1G 1g alternator Voltage sensing wire?

[forcefed86]

Which wire in the plug is the voltage sensing wire?

Finally found a downloadable manual... A ton of mis information about what these 2 wires are on this sight... Here is is plain as day.

 

[spydur8385]

The one labeled b terminal is where you get +12v...

 

[steve]

Here's what the 91 FSM says. Sometimes Japanese to English gives interesting sentences, I think they are saying that the voltage regulator sense terminal is "S".


OPERATION
When engine is stopped

When the ignition switch is switched to the "ON" position, electricity flows from the "L" terminal, of the alternator to the field coil, and at the same time the charging warning light illuminates.
NOTE
The alternator relay functions as a back-up for the flow of electricity to the field coil if there is a disconnection or damaged wiring of the charging warning light.

When engine is being started/has started

When the engine is started, charging voltage is applied to the "L" terminal of the alternator, with the result that the charging warning light is extinguished.
In addition, because battery voltage is applied to the "S" terminal of the alternator, this battery voltage is monitored at the IC voltage regulator, thus switching ON and OFF the current to the field coil and thereby controlling the amount of generation by the alternator.
Power is supplied to each load from the "B" terminal of the alternator.

 

[forcefed86]

Gotcha thats pretty much how all the 3 wire alternators work and are wired. Field wire turns the alternator "on" and the "S" controls voltage output. I got that part. I was just needing to know which wire was the S term.

I was thinking that the smaller gauge wire was the sense wire "S" term. And the larger wire went to the "L" term to excite the coils. This is not the case according the 90 factory manual. It shows the the larger yellow wire being the sense wire.

On my other car I'm using a CS series GM alternator. Using a SPDT pressure switch and a 5v ref. I can temp. raise the voltage output of the alternator while under boost. I have it set around 20psi to give my fuel pump an extra boost under.... boost.

The TT supra pumps are voltage hungry and output is raised significantly from 13v to 14-15v+.

My Rx-7 jumps to 15.2 volts at wot. I was hoping to do similar with the DSM alternator on my 1g.

This isn't necessary for most but I'm running e85 and 1 pump. This is alot cheaper than additional pumps and has worked well for me in the past.

I'll make a post in the tech section if it works.

Pretty much the same thing as the caspers voltage booster.

Thanks!

 

[steve]

The later FSM says the sense is the Yellow wire to pin 1 of the alternator connector and runs to subfusible link 4.

 

[forcefed86]

The later FSM says the sense is the Black/Yellow wire to pin 1 of the alternator connector and runs to subfusible link 4.

So shouldn't the S term have power even with the IGN off? Since the 90 FSM is showing a picture of the actual alternator, that would mean that mitsu changed there terminals around on the alternator? That seems odd... think you could take a snap shot of that for me?

 

[steve]

So shouldn't the S term have power even with the IGN off? Since the 90 FSM is showing a picture of the actual alternator, that would mean that mitsu changed there terminals around on the alternator? That seems odd... think you could take a snap shot of that for me?

I double checked the 90, 91, and 92-94 Eclipse electrical hardcopy FSMs this morning and I misread the PDF last night. You're correct that it's a 2mm Yellow wire. I read the F (for flexable) as a badly scanned B in the PDF version. All the manuals agree that the S terminal is pin 1 of the connector and the L terminal is pin 2.

The way the diagrams show, yes the S terminal should have power all the time since there is only the 30A subfusible link and the Alternator fuse between it and the battery. #4 on 90 and 91's also powers the headlight pop-up motors.

The only place I found the image you posted was in the 90 DSM Technical Manual where the actual wiring diagrams are in the Electrical FSM under Charging System and Power Distribution. The PDF I was looking at last night is the same one as you can download. http://www.dsmtuners.com/forums/fre...tions/344490-download-1g-service-manuals.html

 

[forcefed86]

I double checked the 90, 91, and 92-94 Eclipse electrical hardcopy FSMs this morning and I misread the PDF last night. You're correct that it's a 2mm Yellow wire. I read the F (for flexable) as a badly scanned B in the PDF version. All the manuals agree that the S terminal is pin 1 of the connector and the L terminal is pin 2.

The way the diagrams show, yes the S terminal should have power all the time since there is only the 30A subfusible link and the Alternator fuse between it and the battery. #4 on 90 and 91's also powers the headlight pop-up motors.

The only place I found the image you posted was in the 90 DSM Technical Manual where the actual wiring diagrams are in the Electrical FSM under Charging System and Power Distribution. The PDF I was looking at last night is the same one as you can download. http://www.dsmtuners.com/forums/fre...tions/344490-download-1g-service-manuals.html

Thanks. New 90a alternator arrives today. The Car is a 93 so I don't think I'm powering any thing else in the circuit. I'll leave the wiring factory for now. And do a few more WOT pulls to see if voltage drops to 12.5 again.

Any ideas why jumping a 12V source (+bat term.) to the field coil would take out the alternator? I'm still puzzled by this and don't want the hassle of frying another alternator.

 

[steve]

Any ideas why jumping a 12V source (+bat term.) to the field coil would take out the alternator? I'm still puzzled by this and don't want the hassle of frying another alternator.

No, I understand how the alternator works in general but not specifics that might cause something like this. Both circuits that provide energizing voltage to the L terminal on startup have current limiting resistors but I don't know if that's a requirement or just for safety in case of a short.

 

[forcefed86]

No, I understand how the alternator works in general but not specifics that might cause something like this. Both circuits that provide energizing voltage to the L terminal on startup have current limiting resistors but I don't know if that's a requirement or just for safety in case of a short.

So Where is that 30A fusible link located? Installed the new alternator and I get a battery idiot light and no charge. Must have blown the fusible like I'm guessing? I pulled the cover off the alternator relay on the pass side engine compartment fuse area. Also the only alternator fuse I see is the large 80A deal? in the same pass side compartment? Is there another one I don't know about?

Thanks

Well I finished up my voltage booster circuit. Used a Devils Own SPDT pressure switch. Wired the NC term of the switch to the factory S wire and ran a 9v source to the NO term. Checked sense voltage at plug. 12.2V. Applied pressure to switch and term reads 9v.

***update***

I was thinking of an old school fusible link inline with wiring, hidden in the harness somewhere. Now I see they are just referring to the large block fuses on the passenger side engine compartment. Not sure what else to check. Pretty sure I'm down to the alternator "relay".

I got it.

It's the alternator "relay" although I've never seen a relay look like this!

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Looks like a diode and a resistor to me.

Anyway I jumped the relay and it started up and hummed at 14.2. Then applied shop pressure to the switch setup I made and it jumps to 15.2. Take away pressure and its back at 14.2.

Problem is now that I have removed the diode from "relay" by jumping it the car will stay running with the key in the off position. Pull the "relay" and it shuts off as it should.

So that is my problem, I fried the diode. Now I can't find another one of the relays except through a dealer. What a pain. If I knew the specs I'd just go get another diode and solder it in there. Anyone want to take a stab at it? I'm sure it's nothing special....

 

[steve]

Just use a big 400X series diode. As you discovered it's there to keep the alternator from back feeding into the ignition switch. You'll note that there is also one in the warning light path.

The diode just have to stand up to the reverse voltage from the L terminal so a diode with a couple hundred volt PIV should be fine.

 

[forcefed86]

Just use a big 400X series diode. As you discovered it's there to keep the alternator from back feeding into the ignition switch. You'll note that there is also one in the warning light path.

The diode just have to stand up to the reverse voltage from the L terminal so a diode with a couple hundred volt PIV should be fine.

So after a weekend in FLA I'm back home now and got a chance to work on this some more. Bought a simple diode at radio shack. And it fixed my run-on issues. Key shuts off the car as it should now. But I have another issue. Not sure if the alternator relay resistor is to blame here or not. I'm guessing it is. With the car shut off I can hear the ISC motor clicking away. If I pop out the alt relay it's dead quiet. Reinstall it and it starts clicking again. Also the resistor on the alt. relay is quite warm.

I'm guessing I fried the resistor when I fried the diode? I'm not really sure of the purpose of the resistor? Does anyone know.

Here are a few pics. I didn't have a "solder sucker" so I used compressed air to blow out the old solder. It's a bit messy, but it worked.

Original pic of alt. relay

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replacement diode

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New diode installed. I have since swapped in a 200v 1a diode thinking it may help with the ISC motor issue. It did not.

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Boost switch setup...

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Small vid of voltage boost...

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[steve]

First, wrong diode.
Second, you installed it backward.
Third, think about why the resistor gets hot.

Go google ohms law and look at how to calculate power. Those watts have to go somewhere and in a resistor they turn into heat.

 

[forcefed86]

First, wrong diode. Second you installed it backward. Third think about why the resistor gets hot.

Go google ohms law and look at how to calculate power. Those watts have to go somewhere and in a resistor they turn into heat.

First off thanks, I obviously had some things incorrect.

Like I said I changed out the diode... to a 1a 200v.

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How did I install it back wards? The black stripe faces up on the original diode and on my installation? Is the black stripe not the indication of direction of flow.

I understand why it gets warm. I was pointing out it was getting warm still drawing current when it should not. And was wondering if the resistor had anything to do with the ISC circuit.

 

[steve]

How did I install it back wards? The black stripe faces up on the original diode and on my installation? Is the black stripe not the indication of direction of flow.

It's the band that marks the Cathode but is the diode body is black the band is another color line silver or white. When the body is clear a black band is common.

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With the diode body that short I guess I'm confused by the markings and would have to look at the terminals and the schematic.

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It says that the diode anode is connected to the resistor and the cathode is connected to pin 2.

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Assuming that the wire wrapped across the two right terminals was something you did, I would guess that the rear most terminal is pin 4 and the closer one pin 2.

I can just make out that the left terminal is connected to the resistor and the diode (most of the wire is hiding behind the diode). Again, the schematic says the diode anode is connected to the resistor so the marking in question here is the silver one saying that end is the cathode.

The black band on your zener diode marks it's cathode so I'd say it was installed backward. Do you agree?

 

[forcefed86]

It's the band that marks the Cathode but is the diode body is black the band is another color line silver or white. When the body is clear a black band is common.


The black band on your zener diode marks it's cathode so I'd say it was installed backward. Do you agree?

Yes, the wire was what I used originally to jump the 2 terms.

Assuming the original diode uses the grey band and not a black to determine the cathode then yes I see your point and yes it was backwards. It's hard to see but the black band also has a grey circle in it. I thought this was designating the cathode.

I should be able to use the meter to test this. I will verify when I get home. I also seem to recall the radio shack diodes having a diagram on the back of the package. I'm 99% sure I have the grey band pointing up, which would be incorrect.

I'm sure it's something simple. Unfortunatly I have 30 mins a day if I'm lucky to "play" with my cars. So things get rushed and simple mistakes get made.

*********UPDATE**************

Installing the diode the correct direction fixes the issues with the ISC. I believe all is good now.


Thanks!

 

[steve]

Great. My guess is that by backfeeding the ignition switch you were keeping the ECU turned on.

 

[forcefed86]

UPDATE:

All is well, I'm at over 15v WOT. Roughly 2k miles on the car since. Voltage readings taken from my logger. Voltage is usually a half volt or more at battery. Hoping this gives my TTsupra pump a kick in the pants. Using all factory fuel lines/returns. (aftermarket regulator though).

 

[bling5tatus]

Sorry to zombie bump but I was wondering if you did anything to compensate in the tune for the extra fuel you would get manually turning the switch to on.

 

[steve]

Sorry to zombie bump but I was wondering if you did anything to compensate in the tune for the extra fuel you would get manually turning the switch to on.

Assuming a functional fuel pressure regulator, wouldn't he be getting the correct fueling rather than it leaning out as the pressure dropped due to the pump not keeping up?

 

[bling5tatus]

Ah that makes sense. It's not preventing a flow drop, it's preventing a pressure drop. The line is too small for flow to ever drop significantly? In other words the extra voltage at the pump isn't causing more fuel to go into the motor than normally would because it's regulated by the FPR... it just prevents a pressure drop.

Maybe I overread the part where the OP measured pressure drop in the logs.

 

[steve]

I know you know this...

Restricted flow creates pressure.

The FPR moderates the output flow to regulate the pressure. If the injectors allow more to escape than the pump can provide the pressure drops.

 

[Brando_DSM]

I found this old instruction sheet from a galant 90a alternator I had purchased some time ago. This just further solidifies the information.

 

[GRNDSM]

This is an awesome thread! I am trying to combine DSM/Mitsubishi alternator logic to my 1980 Triumph TR7 wiring, which actually looks VERY similar! TR7 also uses 3 wire alternator, with S line going back to the battery, WITHOUT a fuse in the system! I think I am going add 30AMP fuse to it.

I am keeping my fingers crossed that TR7's will put out a proper voltage for "L" line! I will have to measure it before I start the car for the first time!

 

[luv2rallye]

The alt Sense line is just that - it only senses (tests) the voltage at the battery (so the alt knows if it should put out more/less). It does not charge the battery through it so no fuse is needed (no current flows). If you really insist on having a fuse there just a 1A will do.