Hello,

So I have three alternators and two different batteries. The voltmeter continues to show that the alternator is not charging the battery, or isn't being engaged. I have some mechanical experience, but when it comes to anything electrical related I am at a loss. I haven't been able to get a solid reading of 12.5v from the alternator. I have took many readings, and it seems there is a voltage loss between the battery and the alternator.

I purchased this alternator from advanced autoparts. https://shop.advanceautoparts.com/p/...999%7CL3*15587

I didn't add that extra bit of wiring on the end it came pre-installed.

Some more info is that the tachometer reads in voltage on the dash instead of rmp currently, any way to solve this?

I've tried many combinations of different batteries hooked up, and taking many readings from different parts of the alternator and the battery. I'm just at a loss on how I can trouble shoot this. I can't seem to figure out a way to test the alternator itself out, because it seems that the battery being connected effects the reading i get when i touch the voltmeter to the alternator.

Located in toronto canada,
Thanks in advance

 

if you disconnect the battery while running, what happens? Does the car die? Have you tested the voltage with a multimeter? Come to think of it, a bad ground could be causing your voltage loss at the voltmeter/tach.

 

You make no mention of attention given to external voltage regulator your car has . They have a significant failure rate +age of car . I would look closely at it and the wiring to be a culprit as multiple alternators haven’t fixed the problem Regulators still available

FYI,tachometer reads as a voltmeter til alternator initiates charge then registers as a tachometer

 

Is there a way to test the regulator by using a voltmeter? What should I look out for in terms in readings?

 

that will be in the fsm.

Foxed.ca - Mazda RX-7 Manuals

if the foxed.ca site goes down try this one

Mazda RX-7 Reference Materials

 

Or, you could just buy a new regulator and swap it in. Not a bad spare to have around if it's doesn't fix it. One word of caution, this mentality sometimes leads to a severe case of parts hoarding, for which there is no known cure.

 

I have no idea what yer talking about,lol!

 

Aright so an update,

Car Dies, in the same fashion when it died on the side of the read while driving home.

When I put the tended battery in the car, the voltage meter reads 12.59 at the battery and 12.58 at the alternator with the car off. When I turn the car on voltage dropped to around 10.5-11 at alternator and keeps steady at battery but slowly goes down over time.

Thanks rxtasy3 for the links to the manuals, there doesn't seem to be an FSM for 1979 which has a seemingly different electrical system compared to the 1980's rx7 but i did look through and tried to understand the 1979 wiring manual.

Blow is a series of pics i took with some questions I have based on reading the wiring manual.

I am going to leave the battery plugged in tonight to see if anything is slowly draining it. I assume if the battery has lost significant voltage that there is a bad ground somewhere?

First picture, feels like a dumb question, but what part here is the regulator? Is it the large golden metal box in the top left corner?
If i were to replace it, is it safe to use an after market part from rock-auto such as this? https://www.rockauto.com/en/moreinfo...=1572&jsn=1572 or something different?


I found this wire unplugged, looking through the wiring diagram my best guess is that it is a b-10 vacuum relay, the cord was kind of long, located in a similar area and the shape seems to be the same.


Really not sure what this next unplugged cord is for... my best guesses are that it is A-03 hot start relay, B-06 air con relay, B-12 kick down relay based on the location and diagram with similar plug pattern


I believe this is the ground coming from the regulator, it had also been disconnected and was just floating there. I tried mounting it to some exposed metal on the car but that didn't change the behavior of the charging system when i turned the car on.



This orange guy wasn't connected to anything but also didn't seem as though it had any place for to be connected to either. I assume it is B-18 vacuum control valve (for m/t)



Lastly posting a picture of the fusible link X-07 as i noticed the battery was connected to it with a rather sketchy screw connection point. Any thoughts on this?

 

Pic 1-yes. Rock auto item ok to use
Pic 4 Noise filter capacitor,needs to be bolted down,on your particular year i can't recall, i'l look for a pic
Pic 5 sketchy screw is original to car

Alternator/regulator wiring diagram

 

A couple pics of the 79 GS, I purchased new. 40 years and 31K miles later, this is still factory configuration. Your pic #2, this white 3 pin connector is un-used. There is also 2 more un used connectors (both blue in color) in the same area. Also notice the taller voltage regulator. I've saw shorter ones like yours before, but I believe it was an aftermarket brand. You can also see where the noise filter mounts to the regulator.



Your pic #5. The orange connector is part of the "rats nest" emissions. Mine is not used, only the blue and white connectors are plugged in.



Your wire to the fusable link is correct, Mines covered by the boot.

 

Wow, thanks for the reference Banzai, I can't believe the condition of your engine bay!

So I just purchased an aftermarket regulator from rockauto, the one i linked earlier in the thread.

I also put the voltmeter to the battery which has been left in the car and it doesn't seem like it has lost any charge. Does this mean there no bad ground?

 

No it doesn’t,it means there’s no appreciable parasitic draw on battery when car is not running,which is a good thing.

 

Some good news, just installed the new regulator and it ended up working. Finally. Headlamps come on strong, battery is charging. I also noticed the the engine seemed to be running a lot smoother, previously it had a bit of a low slow pulsating, but now its much more smooth. Not sure if that has anything to do with the alternator/regulator or if it is unrelated.

Tachometer still won't read the RPM's. Stuck at 0 but all warning lights are off now, and seem to behave properly. With the previous set up the tachometer was functioning as a volt meter.

The alternator reads around 14v when i put the voltmeter to it and around 13.5v when I put it to the battery. This seems high? I believe I saw threads of people saying their output at the alternator was around 12.5.

 

Those numbers you got at alternator and battery are acceptable and will likely improve a bit as battery gets more consistently charged.
12.5 volts represents a 60% charged battery. 12.8 volts is 100% charged battery . Charging system needs to put out at least 1 volt more than battery voltage to be able to “push” voltage into battery.
12.5 volts measured at alternator is a barely or non charging alternator. Numbers you now show on your system are what is to be expected for the system to produce.

I’ts not your imagination the car idles better than before the charging system repair. It will run much better throughout the full rpm range,should be much smoother and a bit stronger.

The tach may start working now that charging system is operational. There are some tests you can do to make sure wiring to it is intact.

Good for you on getting the charging system operational, You will get to know your car better as you understand how its various systems work.

 

As GSLSEforme said, those numbers are exactly right, your charging system is working to spec or better. For the 0 tach make sure the tach sensing wire is hooked to one of the coils, for a 79 it may be the leading but not sure. I know for an 80 its leading because the 80 ignition turns off the trailing ignition at certain rpm/gear positions.