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Alternator relay/wiring help.

NateCrisman

Well-known member
Joined
Nov 22, 2008
Messages
2,054
Location
Blairstown, NJ
Ok guys, this is for #139/1000. I just put the car together and got it running, but the alternator is not charging. The alt has been relocated to the rear of the block with a Jay Racing kit, so the wiring has been redone.

The Alt came from my previous GVR4, which was working fine as of May when I took it apart to start rebuilding this shell. If the Alt went bad, it happened while sitting on a shelf. I did nothing more to it than shoot it with some carb cleaner to remove some oil grime before putting it on the engine prior to installation.

Alt has 3 wires:
large double white wire. goes from the Alt post to a 100amp fuse, then to the battery + terminal. I get the same battery voltage at every point along the + line from Alt post and both sides of the fuse terminals.

Yellow wire. fairly thick. It goes to a pink fuse link in the engine bay fuse box. I get battery voltage at both ends of this yellow wire (alt plug and inside the fuse box).

Small white wire. This is T'd into a white wire that runs from the front engine fuse box alternator relay, along the front chassis harness, then into the drivers footwell behind the interior fuse box. I have tested continuity on this wire to the pin of the alt relay, so the wire is good.

Im not 100% sure how the alternator relay inside the front fuse box works. When you unplug the relay, there are 3 male pins going into the fuse box, with a 4th that is cut short. But if you take the fuse box off the car, looking from the bottom there is only the small white wire (mentioned above that goes to the Alt plug) and a black/white larger wire. The 3rd pin has no wire. What does that little black box do? If it's bad will it cause the Alt to not charge? Is there any way to test that thing?

I really want to cover every base I can before having to pull the alternator and swap for another, it's going to be especially pita since it's now jammed behind the engine. As pita as changing an AC compressor.

Any help or suggestions appriciated.
 

iceman69510

Turn Right Racing
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Mar 5, 2001
Messages
10,964
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Michigan
I searched the electrical manual last night, but could only find two of the four relay terminals in the schematic (the triggered side, not the trigger side). That relay controls the 12V that lights off the alternator, so that could definitely be your source of the problem if the wiring is hacked.

I saw in your other post about the light, and that may be true the bulb is out unless that wiring is also messed with, as the light should come on with just the ignition on.
 

NateCrisman

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Joined
Nov 22, 2008
Messages
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Location
Blairstown, NJ
I checked this morning:
Bck/wht wire in fusebox going to the alt relay is ign switched +12v.
The other white wire to alt relay goes to the alt plug.
Jumpering the two wires, putting 12v to the alt white wire doesn't make it charge.

Guess the alt has to be bad.
 

toybreaker

iconoclast
Joined
Apr 30, 2006
Messages
3,581
Quote:
large double white wire. goes from the Alt post to a 100amp fuse, then to the battery + terminal. I get the same battery voltage at every point along the + line from Alt post and both sides of the fuse terminals.




Good to go.

Quote:
Yellow wire. fairly thick. It goes to a pink fuse link in the engine bay fuse box. I get battery voltage at both ends of this yellow wire (alt plug and inside the fuse box).



That wire goes to the voltage regulator internally. The voltage it applies is used to monitor the system voltage. The voltage regulator uses it to regulate the field coil voltage.

Quote:
Small white wire.



This is the field wire.

The voltage it applies goes to the field coil windings.

Quote:
This is T'd into a white wire that runs from the front engine fuse box alternator relay, along the front chassis harness, then into the drivers footwell behind the interior fuse box. I have tested continuity on this wire to the pin of the alt relay, so the wire is good.



This is a parrallel circuit consisting of the battery light in the dash and the alternator shunt relay, both feeding the "l" terminal at the alternator.

Voltage from the key in the run position (black/white wire) is fed to the circuit.

One leg goes to the battery light, and will illuminate it, (key on/engine off). This is because the alt isn't making any juice, so the field coil is at a low potential. After the engine starts, the field voltage increases, and without a difference in potential, the light goes out. If the battery light doesn't illuminate, check for power, key on, at fuse #9 (10amp

The other leg goes thru the alternator shunt relay, and, eventually ends up at the same place. The shunt relay is *generally* used to give an alternate power path to the "l" terminal if the battery light burns out.

I just looked up the diagram, after Dave said there was only two terminals shown. As we're all finding out, that's where it get's a little confusing.

The pictograph of that "relay" is interesting.

It "appears" to show a resistor and a diode, and no moving parts...

If you think about the how the circuit should work, no moving parts would be required for that surrogate signal to go out to the alternator, so why the relay?...

It might just be a device that inserts a resistance in the circuit, so the battery light doesn't get backfed or something, I dunno. /ubbthreads/images/graemlins/dunno.gif

At any rate, there should be power at the "l" and "s" terminals with the key on.

Is that the case?

Quote:
I did nothing more to it than shoot it with some carb cleaner to remove some oil grime before putting it on the engine prior to installation.



I almost hate to say it, but it's possible something got washed down inside. /ubbthreads/images/graemlins/frown.gif

Just putting a film of non conductive material on the commutator is enough to keep the brushes from tranferring juice.

Brake and electrical parts cleaner is a zero residue cleaner, and might be a better choice if you have to dissassemble it and clean it more thoroughly


[as an aside, many german cars don't have a shunt relay, and if the bulb burns out, well your battery and checkbook are about to be drained.
...Many a flat rate tech has been heard to mutter...
"I put a hundert and three damn alternmonators in this dayum vw, an it's still not charging, Floyd, get me annudder altermonator, maybe dis one'll work, tell Billy Bob we want the top shelf stuff this time, an if it doan work I'ma gonna hightail it over dere an I'ma gonna stomp a mudhole in his eye"...

During field trials, those wily mitsubishi engineers must have calculated the battery lite bulb service hours (on a logrythmic scale) versus the likely alternator flame 0ut time curve, and realised that not only was an alternative path around the battery lite bulb a good idea, it was a design imperative... Probably engineered a heat sink around the battery lite bulb base as well, to keep from melting the socket...]

But, I could be wrong /ubbthreads/images/graemlins/wink.gif
 

toybreaker

iconoclast
Joined
Apr 30, 2006
Messages
3,581
Quote:
Guess the alt has to be bad.



Before you pull it, try running a jumper ground to the case, and see if that helps.

You might be missing the other half of the circuit, the ground side. /ubbthreads/images/graemlins/dunno.gif
 

NateCrisman

Well-known member
Joined
Nov 22, 2008
Messages
2,054
Location
Blairstown, NJ
yeah that black box is weird. It's called an Alternator Relay, but it's not really a relay. It's got 3 pins sticking out the bottom, but only two wires going to it on the fuse box.
Schematic seems like you said, a resistor and a diode. Guess it doesn't matter, I have power at both wires on the alternator plug and a full path from the Alt post to the battery, and still get nothing for charge.

The only thing to try is maybe adding a ground strap between the alt body and the - batt terminal? (I'd put my chances of that working about the same as seeing Frank Zappa at my dinner table tonight)

Tonight is going to suck: The Xcase has to come out to give me room to get my arm in to remove the JMF coil bracket from the bottom. Then take off the intake manifold, fuel rail and getting all that top end stuff tangled up to get the alt out the top.
 

iceman69510

Turn Right Racing
Staff member
Joined
Mar 5, 2001
Messages
10,964
Location
Michigan
Quoting toybreaker:
Quote:
Guess the alt has to be bad.



Before you pull it, try running a jumper ground to the case, and see if that helps.

You might be missing the other half of the circuit, the ground side. /ubbthreads/images/graemlins/dunno.gif



I second that one. Thought of it later.
 

NateCrisman

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Joined
Nov 22, 2008
Messages
2,054
Location
Blairstown, NJ
No luck on the ground strap; still 12.2 volts or less.

I pulled the downpipe, jmf coil bracket, and intake manifold this afternoon. Taking this alt and a spare to napa in the morning to bench test both.
 

NateCrisman

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Joined
Nov 22, 2008
Messages
2,054
Location
Blairstown, NJ
I took 3 alternators (the one removed from my car suspected bad, as well as two spares that came out of parts cars) to NAPA this morning to use their bench tester.

I walked out with 3 alternators making 14.7 to 15.3V on the machine. So there must be something I'm overlooking? /ubbthreads/images/graemlins/bawling.gif
 

gtluke

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Joined
Sep 16, 2001
Messages
4,210
Location
dirty jersey
wow wtf?

my alternators have always charged with BOTH the signal wires broken. It's happened twice to me so far /ubbthreads/images/graemlins/smile.gif
You can tell when they break because the voltage is all over the place, from 12.8 to like 15.5!

Make sure the alternator output wire actually makes it all the way to the battery? and that the battery is actually hooked up to everything? Where are you reading this voltage? on the logger?
 

NateCrisman

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Joined
Nov 22, 2008
Messages
2,054
Location
Blairstown, NJ
Using my fluke voltmeter. I'm not sure how an ASE certified tech with an automotive engineering degree can't figure out a stupid non-functioning alternator. sad /ubbthreads/images/graemlins/banghead.gif

Im going to put the same alt back in this afternoon, add a couple more ground straps just for good measure and just go over every connection again to be 100% sure. /ubbthreads/images/graemlins/dunno.gif
 

NateCrisman

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Joined
Nov 22, 2008
Messages
2,054
Location
Blairstown, NJ
I figured out the problem today after going over the whole system more than 3 times, and it ended up being a lucky hit that I found the problem:

There is an orange silicone rubber grommet/seal on the 2 wire plug that goes into the alternator. Ended up there was an orange seal on the plug and also an orange plug stuck inside the alternator, so the plug wasn't able to engage far enough to make electrical contact on the spade connectors. Simple and dumb. /ubbthreads/images/graemlins/bawling.gif
 

Nice!

I like easy. /ubbthreads/images/graemlins/smile.gif

So the problem was one too many connector sealing gaskets?

I've done that with an oil filter. It made a mess, and then some!
 
Last edited by a moderator:

NateCrisman

Well-known member
Joined
Nov 22, 2008
Messages
2,054
Location
Blairstown, NJ
Yes, the alternator came out my previous running VR4 with the seal stuck in it. I bought a better gvr4 shell and swapped everything into the new body. I used the wiring harnesses from the new shell, of which the alternator plug on the harness also had the seal on it.
 
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