Which relay is which?

70spider · Post by **70spider** » Thu Mar 22, 2018 11:48 am

Well I was going to post a picture, however I guess I am to stupid to find a service where I can post pics for free. With that said my car is a 1970 and I am installing a 95 amp alternator so I will be eliminating the voltage regulator. I need to know which relay on the driver's side fender is which. Is the one nearest the firewall the Battery Charge Indicator? and is the one nearest the front the voltage regulator? I will continue to try to find out how to post pics. Thanks for any help.

Found a service here is the pic of my engine bay.

Yadkin · Post by **Yadkin** » Thu Mar 22, 2018 3:48 pm

Here's wiring diagram from an old Haynes manual that I have been using for my '74. I'm not sure what year its from and my car has additional factory circuits. I'll upload the item list in another post. 22 is the engine fan relay and has blue and violet wires. 23 is the battery charge indicator relay and it has a black wire.

Yadkin · Post by **Yadkin** » Thu Mar 22, 2018 3:50 pm

Item list:

zachmac · Post by **zachmac** » Sat Mar 24, 2018 8:50 am

Not trying to be a smart ass but it would be the one wired to the alternator. A simple continuity check between the alternator and the relay wires should tell you which one it is if you can't simply trace the wires.

70spider · Post by **70spider** » Sat Mar 24, 2018 9:24 am

A simple continuity check

That would be simple if one knew what a continuity check is. I was just trying to get an answer from someone who knows versus me taking a guess at it. I figure I will have to trust the wiring diagram and hope the previous owner (a mad electrical scientist) didn't mess with this system.

Yadkin · Post by **Yadkin** » Sat Mar 24, 2018 11:56 am

70spider wrote:
A simple continuity check
That would be simple if one knew what a continuity check is. I was just trying to get an answer from someone who knows versus me taking a guess at it. I figure I will have to trust the wiring diagram and hope the previous owner (a mad electrical scientist) didn't mess with this system.

Spend $20 and get yourself a volt-ohm meter. It's an essential tool. Try to get an analog type as those are better for a beginner (and they are less expensive). On the ohm setting, touch each end of a disconnected wire. If the ohms goes to zero then there is no resistance, meaning that the wire has continuity and will flow electricity.

zachmac · Post by **zachmac** » Mon Mar 26, 2018 5:36 am

Yadkin wrote:Spend $20 and get yourself a volt-ohm meter. It's an essential tool. Try to get an analog type as those are better for a beginner (and they are less expensive). On the ohm setting, touch each end of a disconnected wire. If the ohms goes to zero then there is no resistance, meaning that the wire has continuity and will flow electricity.

R = E/I Resistance = voltage divided by current. The multimeter has a battery of known voltage. When you place the two meter leads on either end of a circuit while selected to Ohms (the units of resistance) it causes a current flow that is inversely proportional to the resistance (the lower the resistance the greater the current for a set voltage). For a continuous wire (continuity meaning without break) the resistance is very low so the meter sees higher current (amps) for the set voltage applied. For a wire the resistance should read very low, only a few ohms at most. This reading tells you you have a complete circuit, i.e. that that wire is a continuous path between two points. If you disconnect the wire at the alternator you think is from the voltage regulator and disconnect the wire at the regulator and take a ohm reading between the two you should see only an ohm or two resistance thereby confirming that is the wire. If you see infinite resistance then the two connection points are not connected and that isn't the same wire.

BTW - none of this matters unless you are set on removing the voltage regulator from the fender. You will simply wire the new alternator per the instructions and leave the wires form the external regulator off.

spider2081 · Post by **spider2081** » Tue Mar 27, 2018 8:12 am

Try to get an analog type

For someone who has not used a volt/ohm meter I believe an analog meter is more easily damaged when accidentally connected reverse polarity or on the wrong scale. Digital meters usually display a + or - sign for polarity and are much more forgiving if used on the wrong scale. For the most part an inexpensive digital meter will be more robust and have more features than an similar priced analog meter. For a person learning to use a meter the digital meter Harbor Freight sometimes gives away "free" is a great meter to start with.

JohnMc · Post by **JohnMc** » Tue Mar 27, 2018 5:35 pm

In your photo "B" is the voltage regulator. "C" is the air horn relay (God I love air horns) and I cannot remember off hand what "A" is. Sorry for half an answer.

JohnMc · Post by **JohnMc** » Tue Mar 27, 2018 5:44 pm

You can download the 69-73 wiring diagram in .pdf. Since I am partially color blind my son has to help me with it.

https://sites.google.com/artigue.com/fiat/electrical

Which relay is which?

Which relay is which?

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