Electrical Question #15 Need Help Please, I'm totally stumped this time Options

[76-914]

I'm going to have several electrical questions. 1st, Is pin #8, on the 14 pin plug at the relay board, the only switched 12v+ source in the engine compartment? TIA, Kent

[Mike Bellis]

I'm going to have several electrical questions. 1st, Is pin #8, on the 14 pin plug at the relay board, the only switched 12v+ source in the engine compartment? TIA, Kent

Yes, Can be used as a coil power wire when switching to carbs as well.

Black wire

[JeffBowlsby]

Careful, not all model years are the same. Check the schematic for your car.

[Tom]

I checked all of the schematics I can find and all have the black wires at pin #8 as switched hot from the key switch. To be safe, put a meter on it and verify that it is hot when switched on at the key switch. Battery isn't necessary to check that it would be hot. Just use one meter lead on the 4 red wires, the other on pin #8. With the key to on, you should have continuity. Key to off, open. What year car?
Tom

[76-914]

I checked all of the schematics I can find and all have the black wires at pin #8 as switched hot from the key switch. To be safe, put a meter on it and verify that it is hot when switched on at the key switch. Battery isn't necessary to check that it would be hot. Just use one meter lead on the 4 red wires, the other on pin #8. With the key to on, you should have continuity. Key to off, open. What year car?
Tom

It's my '73 Tom, which was a 1.7 originally with your fused adapter in place. My plan is to use this wire to activate a new power relay. Glad you and Mike are here to oversee this part.

[76-914]

Question #2 - Do I need to use a N/C relay off the starter circuit to kill the radiator fans when cranking/starting. I'm hoping the answer is no but thought I'd better ask now. TIA, Kent

[Tom]

Kent,
Don't know why as they don't draw that much. Is the Subie ECU controlling them? If so, that feature may already be in place inside the ECU because Subaru found it to be an issue, but I don't know for sure. If you found it to be a problem, it wouldn't be that hard to remedy. A 30 amp relay wired for the starter circuit to open the fan circuit. Basically the fan power to 30, ground to 85, fan energized to 87A (NC contact), and starter power from the key switch to 86. Whenever the starter circuit is energized, the relay opens and fans have no power. Stop starting, power to fans is back.
I think this would mostly depend on how much current the fans draw if the engine is hot and both are running to cool it. Say you drive 15 miles to the store and are inside 5 min and come back out. Would the fans still be running? This would also be determined on the battery condition and CCA. A battery with 500CCA will give 30 seconds of cranking at a big amperage without falling below a certain percentage of battery voltage. So if the starter is drawing 120 amps and fans 30 amps, that should not be a problem unless the battery is on the way out.
Tom

EDIT: Cold cranking amperes (CCA) is the amount of current a battery can provide at 0 °F (−18 °C). The rating is defined as the current a lead-acid battery at that temperature can deliver for 30 seconds and maintain at least 1.2 volts per cell (7.2 volts for a 12-volt battery). It is a more demanding test than those at higher temperatures. This is the most widely used cranking measurement for comparison purposes.

[76-914]

Damn, (IMG:style_emoticons/default/chair.gif) I didn't consider that the ECU would have that covered.

[76-914]

#3 - What is the difference between a 5AG 30A fuse vs. a AGU 30A fuse. Are they interchangeable? TIA, Kent

[Tom]

Kent,
The designations before the Amperage is for applications such as voltage, current flash over, and several other factors. Also designates glass enclosed or ceramic enclosed, what type of coating on the ends, etc. You would need to look each one up to determine which fuses these are meant for. This is why I stayed with ATC for my fuse blocks. It prevents someone from putting a clear glass fuse that "looks" the same in a circuit and the fuse is not rated at what the person thought. I don't know how many times I have worked on electronic equipment that some one replaced the fuse with one that looked identical until you read the inscription on the fuse that indicated it was for a 28 volt use and it was placed in a 125 volt circuit. Not good, as the fuse was no longer protecting the circuit as the proper fuse would. If you are interested in expanding your knowledge, look up "FUSEOLOGY". Very enlightening.
Tom

Edit: some research discovered. AG = auto glass
AGU = Fast-Acting Glass Tube Midget Fuses

[76-914]

Had to read thru some heavy stuff for my pea brain but I was able to learn this much. The 5 denotes it's physical size. In my case 13/32" x 1.5". That car fuses are slow blow to handle the large surges and are usually the 32V group. Now I need to take a nap. (IMG:style_emoticons/default/slits.gif)

[Dtjaden]

The easiest location for switched 12v on the relay board is pin 1 on the 4 pin spade lug connector on the relay board. The location on the board is toward the rear on the drivers side.

[76-914]

That could be useful info for someone that is using the relay board. I 86'd mine during the Suby conversion, however. (IMG:style_emoticons/default/biggrin.gif)

[76-914]

#4- I need to tie in my alt light with the suby engine. I have a single wire from the Suby to connect to the GEN light but don't know where to tie it in. I looked at Jeff B's info (thx Jeff) and found which bulb it is and there are 2 wires. A R/W and a G/R wire. The R/W goes to fuse 9 and to other gage bulbs so I can rule that one out. Maybe a switched + for bulb power? That leaves me with the G/R which goes to the relay board #5 on the 14 pin plug then out the 12 pin #1 to the OIL pressure switch. I don't understand this.

[Dave_Darling]

Green/red would be the oil pressure light, not the alternator light.

That one has a blue wire and a red/white wire. The red/white supplies +12V, while the blue wire connects to the D+ wire coming from the alternator to the voltage regulator.

--DD

[Mike Bellis]

The alternator lamp work with 2 positive leads. One is switched from the key, through a fuse and to the lamp. The other is the D+ from the alternator. When the alternator spins and creates voltage (2nd positive) the dash lamp turns off. When the engine is not running, the D+ turns "less positive" and the lamp lights up.

[Tom]

That red/white that goes to fuse #9 on the fused side is the correct wire for one side of the alt bulb. The other side is a blue wire that goes to the alternator at D+.
Tom

[76-914]

Odd. I have one sch showing GR yet today I find the one you mention w/ Blue on another print out in Jeff material. Are there two and I have the wrong one?? Many TY's for the assistance, guy's. (IMG:style_emoticons/default/WTF.gif)

[JeffBowlsby]

Odd. I have one sch showing GR yet today I find the one you mention w/ Blue on another print out in Jeff material. Are there two and I have the wrong one?? Many TY's for the assistance, guy's. (IMG:style_emoticons/default/WTF.gif)

That diagram was superseded., it was not correct. I try to keep the website materials correct, and I replaced that former diagram on the website in May 2013 with this corrected one. Keep in mind that this diagram is only for the 1974 model years, other years are different:

[76-914]

#5 - If you own a 914 you know the importance of a good ground. As I went through the Subaru harness I counted over 20 grounding points so Suby has a good idea, also.
My question is this. Are there rules that govern grounds? If so, can a layman understand them? Can a ground junction become ineffective if too many grounds converge at one point? Does a ground need to be sized? Should it be the same gauge as the positive circuit it completes? If adding ground points does the material type matter? e.g. brass, steel. As always, TIA, Kent