Car died mid-journey. Alternator? Confused...

[CatsEyes]

Hi folks,

The other day, in bad wet weather, my 1996 NA's engine suddenly died mid-journey, leaving me stranded. She didn't want to start, but would do so every few times, for a couple of minutes, and then sputter and die, seemingly from lack of fuel. I had to get her towed.

At the time I assumed it was the reference sensor: the speed sensor had died in a similar manner six months ago (diagnosed by the good folks here). In each case the symptoms were similar: car cranked fine, and fuel was travelling through the system. But no ignition (except fitfully this time), and no tacho bounce when it wouldn't start. Also a low battery reading at the dash in each case, though the lights and stereo worked fine. So I ordered another sensor.

But today I had my first few spare hours, and the symptoms are a bit puzzling. The car started just fine first time, and got to normal operating temperature. On subsequent occasions, though, it started more shakily, and the battery reading was low in each case. And the battery reading continued to go down, as if it was discharging. But the battery itself seems healthy.

Some further background, which might pull these two confusing sets of symptoms together in a way I don't yet understand. (I'm still quite inexperienced at this stuff.) Recently my wife was driving the car, and turned on the air-con, when she noticed a strange smell, like burning. It went away again.

The next day the cooling fans went on full-blast at the 'on' ignition position, and stayed on like that throughout. I was troubleshooting that, and had purchased a new switch, when the ac/alternator belt started squealing one day out of the blue. Next day I turned it on and the squealing was accompanied by a thumping sound. I turned off fast. Turned out the ac condensor was missing a bolt and flexing. But what the thumping sound had been I wasn't sure: the belt operation, or the alternator?

So now I'm confused. Do I have a dead or dying alternator? Or a dead or dying reference sensor? Or both, unrelatedly? Or something else?

Any and all suggestions and advice appreciated.

[CatsEyes]

Oops. And one more thing. When the car has started with low battery indicator (10-12 volts) today, the cooling fans failed to come on at all.

[Guest765]

a dead/dying alternator won't leave the battery charged enough to restart the vehicle when it does run out of enough electricity to make enough spark to ignite the fuel. sounds like a mess in there.

i've had the problems with the fans sticking on and haven't been able to figure it out either; replaced the fan sensor and coolant dme temp sensor(unrelated) to no effect.

before anyone else posts it, check your grounds. your charge path is through your starter, check the connections there. check your voltage regulator on the rear of the alt. pull the alt and have it checked @ advance auto - they do this for free. alternatively you could use a multimeter with the car running. remove the belt and ensure the a/c clutch spins freely.

check the belt tension when you put it back on; your wife smelling burning when turning on the a/c tells me your belt is slipping - too loose. OR your a/c compressor is seizing. what does your idle look like when you turn on the a/c?

also after re-reading your post you say this happened in wet weather - check your starter connections and check the grounds in the engine bay, especially the engine grounding straps. feel for hot fuses while running to indicate a slow short.

[dangerous]

If your fans stay on, it is likely your fan relay. In the fuse box, the aluminum one in the back that is double the size of the other relays.

[CatsEyes]

Originally Posted by fwayfarer

a dead/dying alternator won't leave the battery charged enough to restart the vehicle when it does run out of enough electricity to make enough spark to ignite the fuel. sounds like a mess in there.

i've had the problems with the fans sticking on and haven't been able to figure it out either; replaced the fan sensor and coolant dme temp sensor(unrelated) to no effect.

before anyone else posts it, check your grounds. your charge path is through your starter, check the connections there. check your voltage regulator on the rear of the alt. pull the alt and have it checked @ advance auto - they do this for free. alternatively you could use a multimeter with the car running. remove the belt and ensure the a/c clutch spins freely.

check the belt tension when you put it back on; your wife smelling burning when turning on the a/c tells me your belt is slipping - too loose. OR your a/c compressor is seizing. what does your idle look like when you turn on the a/c?

also after re-reading your post you say this happened in wet weather - check your starter connections and check the grounds in the engine bay, especially the engine grounding straps. feel for hot fuses while running to indicate a slow short.

Thanks fwayfarer.

Checked the grounds already, but not the starter. Will do so. The voltage regulator was already in my mind: will look up how to test it. I'm also worried about the alternator bearings.

The belt tension is fine now, I think. As I noted in my previous, there was flexing at the A/C compressor, which caused the belt not to run straight. After I tightened it it actually started to come off. Maybe this caused damage to the alternator? But again: how does this explain the other symptoms?

Any other thoughts out there? I'm relying on the knowledgeable folks on this forum: neither I nor my mechanic have the necessary expertise!

[John_AZ]

CatsEyes,

Reading and rereading your symptoms....where to begin?

First, do not attempt to start the car or run the car with a low battery. You are going to or may have already damaged one of the electrical parts or the DME or your 9tuning ECU chip (sig line).

A low battery will cause more amps into the curcuit and burn out diodes, resistors, capacitors.
Porsche does not even want you to jump a car with another.
Protect the DME and electronics. Per WSM.



Does the car run better with the OEM chip installed instead of the 9tuning ECU chip? Maybe you damaged the chip program.

Check the alternator VR (voltage regulator). If the carbon "feet" are short or different length get a new VR. You should also pull the the alternator rotor out to smooth the VR slip rings on a lathe to remove grooves or risk damaging a new VR.

You may be lucky.
It could be the reference sensors ---you said not tach bounce.
It could be a faulty O2 sensor---unplug and try to run
It could be a faulty TPS--Do you hear the "click" when the throttle closes completely?
I could be a bad DME temp sensor.

Clean every electrical connection on top of the car and check for bad connections, frayed wires, shorts causes by burned insullation.

But first get the battery charged and check the alternator.
GL
John

[Guest765]

John - amperage drops proportional to the voltage level. The part about a low battery causing a larger amp draw isn't entirely true. Imagine the battery as a bucket full of water running into a hose. The voltage is the speed of flow and the amps are the volume of flow. As the bucket empties both drop in relation to one another.

[John_AZ]

That is not what I understand.

"when voltage gets low, the current must get higher to provide the same amount of power"
OR "Low Voltage creates higher Amperage".

An article of many. This article relates to motors (starters).
motorsanddrives.com - Electric Motors and Voltage

John

[Guest765]

John - that refers to a mains load not a battery. A dead or dying battery can't magically create amps - the chemical energy potential to do so is exhausted. This is why lights dim and fans slow when your battery dies. Re: laws of thermodynamics

[djnolan]

To check your battery health, trickle charge fully, and let the battery set without charging or discharging for 12-24 hours. Then check the voltage with a digital volt meter. A fully charged 100% battery should show 12.8 volts. if it is down to 12.4 volts it is only capable of holding half of it's rated capacity. Below 12 it is essentially dead. The reason the battery is not holding a full charge is due to sulfation (sulfur build-up) on the plates. This happens if the battery sits unused and undercharged for a long period of time (months, not years) If you are patient, a long trickle charge of several days will help reduce the sulfur buildup and bring the charge (and capacity) back closer to 12.8v. Running a battery with a significant reduced capacity risks damage to the electrical system, including the alternator. it also may not have the power to run accessories at idle.

If it is way below 12v then it may have a bad cell. You can check the voltage on each cell by wrapping a small piece of wire around one of your volt meter probes and dipping it in the battery acid while touching the other one to the post. Each cell should contribute 1/6 of 12.8v or 2.12v.

[MrTibbs]

Hi,
You've said it happened in the rain, and when you went to start it again it was dry, is that correct?

If so, it might be your DME itself (not the relay). Do you have any leaks (not sure if yours is under the carpets or under the dash. My parts car had a wet DME which meant it wouldn't start - the guy I bought it from said it was starting for a few seconds then dying. It never started for me even when it was dry.

A burning smell might be wiring frying itself.

Good luck - hopefully it's something simple and not a dead DME.

Mike

[John_AZ]

Originally Posted by fwayfarer

John - amperage drops proportional to the voltage level. The part about a low battery causing a larger amp draw isn't entirely true. Imagine the battery as a bucket full of water running into a hose. The voltage is the speed of flow and the amps are the volume of flow. As the bucket empties both drop in relation to one another.

Originally Posted by fwayfarer

John - that refers to a mains load not a battery. A dead or dying battery can't magically create amps - the chemical energy potential to do so is exhausted. This is why lights dim and fans slow when your battery dies. Re: laws of thermodynamics

fwayfarer,

I am not familiar with advanced electronics enough to give you an accurate answer. You have knowledge in electronics I do not have.

I only know that when someone burns out a circuit, transistor,+++ it is usually due to the cause and reaction of high or low voltage and current (amperage is measurement of current).
The voltage can be higher than normal by "jumping" a battery with another or using a fast charger to "jump" a car. Using a discharged battery to start a car can "burnout" car circuits.

Current causes the damage, not the voltage (high or low)

This is my simplified answer. Yours would be more technical.

This may not be the correct answer to use. I do understand your replies.

John

[djnolan]

Ohms law: Current = voltage / resistance (I = V / R) If R is constant and V decreases, then I (current) decreases.

[John_AZ]

Yes, I do understand.
Simplifying my answer. I will be more careful in the future.



John

[djnolan]

The lower the resistance, the more current that will flow. The variable is usually voltage, however. Also the amount of amps the power source can deliver has a whole lot to do with it. Once I got a wrench across an alternator terminal and ground. Talk about some sparks. Almost melted the wrench in two and burnt me pretty bad, too. If that had been a duracell instead of a car battery nothing would have happened. But a car battery can deliver mega amps and partially melted the wrench. That taught me to always disconnect the battery before working on anything electrical, or even getting close to anything electrical.

Think about crawling under a car and accidentally contacting the positive starter terminal with a wrench that was touching the frame or a ground. The sparks would fly like crazy and you would be lucky not to get blinded or burned. A car battery can deliver a lot of current and you don't want any body parts between it and ground.

Never mind a little damage to a DME.

[Guest765]

Originally Posted by John_AZ

Yes, I do understand.
Simplifying my answer. I will be more careful in the future.



John

john - not trying to put you down in any way, i'm an ******* about pointless things like that. you were right about the chance of damage, i'm just not sure the low voltage would be the cause, it would be someone improperly hooking up a jump to cure the low voltage - especially without fixing the underlying problem.

sorry if it seemed otherwise.

[CatsEyes]

Whew! A very high-level discussion while I was away!

OK, here's the update. Some half-decent weather, and I was able to get to work with a multimeter. The battery seems to be fine, as I reported in my earlier. Charging strongly. From memory, when it broke down and I tried to restart, the battery gauge gave varying readings. And also yesterday. But the multimeter readout seems strong enough (12.5v off to 13.5+ when on, from memory). I'd already checked and cleaned the ground, BTW.

I also used the multimeter to test the speed and reference sensors. The speed sensor (replaced at Xmas) tests fine at about 900 ohms. The reference sensor however gives exactly 158 ohms, suggesting it may be the culprit. There's one coming in the mail from your part of the world (I'm in Australia). On the basis of the earlier failure, I ordered it right away.

However, I'm still confused about the weird battery readings, and the fact that the cooling fans now refuse to work. (Will test the relay.) Finally, a new and worrying symptom: steam coming from the radiator area as the car warmed up. Just a results of the fans, or yet another thing to worry about?

My current plan is: (a) replace the reference sensor when the new one arrives; (b) get the alternator and voltage regulator looked at at that point. In the meantime keep checking the wiring. Any other suggestions?

John AZ: your pessimism troubles me. You're so often right...

[Guest765]

Battery is reading low. 12.8 is normal full charge. Do what was said earlier and trickle charge full and check after 24 hours. Steam from the Rad area is never good. Possible you've got a nice leak which has shorted out your fans and is the root cause of all this. Check fan fuses.

[djnolan]

Battery Voltage and State of Charge:

12.68v . . . . . . . . . . 100%
12.45v . . . . . . . . . . 75%
12.24v . . . . . . . . . . 50%
12.06v . . . . . . . . . . 25%
11.89v . . . . . . . . . . 0%

(NOTE: these readings are at 80 degrees F. Battery voltage readings will drop with temperature roughly 0.01 volts for every 10 degrees F.)
(At 30 degrees F. a fully charged battery will measure about 12.588 volts, and at zero degrees F it will measure about 12.516 volts.)

[Guest765]

Originally Posted by djnolan

Battery Voltage and State of Charge:

12.68v . . . . . . . . . . 100%
12.45v . . . . . . . . . . 75%
12.24v . . . . . . . . . . 50%
12.06v . . . . . . . . . . 25%
11.89v . . . . . . . . . . 0%

(NOTE: these readings are at 80 degrees F. Battery voltage readings will drop with temperature roughly 0.01 volts for every 10 degrees F.)
(At 30 degrees F. a fully charged battery will measure about 12.588 volts, and at zero degrees F it will measure about 12.516 volts.)

These are general voltage ranges for six-cell lead-acid batteries:

Open-circuit (quiescent) at full charge: 12.6 V to 12.8 V (2.10-2.13V per cell)
Open-circuit at full discharge: 11.8 V to 12.0 V
Loaded at full discharge: 10.5 V.
Continuous-preservation (float) charging: 13.4 V for gelled electrolyte; 13.5 V for AGM (absorbed glass mat) and 13.8 V for flooded cells

All voltages are at 20 °C (68 °F), and must be adjusted -0.022V/°C for temperature changes.
Float voltage recommendations vary, according to the manufacturer's recommendation.
Precise float voltage (±0.05 V) is critical to longevity; insufficient voltage (causes sulfation) which is almost as detrimental as excessive voltage (causing corrosion and electrolyte loss)

Typical (daily) charging: 14.2 V to 14.5 V (depending on manufacturer's recommendation)
Equalization charging (for flooded lead acids): 15 V for no more than 2 hours. Battery temperature must be monitored.
Gassing threshold: 14.4 V
After full charge, terminal voltage drops quickly to 13.2 V and then slowly to 12.6 V.

Portable batteries, such as for miners' cap lamps (headlamps) typically have two cells, and use one third of these voltages.


Looks like either answer can be correct, depending on temperature the most, and anything above 12.5-6ish should still be in a usable condition.