Alternator not powering battery

[Zed Head]

You have a 70 and a 75?  You're on the right forum.  Post some pics.

[Dave WM]

 

[Dave WM]

If the alternator is not charging, you should check to see that the field coil is getting voltage from the regulator, the FSM covers how to do this, a simple jumper from the Bat to the field coil will fully energize, you just want to make sure you don't rev the engine up (with the field coil un regulated the alt will put out excessive voltage likely damaging the ECU). Monitor the voltage at the battery and if it starts charging with the field jumped then the regulator or wiring to the regulator is at fault.

Edited July 1, 2016 by Dave WM

[Zed Head]

That's a great video Dave.  I had my BAT wire and Condenser backward.  So the original picture is not far off.  And the later alternators, or the remans, apparently don't have the plastic assemblies on the back.  My factory 1976 alt does.

So the OP might have the right alternator. Does your alternator have F and N molded in to the case?  Can he tell by looking if he has the right one?

[Dave WM]

it looks like the one I got from auto zone, should only be able to plug in one way, and yes IIRC the F/N is noted on the case of the alt. That one like mine replacement has the diodes inside the case, not under a plastic cover. like the OE Htachi. Can the OP please confirm the fuse links? do you have 2 boxes or just 1? and I presume you have checked all of them (you have to check continuity of the fuse link, looking at it is not good enough). Also check all the fuses in the fuse box, IIRC I was adjusting the VR and shorted something (the adj screw was hot) with my metal screw driver. This popped a fuse in the fuse box, killed some other stuff as well.

Edited July 1, 2016 by Dave WM

[siteunseen]

When I had the problem it was back charging through the IGN circuit, blew that fuse and killed all my gauges.  No tach or temp, volt gauge, nothing.

The original one at top, the newly remanufactured one on bottom.  

[siteunseen]

Look for a solid black wire on the negative side of the coil.  It runs from the distributor to the coil or vice versa? that's the tach signal.  I believe you have a blown fuse though.

Here's some helpful stuff for your car.  Look under ELECTRICAL then cleaning connections, http://atlanticz.ca/index.php/tech-tips.html

I think most vacuum leaks are a tear in the rubber accordian hose between the AFM and throttle body.  Some silicone will seal them up.

[jlenownnab]

thanks for taking the time to make the video Dave. We did check for continuity at fuseable links, we did check for blown fuses and had found one, lighter/clock. I will be heading down to my shop today and will check everything you guys mentioned. Should have it going shortly. Will keep you posted.

Stewart

[Zed Head]

Guess I was way off on the plastic doohickey.  F, N, S, and L will tell the story though.  Still some concerns about what your guy was looking for . He must have been measuring at the alternator, not the regulator.

Here's a test to bypass the regulator.  At least he can see that it works and move on to other causes.  There is a whole series of tests in the Service Manual.

Also, I'm pretty sure that the external regulator suppliers out there are iffy.  The solid state ones are sensitive, and the wiring changed over the years.  If you find that the alternator works but you can't get a good regulator you might go for the ZX internally regulated system.

 

 

 

[Dave WM]

IF the regulator is faulty, you can prob fix it. There is not much too it but points and coils. There are 2 relays, one is the charging relay (activated by the N lead from the alternator) It will latch if the N lead is generating any voltage (around 6-7v IIRC). for the 1975 its function is to prevent battery discharge I think, later models used that relay to operate the "charging" light on the voltmeter gauge (the 75 used an amp meter, so no charging light). The other relay is the one that does all the work of regulation, essentially duty cycle of the field coil of the alternator based on voltage output. as voltage rises it would open up to cut the field, as the voltage drops it would close the field circuit energizing the field coil. This happens very quickly so the points may be an issue. Make sure the VR cap (condenser) is in place to minimize the arcing that takes place from all the opening and closing of the contacts of the VR relay. This condenser is located up by the VR, there is also one mounted on the Alt this is more for noise suppression from the brushes of the alternator. If you do decide to buy a new VR (say the coils are open and burned out) I found one on ebay for about 35$ VR-159 I think is the part. There are SS versions of this as well, I opted for a mechanical unit. I really bought it just to see if that was the reason my autozone alt was barely able to deal with full load at idle. It was not. Don't know if its the reman alt (I took it back for another again just able to keep up) or maybe it was always marginal, but at idle with AC/lights/brakes/you can see the current move into the discharge side. anything above 1.1k rpm and its fine, and you are charging again.

Edited July 1, 2016 by Dave WM

[Zed Head]

18 hours ago, jlenownnab said:

 I have replaced the altenator, then the battery, then I thought maybe I got a bad altenator and replaced it again after getting it bench tested, then the voltage regulator in that order. Any ideas?? Thank you in advance.

The car came off the transporter barely running.

I have a car that still doesn't run. The tach lays all the way dead. 

 I hate to parrot your posts back to you but there's some stuff that's not clear.  Might help you solve your problems though.  Easy to get lost, best to get systematic when problem-solving.

It sounds like the engine does actually run.  You said the tach doesn't work and the only way to see that is if the engine is running.  Plus you can't really ID vacuum leaks unless the engine is running.  So you have an engine that will start and run on battery power, but you think that the alternator isn't charging.  How did you determine that?  Did you measure voltage at the battery terminals or are you using the dash gauge?

You also had the alternator bench-tested then apparently replaced it.  Most people would have the new alternator bench-tested right away just to save another trip.  Then you replaced the VR, so you must have assumed the alt was good.  So you should have a good alternator and a good VR but you're not getting voltage from the battery.  That might point to the power supply to the VR.  Which points to other areas, not necessarily the Signal wire.

So, if you went back to the beginning, what would you say the problems are, and how did you identify them?  I get the impression that assumptions are being made, and they may be incorrect.  We have a bunch of people here who have seen every odd problem, but we work best with the raw clues, not the decisions that have been made.  Your mechanic might be working on the wrong stuff.

[Dave WM]

Zed head is right about making assumptions. I was assuming a running car that was not charging the battery. A few things to note the "signal" wire will not make voltage unless the engine is running, its used to tell the VR that the alt is turning and ready to charge.