Pamela Anderson

My S4 drove well until I parked it several days ago. Now, as I turn on the ignition I hear the main relay snap, the normal dash lights appear momentarily along with the belt beep, but they fade to nothing within 1 to 3 seconds. I can do this repeatedly. There is certainly not enough juice to crank the car, I can't turn on the headlights and even the overhead cabin lights are dim.

Obviously, a bad battery would do this. Yet, I get 12 volts on a meter and when I connect my charger the gauge indicates a full charge. So..... I would welcome any experienced suggestions on where to start.

It seems like a corroded ground or ignition relay would not exhibit this particular symptom. Do you think that I've got a short somewhere that is grounding out the current? How on earth would I find that? Anything else?

Pamela Anderson

It's all about timing. As I waited for moderator approval I discovered this marvelous diagnosis regarding a similar problem. We'll see if "Hailers2" has my issue figured as well. I'll close this out or comment on my findings later.

https://www.rx7club.com/2nd-generati...-power-958657/

misterstyx69

iTrader: (142)

If you wouldn't have put up "that Photo" in your Profile,You would have been approved a lot quicker!
I stared at it for 3 hours..lol!..(just kidding!)

Pamela Anderson

"Hailers2" solved most of my problem with info from the link I noted above, yet there's still an issue and question at the end of this. So, here's my experience:

- I disconnected the 10mm bolt on the front side, middle of the engine compartment fuse box. The cable registered at 11 volts indicating a minor problem with the short positive cable from the battery. Clean and treat, now 12 volts.

- I disconnected the 10mm bolt on the back side, middle of the engine compartment fuse box. The cable registered at about 8.5 volts indicating a more difficult problem to find. I was doing the voltage check with the negative battery cable disconnected and measuring between the battery negative post and the disconnected fuse box cable. Clean and treat negative battery cable connection and starter connection, now 10 volts. Result: THE SEVEN RUNS AGAIN!!!

So, if anyone can suggest a method for me to find where I'm losing 2+ volts I would welcome the conversation. About a decade ago I remember cleaning probably two small grounds somewhere in the engine compartment, but I can't recall exactly. I'll get to that soon, but I'm doubtful it will resolve this.

satch

iTrader: (1)

Could you clarify the emboldened part above. When did you measure this cable and get 8.5 volts. Before disconnecting or after disconnecting?

Pamela Anderson

@Satch: I got 8.5 volts with the back side fuse box cable disconnected. After cleaning-up a few connections it jumped to about 10 volts which is where I'm at right now. As I mentioned, the car runs again, but I'm chasing that missing 2 volts as I expect it to be 12'ish volts.

Also, I'm measuring between the disconnected back side fuse box cable and the negative battery post with the battery cable also disconnected.

satch

iTrader: (1)

The front side connection, closest to the battery, powers the engine fuse box via the battery. The rear side, closest to the firewall, is powered by the Main Fuse that was powered by the battery. If this cable were disconnected it would lose voltage from the Main fuse. There should not be voltage on the rear cable when disconnected. This cable runs to the Ignition Switch to power it, the alternator output, and the interior fuse box to power the two 30 amp breaker fuses at the top of this particular fuse box.

Akagis_white_comet

iTrader: (4)

I'd like to suggest a few other tests to rule out other possibilities. First up, are you 110% certain that your battery is good? I had an autozone battery that was a few years old and would read a full charge on a charger and when not connected, but would drop like a rock when in the car. All of the parts stores stated it was good, but I wasn't convinced.

Each of the six cells inside the battery will read 2.1 volts when fully charged. According to EastPenn (makers of Deka Intimidator batteries), the following voltages indicate an approximate charge level
12.6 is Full charge
12.4 is 75% charge
12.2 is 50% charge
12.0 is 25% charge
Under 12.0 is dead
If it reads 10.5 or less, you have a dead cell.

Check voltage at the following locations, compared to voltage measured at the battery terminals:
Starter Positive terminal
Alternator output terminal
Starter Ground connection
Main Ground connection on driver's side strut tower

All are a straight line to the battery terminals with no fuses and should have less than 0.1v of voltage drop when compared to the battery. Here is a rough ASCII diagram of the power distribution system in the car

Battery+ -------Main fuse----All underhood fuses----Dashboard fuses---Target circuit

Start working your way back from the battery, going one piece at a time whole logging all of the voltage readings. A spotty connection will read inconsistent voltage or considerably lower than the previous ones. In all, there should be maybe 0.1v of voltage drop from the battery to the end target. Anything more indicates additional resistance caused by corrosion per Ohm's Law. Doing a resistance test on each link in the chain of connections is a wise idea as well. A good connection will yield about 0.06 ohms of resistance, while a poor connection will be significantly higher.

To correct this, follow this article written by Aaron Cake: Proper RX-7 Grounding Procedures

Something else to check for is parasitic draw. This is caused by the always-on devices that require an uninterrupted power source. Two examples of this are the stereo's memory and the factory clock. Parasitic draw is specified in the Factory Service Manual in the FAQs

Compare the battery's voltage when not connected to when it is connected, both measured at its terminals. Both should read 12.6. If it is more than 0.1v lower when connected, the battery is the problem as it was in the case of my autozone battery.

Should it be the battery, now is a good time to invest in a GOOD battery, preferably of the AGM variety. There are plenty of options, but the one I personally recommend is a Deka Intimidator. You just can't go wrong with one, as evidenced in Aaron Cake's Project Tina build. Mine is a 9A48 meant for a 6.0L Silverado. For a 20B FC with a 130A taurus alternator and marine battery terminals, some would say a Group 48 battery is overkill. I call it a 50lb investment in reliability

Pamela Anderson

Thank you two gentlemen, I presume, for thinking through this with moi.

Satch - I think there is a piece of information that I didn't include that lead you to your conclusion that I can't be seeing what I'm seeing. The positive battery cable is connected to the battery and the front side fuse box cable is also connected giving all of those peripheral main fuses (EGI, headlights, retractor motor, etc.) juice. So, when I disconnect the rear fuse box wire and put my meter between that wire and the battery negative post I've simply completed the circuit in a roundabout way. I hope I was clearer this time.

Akagis - That is a tremendous write-up and exactly what I was hoping to learn. I believe I confirmed a good battery by removing it from the equation. Now that I've drawn the battery down a bit I hooked-up my charger which was delivering about 1 amp and did my voltage check again. Still at about 10 amps. I was looking for those grounds just a short time ago and only found one, so thanks for the grounding link. It will take me until Monday to get to the other voltage tests, but I'll be back.

Thanks guys, Pam.

satch

iTrader: (1)

Placing the ground side of the voltmeter on the battery should still not cause there to be voltage on the wire disconnected from the back side of the engine fuse box. You can use the alternator housing as a ground source as well. Try this in the same test to see what you get. You would need some backfeeding of voltage on the disconnected cable to register voltage. Is the alternator from an S5,S6? And perhaps you placed the meter ground on the positive battery post by accident as this would explain the results you got.

Akagis_white_comet

iTrader: (4)

While the alternator's case would work for a ground connection, it depends on the starter having a healthy cable with clean, corrosion-free lugs on both ends linking it to the Main Ground location shown in Aaron Cake's article. Because it is subject to weather, salt and other nasties, I would just use the negative battery terminal as a known good ground point when testing for voltage at various points with a multimeter (set on voltage). Same thing goes with the positive terminal when testing grounds.

Limiting the variables in play to one at a time means an easier, quicker and more accurate diagnosis.

With all of the overlapping issues occurring simultaneously, I'm leaning towards the main ground cable being the prime suspect. It is the only item that ties all of the affected circuits together.

When I extracted the cables from my own 1987 GXL's Engine Harness (annoying to do, but pays off), both had several breaks in the insulation, dull terminals and were in poor shape overall. Despite reading as good in resistance (0.07 ohms) and being able to pass enough current to start the car without trouble, 25 years of Ohio winters made them unsafe for reuse. Both were replaced with new ones made from 4awg welding cable and lugs from DeLille Oxygen. The ground cable will have to be split into two cables, but 24" on both of them gives you a little extra working length. 48" for the positive cable to the starter is also long enough to have extra room to route the new cables properly.

The only other item I can recommend is to invest in Marine Battery Terminals. Aaron Cake refers to these by a different name, but they're Marine Battery Terminals that you can find at any Autozone or Walmart.

Pamela Anderson

I haven't finished everything that you suggested yet, but I may have found some things that show that you already solved my problem.

First, here's what I've done to get from 8.5 volts to 10.5 volts.
- Cleaned-up and treated all the grounds mentioned in that tremendous Aaron Cake link.
- Added a missing ground from firewall to transmission. Who knows which tranny job cost me that wire.
- Rechecked all my previous claims about where I see voltage and I was telling a true story.

Second, my problem was not as pronounced as I thought it was. When I say 10.5 volts it is from my simple analog meter, while the real reading is actually 12 volts if I had used my digital meter. When I said 12 volts (analog) it really was 12.6 volts (digital) as it should be. Sorry, I should have used the more precise device as soon as I saw you guys talking in 100ths of an ohm and 10ths of a volt.

Lastly, if you'd help a girl out because I'd really like to understand this, have we completely solved this problem now knowing the following? If I simply remove the negative battery cable from the post and do a voltage check between them with the ignition off, I get 11.36 volts (digital). If I now turn on the ignition to run I get the full 12.6. Not surprisingly, it's the same 11.36 and 12.6 if I go from post to strut tower ground. I'm guessing that I'm seeing a 11.36 voltage drain from those vampires like the clock and my stereo system, but shouldn't they register at 12.6?

Now that my wonderful car is running again and I see the full 12.6 volts with the ignition set to run, is my problem completely solved? Is my assumption way off?

You guys have been great.
Pam

Akagis_white_comet

iTrader: (4)

With the battery disconnected, it reads 11.36v at the battery terminals
Without a cable linking the battery's negative terminal to the Chassis Ground (Strut Tower), there is no return path for any circuit to the battery's negative terminal.

When disconnected and the key is ON (engine not running though), it reads 12.6v at the battery terminals?
Unless something is feeding power into the battery, such as the alternator (when engine is running), this is not possible. Can't happen without the negative cable attached either.

With every connection attended to per Aaron Cake's Grounding FAQ, there should be no discernable voltage difference between the Negative Battery Terminal and the Strut Tower's ground point.

There is a small naming error in Aaron Cake's article about the Transmission to Firewall ground. It is a capacitor for the Oil Pressure Sender and is wired parallel to the sender. I don't quite understand how it works (search for "Oil Pressure Capacitor" in the 2nd Gen section for more info), but it shouldn't affect anything except the Oil Pressure Gauge. The sender works by varying its resistance between the single wire attached to it and the engine block (ground) with the oil pressure. The exact scale for the sender and gauge are in the S4 FSM. The fuel gauge and its sender work the same way, both being known as "Resistive Senders". This is vastly different from GM's sensors being scaled on voltage instead (Capacitive). The easy way to tell the difference is the number of wires, as Capacitive ones require an input voltage. Map sensors such as the GM 3-bar one are a great example of this.

Sorry for the long side story, just wanted to clear up any misconceptions about the Oil Pressure Capacitor contributing to other issues outside of its related gauge. Most Second Gen owners are reasonably familiar with this matter, but I wanted to make sure you didn't have the wrong idea.

What are your voltage readings for the following conditions?
Battery disconnected (one or both cables off): Normal is 12.6v, see my previous post for charge level vs voltage for more info
Battery connected (Key set to OFF): Normal is 12.5-12.6v
Battery connected (Key in ACC or ON/RUN): Normal is 12.5-12.6v
Engine cranking (Key in START): Minimum is 10.0v, anything less and the battery is too drained
Engine running: Normal is 13.5-15.0v*
*Some alternators are a bit 'sleepy', making the multimeter read ~12.6v after the engine has been started. What I found on both my FD alternator is the subsequent Taurus Alternator is that they need to be revved to about 2500rpm once to wake up and get to work. After this, both read in the normal 13.5-15.0v range. Not entirely sure, but I think this behavior is called "Self-Exciting" (SOO many dirty jokes can be made about that, but that belongs in the Lounge )

I'm not sure about how the stock S4 alternator behaves, as it as the first part I swapped when I got my FC in 2007. All I can remember was that it was weak as hell and ruined the battery within a few months from repeated discharging. Upgraded to a FD alternator & got a new battery at Autozone and all was well again. Well, untill I ran that battery in the ground from not driving (discharged from parasitic load).

If you still have the stock one, I'd highly recommend swapping to either a FD or Taurus Alternator using one of the adapter pulleys offered by Mazdatrix or forum vendor Japan2LA. Japan2LA may have a few FD alternators on hand and would give you a nice price on a package deal. A pair of Marine Battery Terminals for $5 at Walmart/Autozone will also make a big difference in getting power to and from the battery. Got mine at Lowes for $1 in the discontinued hardware bargain bin and they've been awesome!

Pamela Anderson

Let me try to explain my question better. I was asking what I should expect to see when I remove the negative ground battery cable from the battery post. Then, I take my (digital) meter and place the negative line on the negative battery post and the positive line on the disconnected negative battery cable. This means that my meter has completed the circuit and I would expect to see whatever draw is required by the parasitic vampires and that number is the 11.36 volts I mentioned. Further, using this same configuration I now turn on the ignition and I get the full 12.6 volts (which is a good thing). My question was why I would only see 11.36 volts with the ignition off and should I just forget about this now that my car runs well again?

Regarding your other questions, are you asking for the load between battery posts? I know that I get 12.6 volts between posts with the cables disconnected. I would certainly expect to see 12.6 between posts with cables connected and ignition either off/acc/on as there's no significant drain on the battery.

Thanks for the lesson on the other stuff, but I have some conflicting info from reading other posts. Some people call the Capacitor an oil pressure condensor, but regardless of the name they all point to it being located on or near the clutch slave cylinder. Mine is actually on the strut tower and needed a good cleaning. Also, there should be another ground that runs from the top of the transmission (on my S4 manual, anyways) to a copper spade connector mounted on the passenger firewall. After a few transmission jobs it didn't surprise me that mine was entirely missing. If you can make it through all the chit chat, this is a good set of pics and Q&A.

https://www.rx7club.com/2nd-generati...d-help-851629/

It's a good day; I'm going for a drive.

Akagis_white_comet

iTrader: (4)

Ah, I understand what you mean now. Just so there's no confusion about polarity, it is generally better to use the meter's positive probe on the positive terminal and negative to negative terminal when doing a voltage test. There is no harm in flipping the polarity as you have shown, but it is a bit harder to follow.

In regard to the parasitic draw test, the meter in the configuration you state is that it is in series between the battery and negative cable. This can be done on either positive or negative cable. In contrast, doing a voltage test puts the meter in parallel with the battery (positive probe to positive terminal, negative to negative). All of the voltage tests I mentioned should be done at the battery terminal under the prescribed conditions.

When performing amperage tests, please be careful as most multimeters have a 10A limit. I cooked one last year because I didn't pay attention (tested while cranking lol). Caught the meter's PCB on fire (visible through the test lead ports). After the flames died out, it still works perfectly fine.

Assuming that everything is set up to test parasitic draw (meter on mA, 200 mA range), the 11.36 number would be 11.36 milliamps of current draw. Sounds a bit too low for parasitic draw, maybe you had it on the 20 mA range? 113.6 mA of parasitic draw sounds realistic for the car's age, though a tad higher than the FSM's specs call for. I think normal is around 60-90ma, check FSM to be certain. To find out which circuits are drawing power, place the meter so you can see it and pull the fuses one at a time, checking the meter each time. The suspect circuit will make the meter drop when its fuse is pulled and return to the previous number when reinserted in the fuse box.

Pamela Anderson

Those of us on the receiving end of all the assistance proffered by contributers like yourself is greatly appreciated. Sometimes I do struggle for a while searching for the right set of information, but when that fails you guys are a tremendous resource. Hmmm, with regards to adding new posts, wouldn't it be helpful if the various generation categories were further broken down into car components just like the FSM? Sounds like another topic, but I'm still sitting pretty again in my fav car thanks to RX7club.com. Now, on to re-tuning my TPS/idle/timing in case this newly restored flow of electrons has changed something.

In your debt,
Pam