No charge to over charge

[Bob_D]

HELP! I suspect I have a bad voltage regulator, but have no good baseline to look at. Here's the problem: I got my 240Z (build date 9/73) over a year ago, and it was pretty obvious out of the box that the charging system was not working (Amp gauge shows discharge with lights and blinkers, but never goes to the + side). Since this has been a "plaything" for weekends I've been getting by with a trickle charger during the week to keep my battery topped off, and kept to daytime around-town driving on the weekends. I recently got a 60Amp alternator from Rock Auto (it came with a sticker claiming it was EXTERNALY REGULATED), and I purchased a new VR from NAPA. I put these items into my car and the AMP gauge will almost peg on the positive side when the RPM's are above 2500. Even at idle it is slightly to the + side. The old VR was a solid state unit but my new one is a traditional mechanical style. My confusion comes when looking at the wiring of the two voltage regulators, as the colors of the wires are not all in the same spot on the connector. Also, the wiring harness in the car only has 5 wires going to the rectangular 6 wire plug, but both voltage regulators have 6 conductors going to the plug.

 

See the attached sketch to understand why I am confused. The new VR wiring colors do not match the old one, and neither seems to match the wiring harness in the car. All these sketches are from the viewpoint of looking into the connector. When connected the solid black wires do match up with each other. On the wiring harness sketch I noted some wire colors in parenthasis, this is because I can't quite tell if the original color was white or yellow. I put my best guess down first, with an alternate color in parens, like this: White (Yellow?). Also, when two colors are noted, the second color is the stripe color, so White/Red means a white wire with a red stripe. I know that the original "from the factory" voltage regulator was of the mechnical type, and this solid state regulator was an aftermarket part. Is my new voltage regulator mis-wired?

EDIT: Putting in the older solid state VR resulted in a no charge condition with the new alternator.

Edited January 1, 2014 by Bob_D

[NewZed]

The high "+" on the ammeter typically means that a lot of amps are flowing.  Maybe because you're charging a discharged battery.  The missing wire is the "L" wire.  In theory, I think, the alternator should either not produce a charge or take an engine rev before it does.  "L" flows current through the windings to start the charging cycle.  Some alternators have enough residual magnetism to get things started.  It might work but it's not quite right.  In short though, you might not really have the problem that you think you have.

 

The great thing about the early Z's is that Nissan wrote extensive diagnostic procedures and diagrams in to the service manuals.

[Bob_D]

Hi NewZed, thanks for responding. My chassis harness looks original and unmolested where the voltage regulator plugs in, and according to the FSM (page BE-2, item 7), 5 wires to the connector are correct (no connection at "L"). I had considered that perhaps the battery was severely undercharged and was getting tons of current to help make up for that, but it was getting so much charge that electrolyte was leaking out from the inspection caps! Also, the battery is only a year old, and like I said in my first post I do keep it on a float charger during the week, and after 15 minutes of driving it around the Amp gauge still reads almost to the full + side and shows no sign of coming down. Being suspicious that perhaps my "budget" float charger wasn't actually keeping my battery topped off, I hooked up the battery to a regular charger. It showed that my battery has a full charge. So I am really suspicious of my new voltage regulator being mis-wired. Since I don't have an original equipment VR to compare against I don't have a way to confirm my suspicions, and my chief clue is because the new VR wiring does not match what is in the FSM (page EE-24), which details wire colors and locations that differ from my new VR. I am reluctant to just re-wire my new VR connector without getting some confirmation from a fellow Z owner that mine is incorrect. (My #1 suspicion is the white wire with red stripe being in the wrong position on the connector of the VR.) I am attaching a sketch of the backside of my new VR, can you confirm if it looks like yours? Thanks!

[thebruce]

It sounds like the alternator field is not being regulated at all, but getting full battery voltage all the time. If your new regulator has a part number you might be able to find a wiring diagram for it online.

I would personally ditch the mechanical one for solid state in a heartbeat, but I'm a little biased.

Don't run the car until this is fixed or you will be buying a new battery, might already be too late.

I'll run down to the shop in a minute and check what my reg looks like compared to your sketch.

[NewZed]

I have a 76 and my external VR is gone.  In retrospect, I recall other threads about five wires where there should be six so your harness might be right.  It would still be worthwhile running the diagnostics in the FSM.  See if the NAPA VR has the letter labels L, A, N, IG, F, E on the back and compare it to what should be.  Maybe you can swap a wire.

 

In the meantime you might re-title your thread to something like "1973 240Z has only 5 wires at the VR plug instead of 6" or something like that.  There are billions of "HELP, not charging right" threads out there.  Maybe even trillions.

[zster]

I suggest checking voltage with a meter.

[thebruce]

I have an early 74 260z. The plug is different, and all 6 wires are present. Harness is in really good shape, as in untouched. Worked right last it was run. May be apples and oranges here but I'll post the images anyway in case they help. Good luck!

[Bob_D]

Well I've managed to make things worse. Now none of my gauges are functioning. I found the upper left fuse was blown (marked Air ConD, 20Amp, but I don't have air conditioning) I replaced that, still no gauges. I noticed that the light behind the vent controls comes on when I turn the key on. I've never seen this before (or at least never noticed it before), and this is with the headlights off. I've checked continuity from the alternator to the VR plug, and all those wires show good continuity. The battery is reading 12.58 volts with the engine off or running with the old solid state VR.

 

NewZed: My Napa VR does not have any markings where the wires are solderd to their respective locations. That sure would have made it easy.

 

TheBruce: Thank you for getting me the picture and diagram, I appreciate the effort. Your VR looks very different from mine, so I am thinking like you, "apples and oranges".

 

It's getting too dark out in the garage for me to work any further today, but I really appreciate the suggestions you guys have given me. Please keep them coming! (Especially if you have any ideas why my gaiges quit working and how can I fix that!)

[Bob_D]

Last night I took the cover off the new VR and drew out the schematic using my DMM to confirm continuity. I have come to the conclusion that Napa must have sold me an incorrect VR (the box was right, but the contents, not so). I have attached my schematic, along with what the FSM shows on page EE-12, and as you can see, they don't come anywhere close to matching up. One obvious thing is that the FSM shows 3 resistors, the Napa part has 2, but even more concerning to me is that the E connector (black wire) connects to all sorts of things in the Napa VR that the FSM does not show as being connected. I will return/exchange the VR later today and see how that goes. Hopefully I didn't fry my new alternator by using this VR. (I think I will pull it and have it tested just to be safe.) I have a question for all you 240 electrical experts out there... the FSM on pages EE11 and EE12 talks about how the VR functions, and it specifically mentions a warning lamp. The schematic on EE12 even shows the lamp, and it's being connected to terminal L. However, the body schematic on page BE5 does not show a warning lamp, and in fact shows that the L terminal on the VR is unconnected. My chassis harness has no wire to the L terminal (and it looks to be unmolested original equipment), so I am inclined to believe that page BE5 is correct, and page EE12 is incorrect. (Also, I don't see any sort of alternator warning lamp anywhere on the dash.) So, for you electrical geniuses out there, how trustworthy is the FSM schematic shown on EE12 in regards to the factory VR? Can I safely ignore the lamp portion of that schematic and trust that the rest is accurate? Thanks in advance.

[NewZed]

Not an expert but ignoring Lamp seems reasonable.  The VR itself is probably wired to provide the current to the alternator windings from one of the other power wires, and the completion of the circuit from the harness is unecessary since there is no actual "Lamp" at the ammeter.  Sorry for guding you down the FSM path when it looks like it's not right.  Maybe this is why so many people just swap to an internally regulated system.

 

 

FYI, it looks like you could get factory part for $113.  http://www.courtesyparts.com/regultr-vo-p-283142.html

 

Here's a link to a thread from a guy who really knows the 240Z wiring.  He makes these for MSA.  Shows only five pins in the adapter.  http://www.classiczcars.com/reviews/showproduct.php?product=11

 

Here's another link showing all of the VR models that Nissan went through - http://www.carpartsmanual.com/datsuns30/DatsunZIndex/Electrical/EngineElectricalFittingParts/tabid/1630/Default.aspx

[Bob_D]

Hi NewZed, thanks for the hyperlinks. I have been eyeing the internally regulated conversion for a while and it's on my "someday" list. I really wanted to spend my money on more pressing items first, like new bushings in the suspension (mine are still original, and you can definately feel it on the freeway). But it looks like I may have to rearrange my priorities. The new alternator I got frfom RockAuto was a $20 closeout special, so I was hoping to get it working. Oh well...

[Bob_D]

Update: My RockAuto alternator tested out OK at O'Reilly's. Napa acknowledged that the part they gave me didn't match what was ordered, so another one is on order, should be in Tuesday-Wednesday. I found another blown fuse, 3rd down on left side, 20A labeled "IGN" and "Flasher". Replaced that and my gauges started working again! I will update again when the new, hopefully correct, hopefully solid state voltage regulator arrives.

[thebruce]

Good to hear napa took that back. Parts places are loathe to take electrical returns...

I would be surprised if your alternator cooked before it melted down your battery (figuratively, but just barely).

You might check your FSM, page BE 5 or so for the fuse value for that slot. Mine (1974) has 10A in the IGN flasher slot. Would suck to burn out a bunch of under dash stuff. I may be completely wrong as I am looking at a later manual.

Don't sweat the regulator if it arrives mechanical; they work fine, and have for a long time. The comparison of mechanical vs. solid state regulators is similar to points vs. electronic ignition. They use slightly different voodoo, but both work.

[Bob_D]

Well the new regulator looked just like the one that didn't work, so I got my money back and will try a different parts house. A buddy of mine who put a SBC in his 240 says he has his original VR in the parts box somewhere in his garage and will try and locate it for me. I also went through the box of old parts that the previous owner gave me when I got this car, and there was an old relay style regulator in it! The cover is riveted on, so I will drill out those rivets this weekend and take a peek inside. I don't think it was OE, as there are no identifying markings anywhere on it except a "Made in the USA" ink stamp. Also, very odd, but the white wire is cut and just hanging, and this does not corespond to the missing "L" wire in the chassis wire harness connector.

[Bob_D]

In the interest of completing and closing out this posting, after 2 moves (long story) I have finally gotten back to working on this car. I bought an internally regulated 60Amp 280ZX alternator and Dave Irwin's voltage regulator bypass plug (www.datsun-240z-upgrades.net) and guess what... it works! Perfectly! The Amp gauge shows a small amount of charge right after starting the car, as one would expect, and not the massive overcharge I was getting before. Conclusion: The external voltage regulators that the parts houses (NAPA, O'Reilly) are stocking are NOT CORRECT. The plug may fit, but the guts are not proper for this car. By the way, I cannot say enough good things about the quality of the stuff that Dave sells. In addition to the bypass plug I bought his headlight relay harness and parking light relay harness and the side marker conversion plugs. I have yet to install all this stuff, but the quality and attention to detail is first rate. I'd say "better than OEM". If you are sitting on the fence regarding spending the money, DO IT!