watchknut

So after 4 months and 2k miles of flawless driving, I experienced my first issue.

I was driving home in stop and go traffic, and I noticed my fuel gauge near empty...which was odd because it was filled up the night before...and a few seconds later the car died. Nothing when I turned the key.

The tow truck driver hooked up his jump pack and I got it restarted...we moved to a better place to tow it. When he removed the pack he said the alternator is gone that the battery wasn't getting anything back from the alternator. After a few minutes of idling, it died again.

I had towed to a local place that has worked on my Landcruiser. I talked with them today and they said they don't know what is wrong with it...that none of their machines can read anything and that the car messed up some of their equipment. This is all so bizarre since the car is so damn simple and I figured test an alternator shouldn't be too hard.

I told them to order a new alternator and install it...the car has been flawless running before this and the alternator seems like the obvious issue.

Is there something I am missing here?

The car has an upgraded S4 70 amp on it currently.

t_g_farrell

iTrader: (1)

First off, don't let others near it unless they know rotaries and old cars. Sounds like they hooked up digital equipment expecting 5 volts on some sensors and fried there equipment probably because 12 volts.

It could be the battery or the alternator or bad connections at the battery or grounds. Where you at in NC? I'm in south Charlotte if you need another set of eyes on it.

Heres the deal on this, if a DVM connected across the hot lead from the alternator to ground doesn't read at least 13 volts from the alternator, it may be bad. If it checks out then put the connection on the + side of the battery and see what it reads. If its a little less like say .25 volts compared to the alternator voltage then the grounds and connection are probably ok. At this point you may have a bad battery. You can get the battery tested or try charging it overnight out of the car to see if it takes a charge. If it does its probably good. The battery should take and hold at least 12.5 volts (all these numbers are what I use IHMO, the manual may say something different).

Clean all the battery posts and connectors for the battery and for the ground and hot leads going to the drivers side engine bay. Its amazing what clean connections can do.

The S4 alternator is a great plug in play upgrade for any 1st gen. I have a new one installed in mine.

KansasCityREPU

iTrader: (9)

Find a new repair shop. All that is needed to determine if the alt is charging is a voltmeter. The 1980 alt has an external voltage regulator. If the alt needs new brushes they are easy to replace and about $8.

You can find the factory service manual here: Foxed.ca - Mazda RX-7 Manuals

watchknut

Thanks guys!

Definitely finding a new shop for it, and I’ll call the tomorrow to letting them know what I learned on here.

watchknut

The battery is a new Optima Red Top, and the terminals were clean.

Banzai

iTrader: (13)

79's have separate voltage regulators, but aren't 80's internal to the alternators?

t_g_farrell

iTrader: (1)

Correct, 80s are internal, thats why the S4 alternator swap works well. So new battery and clean terminals. Yank the alt and have it tested. Simple as that.

Benjamin4456

Ha, I was just about to say that as well.

As t_g_farrell said, S4 alternators are a nice, plug and play upgrade for 1980-1985 cars. If it turns out to be the alt still, might be worth a look. On the other hand, I run an S6 alt and find it great. Not as straight forward as just plugging in the S4 but the rewiring isn't difficult. There are a good number of threads on the subject here if that's something you're interested in.

Edit: Just reread your first post op, didn't notice you already had an S4 alt, so you already know that I guess. Good luck regardless .

7aull

iTrader: (2)

As an aside, would consider new battery CABLES too. After 40+ yrs the originals are not very...efficient... anymore, what with corrosion internally and all. Saves a host of annoying, 'untraceable' electric issues too. Not avai new from mazda but lots of electric shops make up custom cables...

Stu A
80GS
AZ

watchknut

An update...

I sent an email that had the trouble shooting points from above and talked to them today.

They installed the new alternator but are saying that the car is throwing off too much power and they cannot hook up any equipment. The guy who has been a mechanic for decades says he's never seen anything like this.

I am going to pick up the car tomorrow and get it home and try to see what's going on. My father-in-law is a mechanic and hopefully when he comes over we can figure it out.

The car is so damn simple...I wonder if its the Mallory fuel pump or MSD ignition?

t_g_farrell

iTrader: (1)

That statement sounds like pure BS to me. Get it away from them ASAP!

watchknut

I am...it's really disappointing, as they are a local shop that worked on Landcruiser and seemed like a great place to do simple things on the RX-7.

I'll pick up tomorrow, get her home and see what's going on. The battery needs to last 5 miles.

Siraniko

iTrader: (13)

if this is an internally regulated alternator, all it need is an ignition 12v for alternator to start charging. if you look at the back or rear of alternator, connect a 12v on the upper terminal and start away. while the engine is idling, connect your voltmeter lead wire on the bottom terminal to check it if charging or not. most of the time, you many need to rev the motor to apprx 2k rpm for it to start charging.

mazdaverx713b

iTrader: (91)

If you are not mechanically inclined and or do not own or know how to use a multimeter, your first step should be removing the alternator and the battery and having them both independently tested. Most auto part stores will do this.

Any shop should know how to test the basic output voltage of an alternator with a multimeter. No equipment should be needed.

Replace the alternator and air pump belt when replacing the alternator as well. This is a great time to do so as all of the belts will be off. You can replace the a.c. belt as well if your car is equipped with a.c. battery terminals should be clean and tight and cables from corrosion and cuts or breaks in the insulation. Take the time to clean your grounds. Remember that a ground is achieved through the threads of a bolt, but also ensure that the ground wnd is clean. Ensure the threads on the female end are clean and ensure the bolt threads are also clean and free of corrosion.

watchknut

Picked it up today....they put a new alternator, spacers, and new belt.

When I cranked it up, the voltmeter in the dash read 12 and it fired right up. Flawless 15 minute drive home. After I parked it in the driveway, I came back a few minutes later and turned the key...voltmeter read 13.5 in the dash. I'll do the same when I get home and will keep everyone updated.

watchknut

Battery is almost dead again...wouldn’t turn over. I had driven it twice for 5 miles only hours before.

Buddy coming over with multimeter tomorrow and I am taking the battery back to Advance Auto.

Looks like I’ll have to dig deeper and see if there is a larger electrical issue.

mazdaverx713b

iTrader: (91)

Are you suspecting an electrical draw or a faulty battery? It wont hurt to have the battery tested and to check output voltage on the alternator.

t_g_farrell

iTrader: (1)

The bad alternator may have fried the battery, even a red top Optima. I just use the walmart brand and change them when they get 4 years old.