Restoration of Pearl 94 LSI - Electrical issues
 

So I'm restoring a 94 Pearl LSI. I'm halfway finished and some dash lights are throwing me a curve. I've read almost every post here regarding lights on the dash (including Trevors posts), but I still need some help. Here's the issue...

When the car is running, the Charging (Battery), Brake, and Stop Lamb dash lights are illuminated. I have swapped in 2 different alternators from 2 other SVX's and the lights are still on.

I have unplugged the Alternator plug, while running and the lights go out...hurray! So its an alternator issue, right? Hang on, If I use that same alternator in my daily driver SVX, the dash lights do not illuminate and I read ~14.5 volts charging at the battery. The same alternator produces ~15.5 volts at the battery on the SVX with the dash lights on.

I have tried a new battery, but not a new battery with a swapped in Alternator....hmm..I wonder if I have a bad battery too? O.K. next step is to test the battery's load response and/or swap the battery that I know is good from daily driver into the 94.

Regardless, I would appreciate any input from those that have resolved a similar issue or any EE's, or really anyone for that matter, that wants to weigh in. Just looking to repair the issue so I can move on the remainder of restoration, repainting black top and trunk lid, replacing rusted sunroof drip tray, rear diff thumbing issue, oil leaks from valve covers, non functional AC, etc.

Here are some other electrical issues I've noted.

• Battery to body ground repaired. Was rusted badly and I replaced the ground wire with a heavy gauge wire and ran it to the tie down hook bolt on the frame rail.
• Rack & Pinion was replaced at some time prior to my ownership, with a non-speed sensitive unit. The wire harness connector for the rack is unplugged, obviously...nothing to plug it into.
• One of the Transmission wire harness plugs was damaged while swapping in a good transmission. The plastic surround was broken but the mail wire connectors were undamaged. This plug is held together with electrical tape, until I find time to repair it correctly. The car shifts fine, no issues with the transmission.

Re: Restoration of Pearl 94 LSI - Electrical issues
 

sounds like it could be an ignition switch (electrical part) issue. try moving your key around in the cylinder when it happens and see if anything changes, or jump power from the battery directly to a fuse with power only when the key is on, if the lights go out then something is not getting good contact in the switch.

Re: Restoration of Pearl 94 LSI - Electrical issues
 

"15.5 volts at the battery on the SVX with the dash lights on". This says that there is trouble with the alternator sensing the battery voltage,. that is too high at 15.5V.
There is a separate wire that tells the alt what the battery voltage is. I would think this wire is open. it runs from the Ignition switch to the plug on the side of the alt.

Read this bit on the alt from the WSM.
http://www.subaru-svx.net/photos/files/oab_au/4101.jpg

Harvey.

Re: Restoration of Pearl 94 LSI - Electrical issues
 

After looking over the electrical service manual, as well as having discussions with Maniac Electric Motors and an accredited electrical engineer, here are my thoughts on this.


15.5V can be accepted as within normal commercial tolerances, as the electrical manual allows 16V. There should be no reason why 15.5V DC should cause the trouble lights in question to illuminate.

The pilot voltage sensing wire referred to connects directly at the distribution box and is shown as "S" (sensing circuit) in the wiring diagram. It does not physically run to the ignition switch. The diagram is a only a schematic, and in any event this circuit should not cause the problem.

The fault most likely involves the circuit marked "L", (the alternator fault indication circuit), which is closed if the alternator is not charging.

This circuit normally illuminates the steering, stop check, brake and charging lights when connected to ground, via a transistor. But in this instance the steering light is not illuminated because the steering has been altered, as stated in the original post..

This wiring running between the alternator and dash and its connections should be checked for a short circuit, rather than an open circuit.I would pay particular attention to the area around the alternator, where damage is most likely to occur.


If this is the case, the alternator is working as designed in your daily driver, but not the other SVX. The only thing that changes is the wiring and electrical circuitry between the two cars.

Simple logic tells me this:

2 different cars.
Alternator works correctly in car 1
Alternator works incorrectly in car 2
Only thing common between the cars is the wiring.

Therefore, problem exists in the wiring of car 2.

I a not sure how much of a role the disconnected steering rack plug plays in all of this though. This is the only other difference.


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Re: Restoration of Pearl 94 LSI - Electrical issues
 

I think you guys are right on. I discussed this with my friend (Nissan master tech) last night and after going through the electrical diagrams he concurs that this is a short or bad connection (voltage drop) between the alt and the dash. ;)

Thanks for the input. I'll let you guys know what I find and what the issue is once resolved.

Re: Restoration of Pearl 94 LSI - Electrical issues
 

John I don't have to guess who, the wording says it all.:)

15.5 volts is not accepted as normal. No lead acid battery likes to be charged above 14.8 volts. The 16 volts that your accredited electrical engineer has read in the manual, is referring to the the failsafe 16 volt zener diode that is connected in the regulator circuit to prevent the voltage rising above 16 volts, to protect the cars electrical components, in the event that it no longer can read the battery voltage.

It is the black/red wire in the plug on the side of the alt that reads the battery voltage. If the ignition is on there should be battery voltage on the wire.

Harvey.

Re: Restoration of Pearl 94 LSI - Electrical issues
 

Harvey, sorry but you do have to guess who my electrical engineer friend is and he was trying to understand the actual reason for your post. :) :lol:

He and I read the page of the manual you posted. You are correct in saying that 15.5 volts is not accepted as normal, provided that the a normal battery is normally connected for normal charging.

But as the manual shows the voltage can rise to 16 volts without there being an actual alternator fault, as this is the upper limit set by the regulator.

By the way my friend points out that there is not a secondary fail-safe Zener diode within the regulator as you have described.

As you said, there should be battery voltage on the wire, but what has all this to do with svxcuseme's problem and how can 15.5V-16V cause the indicator lights to come on as you said in your post? What is wrong
with the advice that I have posted?


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Re: Restoration of Pearl 94 LSI - Electrical issues
 

Thank you John for the relay.:D I don't think your friend has a clue what he is talking about.

I don't think for a minuet that this battery, is not connected to a normal alternator in a normal car.:)

The manual shows that 16 volts is upper limit set by the zener diode, to protect the cars systems, in the event of the black/red sense wire, becoming open circuit. This is why it has set the warning lights. The upper limit set by this reg, and all automotive 12 volt regulators is 14.8 volts.

This may be news to your friend, but in electronics, a zener diode is universally used to set voltage levels.

This is the wire that the regulator uses to see what the battery voltage is, to control the system voltage. If this wire is not connected to the battery voltage, the regulator falls back on the Zeners diode's set limit of 16 volts and sets the warning lights. 16 volts is the maximum voltage allowed by the electronic components used in the cars controllers.
This is the connection, I believe is related to Svxcueseme's problem.:)

Harvey.

Re: Restoration of Pearl 94 LSI - Electrical issues
 

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My friend has more than a good understanding regarding Zener diodes. What he clearly said was, "there is not a secondary fail-safe Zener diode within the regulator as you have described."

He believes the Zener diode you are referring to is included within an integrated circuit. This will not be a 16V Zener diode as it will be setting a voltage applied to a transistor, along with other electronic items which control the charging current.

Harvey, there is certainly no reason for an argument. Two possibilities have been posted, Your responses come across to him as an absolute statement, while I have simply offered my thoughts. In order to dominate the thread, you are opposition to what we seem to be saying, but have not been able to show that those observations are wrong.

My friend has continued to be interested in the thread, mainly because of the rather arrogant, disparaging remarks made against him and his qualifications.

There is a third possibility which, although unlikely, should be considered if checks have so far not found the problem.

Apparently the power steering connections have been left entirely disconnected. However, if for some strange reason, voltage is being connected to the power steering fault sensing wire

This could upset the voltage regulator, as this would then receive positive voltage on its fault light switching circuitry. This is because it is connected through a diode so as to bring on the steering light as a test when the ignition is first turned on. This could upset the regulator and be a possible reason for both the incorrect lighting of the fault lights. as well as the above average voltage output.

This is something to check, since the differences between the two SVXs also the steering rack connection (or lack of). Maybe hook the alternator back up to the "daily driver" SVX (where it worked correctly) and unplug the steering rack connections to see what happens. This could eliminate that as a possibility.

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Re: Restoration of Pearl 94 LSI - Electrical issues
 

Sorry John, your friend has tried for 7 years to involve me in his pointless arguments. I see no reason to continue, I have said my piece.:)

Harvey.

Re: Restoration of Pearl 94 LSI - Electrical issues
 

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Harvey,

Leaving all the recent electrical diagnosis out of this, I want to return to the very first post by svxcuseme

He said that using that the alternator in his daily-driver SVX, the dash lights do not illuminate and has a reading of ~14.5V at the battery, which indicates a properly-functioning alternator.

However, this same alternator produces ~15.5V at the battery on the 94 SVX and the dash lights on.

The only two differences between these two cars are the actual external wiring itself and the unplugged electrical connection at the steering rack on the 94, because it was the incorrect part

As I stated earlier, it is easy to eliminate one of these possibilities by installing the alternator back on the daily driver and unplugging the steering rack connection to try and duplicate the symptoms. If all is well, that only leaves the wiring to be suspect.

I believe there is now enough information posted to provide a complete picture.

I have said my piece as well. :)

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