipers to do one sweep when you pumped the washer fluid pedal (yes, there was such a device on early models).

- By the way, the Fiat wipers are notorious for having only two speeds: slow, and even slower. Many upgrades have been done with more modern wiper motors, in particular VW wiper motors.

-Bryan

[Yadkin]

Thanks Bryan.

I made a change to the diagram, bench-wired this up:

https://drive.google.com/file/d/13G1JrJ ... sp=sharing

I did not connect Speed Switch 3 to Motor High because I have the motor assembly barely strapped down. I got the circuit to work mostly:

• Column switch position 0 and te motor parks itself.
  Position 1 and nothing.
  Position 2 I get low speed. Position 3 it stops (so the high most likely works.

My circuit has five components. The faces of the speed switch and rheostat are similar and have identical chrome bezels.

Why would there be an Interval Relay if there is no interval function.

[Yadkin]

For what it's worth I found some major issues with the original wiring. I have a lot of experience with Ford and Chevys, both known for safe, dependable electrical, and the stuff I saw on his car scared me.

• My old fuse panel is only ten fuses and was nearly melted together. Each of the fuses are ten amps so it requires four fuses for the headlamps.
  
  Additional in-line fuses that the factory had buried in the dash.
  
  Wires were unwrapped, and held to the chassis by sheet metal tabs. Years of vibration and a short would easily occur.
  
  No fuse between the alternator and battery. US cars of the era used fusible links to protect that circuit should the alternator short, dumping all the batter energy into large cable.
  
  The "charge fail" indicator is actually a 4-watt light bulb between switched power and then alternator. Should the bulb fail, the alternator won't change and you won't have any indication.

[18Fiatsandcounting]

I hear you. A few more thoughts:

- The fuses should each be 8 amps, except for one or two 16amp ones. If you have otherwise, someone has been in there before.

- Fiat used lots of connectors, so between those getting corroded and failing, and the poor grounds caused by corrosion, there's a lot of issues there.

- You are right: There is no fusible link as you would see on American cars.

- On the alternator charge light, you are correct in that the alternator on later model years would not charge if the bulb burned out, was missing, or was replaced with an LED lamp (not enough current flow). On earlier cars however, the charge light was activated by a relay and the alternator would continue to charge even if the light burned out. I don't know which one of these your '74 falls into. I *think* if it has an external voltage regulator over on the driver's side firewall, it is the earlier version. Alternators with internal voltage regulators would be the later versions.

- And just to make sure: The wiper stalk switch has 3 positions: Up is off, middle is intermittent cycling, and down is continuous. The wiper speed is that knob in the center of the dash. The intermittent cycling unit is way behind the gauge panel, and you have to remove that to get to the cycling unit.

-Bryan

[Yadkin]

You are right on the fuse sizes- it' been a while since I started this project and I got off it for far too long, and forgot many details.

Per Seneway's recommendation I have a modern 50 amp alternator which is self regulating. Three wires: charging, excitor, and ground. As has become my standard I use a thermally protected breaker between the charging cable and the battery, and use the alternator terminal as the connection point for the new fuse panel. Along with protecting against a catastrophe the breaker can be used as a switch to isolate the battery. This makes working on the car a bit easier.

I'm using the alternator charge light (on the tachometer) to indicate when the rear brake light is on. To monitor the alternator I've installed a simple digital voltmeter that also provides two USB charging points.

Back to the point of this discussion, the wiper circuit. The intermittent relay is a brass colored box Approximately 3" x 1" x 2" deep mounted behind the dash just under the windshield. It's labelled TEL 12C/2-12V-10A. There is another relay to the left of it which appears to be a standard relay (number on it is A72013) which appears to be for a different circuit.

So again, the 5th device, the dash-mounted rheostat, must be what controls the intermittent relay. I'm thinking that the capacitor builds up energy through the rheostat, but I don't understand the mechanism to release that energy to trigger the relay and let the motor run through one cycle.

[18Fiatsandcounting]

OK, fair enough. There are two relays behind the gauge panel, up against the firewall right below the windshield. The intermittent wiper relay, and the hazard lights flasher. The hazard flasher is a separate unit from the turn signal flasher, which is usually on the steering column support / pedal box, towards the center of the car. It can be reached from the footwell.

And yes, if you have a modern alternator with an internal regulator, then the alternator field winding won't be activated without current flow (usually through the charging light on the tach). No functional bulb or at least an equivalent circuit = no alternator charging.

-Bryan

[Yadkin]

I located a wiper diagram from 81-82 and adjusted my diagram accordingly. This makes more sense and I'll re-wire my bench test. It still lacks the potentiometer though.

https://drive.google.com/file/d/1BauaJd ... sp=sharing

[spider2081]

This makes more sense and I'll re-wire my bench test

Have you tested the wiper motor by it self.
the metal casting is ground.
Apply power to the gray wire (fast) then the light blue wire (slow)
This tests the motor.
I have tested a number of the motors at 14 volts they draw less than 4 amps with the gray wire powered. There i s no problem holding the motor with my hand during start up and run.
They draw less that 3 amps with the light blue wire powered.
I remove the short linkage from the motor arm so just the motor is operating. Pull the little clip and lift the linkage off the motors arm.
With the linkage disconnected from the motor the linkage should move very freely. If not it needs cleaning and lubrication

[Yadkin]

Yeah all that works, I was having trouble with the intermittent only, now solved using this diagram:
https://photos.google.com/photo/AF1QipP ... MqULQJEQdM

I am able to vary the delay between cycles from about one to two seconds. Not much of a variation.

The only issue is that when the interval switch is set to infinity the relay does a series of odd clicks.

I found no change by adding the capacitor to the circuit. That must be for something else, but I have no idea what it could be.

[spider2081]

I found no change by adding the capacitor to the circuit.

The capacitor may have been added by a previous owner. If a radio was installed it could have been used as a noise filter for the audio.
My understanding of the delay circuit is: The delay is a fixed time determined by an RC time constant circuit contained in the delay module. It sets the time between the wiper sweeps. The speed the wiper moves across the windshield is determined by the 2 position speed switch changing the speed selected by the speed switch does not effect the time between each sweep.

[Yadkin]

It could be for the radio, thanks.

[18Fiatsandcounting]

The only issue is that when the interval switch is set to infinity the relay does a series of odd clicks.

I don't know if this is the issue in your case, but when the cycling relay "stutters" (clicks), the issue is often dirty/pitted contacts for the thermal switch inside the unit. I've been able to take apart these units and clean/polish the points, which solved the problem.

-Bryan

[spider2081]

The only issue is that when the interval switch is set to infinity the relay does a series of odd clicks.

I can no longer get your diagram links to open.
The wire diagram I have for the 1982 wiper circuit shows the following:
steering column switch
Wiper delay timer
Wiper speed switch (2 position)
windshield wiper motor assembly/park switch

I don't know what you are calling the " interval switch"