Voltage regulator???

[malibud]

1st of thanks for the help on my fuel problems. Now I only have 12 amps or less. I have the battery and alternator tested both are good. The alternator had been replaced at one time. I think i found it on advanced auto website it is listed as having a voltage regulator included but external and it is listed as 60 amps. Leaves me to believe it is the newer type. I think I am still running the old external VR. Would running two VRs cause my problems ?. How can I tell if the new alternator has a VR ? should I go ahead with the conversion as shown in this forum ?

thanks

Dan

[Wade Nelson]

First of all I'd need to know how you MEASURED that you only have 12 amps.

An alternator is only going to put out as many amps as it NEEDS to in order to keep the voltage at the set point set by the regulator, say, 13.5 or 13.8 volts.

Say you've got an alternator CAPABLE of putting out 60 amps, as confirmed when you took it off, down to Checker Auto / Pep boys and had them bench test it.

It's only going to put out that 60 amps WHEN it needs to --- headlights on, fan blower on hi, every accessory on, wipers on, fuel pump running, etc.

If you only have the headlights on and the battery is fully charged, it may only put out 5-10 amps --- just enough to run the headlights without the battery slowly discharging!

You don't need to do ANYTHING unless you're continually having a battery go flat, dim headlights, or some other problem indicative of a charging shortfall.

No point fixing ANYTHING that ain't broke is my creed.

Ball's in your court. Convince me your charging system isn't working exactly as designed.

[malibud]

The battery goes dead after running for 10 mins then no start up no fuel pump etc. The battery and alternator were tested good. I was going to connect the number 1 and 5 wires and the #2 and 3 as stated with the instructions on the alternator upgrade . But yes something is not working it will drop to 10 and so on until it is dead after about 10 mins .

[SteveJ]

To piggy back on what Wade was saying, test the output of the charging system by seeing how many volts it is producing. (Did you do that and find you have 12 VDC at the battery with the car running?)

The 70-77 S30s had an external voltage regulator. The alternator for these cars was rated at 50 Amps. The 78 was the first with an internally regulated alternator rated at 60 Amps. If you do have an external regulator with the internally regulated alternator, you will have issues.

You have left out a critical piece of information for us to help you. What year is your car? That will dictate what you need to try.

[malibud]

I am sorry it is a 75. It looks like I have an external vr attached to the newer alternator . There also is an external vr that is stock . After 5 mins of run time I am getting less than 12v at the battery and alternator

[SteveJ]

At what RPM? Even if you jumper out the external regulator, you will only get about 12VDC at idle, no matter how long you let it run. Get a copy of the 75 FSM from Xenons30. Look at the EE section of the manual to see how the alternator/regulator combination should behave. If you are sure you have an internally regulated alternator, jumper out the external regulator.

If was important to note what year Z you had because earlier Z cars require a diode to prevent feedback when shutting down the car. Yours should not.

[malibud]

Thanks well do I got the FSM but figured it would not cover alternator upgrade. Iam 90% sure i have an external VR in the car and on the new alternator. but if I by pass the old one in the car and the alternator does NOT have one what then can I damage anything or will I just blow the inline fuse ?

thanks again

[Zed Head]

The mass of relays and square metallic objects and wires and connections near the VR can be confusing. It sounds like you or someone else might have installed the wrong alternator on your car or you have the right alternator but should have replaced the external VR instead. 75 used an external voltage regulator. If you use the internally regulated alternator you have to disconnect the old VR AND install some jumpers at the VR connection.

You should get 10% more sure, to 100%, of what you have. There are drawings of the VR in the Electrical chapter of the FSM. The location is shown in the Body Electrical chapter (use the 76 FSM if you need to, the 75 xenons30 link doesn't seem to have that chapter).

Also, your ammeter will tell you if the alternator is producing. + is amps going in to the system, - is draining out.

The atlanticz link might help you help you out too, with pictures from a 77 280Z - http://atlanticz.ca/zclub/techtips/alternatorswap/index.html

[malibud]

OK Wade I think you were right and I am a dumb A$$ . I think so far it is all working I cleaned up the grounds and starter connections and all is good 12v at idle 14 at 2500 rpm. Now it runs great until it warms up and then it putters and back fires like it not getting enough gas... ideas? might need to start a new thread . I am going to investigate tomorrow...

thanks again for everyones help

[Wade Nelson]

If a fully charged battery goes dead (below 12.2 volts) in 10 minutes with the engine running its either not charging at all (fuel injected vehicle) or wired backwards (carbureted vehicle) so that the alternator is in fact DISCHARGING the battery while its spinning.

I once saw a Volvo S80? S60 with an alternator failure....that caused it to discharge a brand new battery, boy did it have ME confused --- you don't normally expect an alternator to do that, so I wasn't mindful of the polarity when I saw 40 amps, i ASSUMED it wasCHARGING at 40 amps, but it was DISCHARGING at 40 amps...

I suspect yo'uve got something incredibly simple wrong --- like the alternator leads reversed, ...so simple it's near impossible to see!

Can I suggest it might be time to get some help from a nearby shop rather than beat your head against the wall?

[FastWoman]

Wade, I would think almost anything is possible with a Volvo!! (Must have been a generator, not an alternator?) However, true alternators aren't going to work that way. They are going to produce the same polarity of output irrespective of the direction of rotation or field winding polarity. In fact the GM alternator on our Chrysler 318 boat was rotated backwards and produced the correct polarity. Polarity is all straightened out in the conversion from AC to DC by the rectifier bridge. The +12 output goes to the "ALT" post, and the ground goes to the case. It would be impossible to miswire it. Again, all bets are off with a brush-type generator, but an alternator should be pretty hard to miswire (er... unless the negative also went to a post, instead of the case? Would Volvo do something dumb like that?).

To me it sounds like malibud has a bad battery or some humungous short somewhere for the battery to drain down that fast. And I still wouldn't rule out a bad alternator. I would think even the '75 alternators should kick out 14V well before 2500 RPM. My '78 puts out 14V at idle, even when re-charging the battery right after a start. If I load the system with headlights and emergency flashers, then I get a bit of voltage sag until I come off of idle. While I realize both the alternator and battery tested good, sometimes the employees at the auto parts stores don't know how to test these things correctly. This wouldn't be the first time a bad part was tested as "good." You would think this would be such a costly mistake to them that they wouldn't make it!

Edited December 29, 2012 by FastWoman

[malibud]

Thats strange my alternator runs at 14V at idle then drops to 11 or so then at 2500 rpm goes back to 14. I have other problems like lack of fuel now to try to tackle so far no dead battery but I have not drove it much. thanks for the lesson in alternators.