89 Audi 100 - No Start, Battery OK, What next?

Checking the ignition switch is a good idea. When you are doing that remove the electrical part of the switch (about a foot back of the instrument cluster) and try to turn it with a flat screwdriver. This is to check if the crappy pot metal tab inside the ignition that fits into the electrical switch has broken (the all do sooner or later).

Other ideas Remove the positive battery terminal and check if it is shorted to ground. If it is start following wires to find out where the short is (not a fun job).

I seem to remember that there is a controller (probably in the relay panel under the drivers dash) that shuts down all unneeded circuits when the starter is engaged. This is to provide max power to the starter.

Another thing to check is in the passenger side kick panel. The positive lead from the battery in the back has a splice in there where the main power splits for the fuse box and relays and for the starter. This splice corrodes over time and can cause all sorts of problems. A quick check to see if this may be the problem is to check voltage on the jumper location just behind the passenger side headlight. The voltage there should be within a half a volt of what you get at the battery terminal.

You might want to search on the AudiWorld T44 forum for other ideas.

Don't let the V8 worry you. that is the right place for the I5s as well.

Let us know what you find.

TonyJ Formerly four T44s Currently '04 A4 TQ6M

Like Tony said

I would charge up and test existing battery since it is too low to crank over the Audi. Then deactivate the alarm, I assume this is done by unlocking the driver's door. I am personally not fond of "jumping" the battery since it can put a shock on your system and may not work if your battery is too weak and the cables are not heavy enough.

You will need to look for electrical drains that caused the battery to be weak. Maybe a bad radiator fan controller which kept the fan on after you stopped the vehicle.

Just trying to get it started first to make sure nothing is wrong there and then start looking for why the battery drained down.

Checked the voltage at the jumper post this morning, and it's 12.45 volts. BUT, I opened the back doors to remove the battery from under the seat, and checked the voltage at the battery before disconnecting it: 5.5 volts! How could just opening the door bring the battery down this far? There is also a faint buzzing relay that fades out shortly after you open the door. The resistance from the positive battery cable to ground is about 1.8K ohms, so it is not shorted, Tony. Also the battery voltage is the same at the battery terminals, and at the jumping post, so I don't think it's the splice. Can't check the ignition switch until I get a good battery in place.

Took the battery to the auto parts store where I got it only six months ago - their load test says battery is discharged. They said the battery is needing a charge before they can test it again for warranty purposes.

But it is my feeling that there is a sudden, massive load on the battery, and Steve Sears on the Audiworld forum came up with a theory that a shorted starter fits all the facts.

Unfortunately, my trusted Audi mechanic will be out of town until Tuesday, so I can't get the car to him for diagnosis until then.

I am currently trying to get hold of a battery charger that works, since mine just blew up! If not, I'll take it back to the auto parts store and have them charge it up, and test it again.

I certainly appreciate your quick and useful replies!

Not to possibly burst your bubble, but that starter motor has a big fat relay in front of it that won't allow power to even get to the starter unless it has been "picked" by the ignition switch...

/daytripper '00 s4 6spd

Got a good charge on the battery, reinstalled it. Battery voltage is now

12.63 installed in the car.

Car starts! Charging voltage is 13.88 at the jumper terminal. Let it run for

30 minutes, turned off, restarted ok. Car is up to normal op temp, shut down, waited about 5 minutes, then radiator fan came on for 30-40 seconds. Then 5 minutes later, fan comes on again, but only for a split-second, then turns off. Hmmmm...

I suspect that there is a drain on the battery that is related to the radiator fan temp sensor or relays. This could account for the battery going down. I'll have my mechanic check it out next week, as I don't have the troubleshooting procedures for the fan controls.

So, Dave, you win! ( subject to verification by my mechanic next week! ) Thanks!

And thanks to all for your insights..you guys are great!

Thanks, tripper, didn't know that. Good information to remember in the future.

See Update below...

Glad it is back running! Yeah keep an eye or ear open for that radiator fan coming on with the engine off. You can also make sure that no trunk nor interior lights come on and stay on. I saw one vehicle with a drain that was in the vanity mirror. The light would not come on but there was still a drain there.

Your mechanic probably knows this but ...

The radiator fan is three speed controlled by voltages provided to is through a BIG resistor pack on the frame just under the radiator. These can go bad but usually do not.

Fan speeds one a two have separate relays in the main relay box under the hood just in front of the drivers side windshield. Fan speed three has a BIG double wide relay in the AUX relay panel under the dash by the driver's left knee.

Speed one is operated when the AC is turned on and if it is a turbo it runs during after-run cooling.

Speed two typically turns on and off if you are driving in traffic.

You would only hear speed three when the temperature is very hot. It comes on when the temperature gage is about ten degrees to the right of the center mark.

Any of the relays can cause the fan to run and take the battery down.

Two other components of the system to be aware of are a fusible link for the fan ground just below the brake master cylinder. The other component is the thermo switch that operates speeds two and three. It is located just below the lower radiator hose on the back of the radiator.

Say Hello to Steve Sears.

T> Got a good charge on the battery, reinstalled it. Battery voltage is now

Thanks, Tony, I was vaguely aware of how the fan controls work. The only thing I have noticed that is abnormal, other than the fan coming on very briefly when the car is off after a hot run, is that fan speed two has not worked with the a/c off for quite some time. For example, if I am in stop and go traffic in the winter, and the engine gets hot enough, fan speed three will come on ( sounds like an aircraft taking off! ) until the coolant temp drops below it's preset threshold. The engine never overheats, so this has not been a problem from a practical point of view, so I have not done anything about it.

However I usually have the a/c on about eight months out of the year, because it's hot and muggy in Houston even in the spring and fall. Fan speed one is sufficient to keep the coolant temp normal with the a/c on, and I'm not sure that fan speed two ever comes on when the a/c is kept on all the time.

I'm thinking maybe I should check/replace the relay for fan speed two? If the temp sensor were the culprit, why would fan speed three operate at all? Am I on the right track?

I'll send Steve Sears your greeting!

Have a great Memorial Day weekend...

Sounds lie you are on the right track in diagnosing the fan. I would suggest changing the thermo switch on the bottom of the radiator as it is most likely the problem with speed two. It could also be the fan speed two relay. You can easily unplug the thermo switch and jumper the connections to operate speeds two and three. If Two doesn't run then its the thermo switch.

However, given that your fan seems to be operating fairly well I would guess that your battery drain is due to something else. You could try pulling relays / fuses and checking for current draw with the ingition off.

I have let the car sit for three days without using it, in order to monitor the battery's state of charge.

Started out three days ago with a full charge of 12.63 volts. It is now down to 12.38 volts after three days of sitting. That's about a 0.25V drop over three days.

Measured the residual current draw at the battery cable connection to be

81.5 ma. This is with everything off, including interior lights. The only draws should be clock, radio memory, and alarm. Is this a reasonable draw? Might I still have a battery that is not holding charge sufficiently? The auto parts store won't warranty it, because their equipment shows the battery to be good, and it is only six months old.

Also, the radiator fan has not come on in three days, so I am ruling that out as a possible cause of a sudden discharge. I am puzzled as to what could have brought the battery to it's knees in the brief 10 minutes I was in the grocery store three days ago. Nothing was left on that would have drained the battery that fast. I can only assume that there is a fault in the battery, but I can't prove it to the auto parts store folks.

82 MA (I rounded up) is a *bit* high, but totally out of line. Generally you want it below 50 MA if possible. Consider also that some loads may come and go, so a current logging setup may be needed.

I remember hearing that batteries can develop internal shorts due to residue below the cells but that is only likely in the case of old or re-cycled batteries so probably not what you experienced.

A problem that the T44 series had that caused battery drain and the occasion fire was due to the battery being under the rear seat and close to the steel seat springs. The battery included a nylon cover that snapped over the positive battery terminal to insulate from the springs when people sat in the seat. If the part was not replaced when changing batteries there was the potential for problems. I am not sure if this is possible on your car but might be something to consider.

Let us know what you find.

I should slow down when I type, I meant to say:

"*bit* high, but NOT totally out of line."

IOW, it would be nice to be below 50 (or even better below 30), 80 isn't the end of the world.

Yes, I understood your meaning, thanks.

I am looking at the charging voltage of 13.88 volts, and thinking that's a bit low. Should be closer to 14.4 V. The alternator is a re-built Bosch that is about 14 mos. old. But, then I haven't started the car since Thursday, and today the battery voltage at the jumper post is 12.35. The original charge was 12.63 after a quick charge at the auto parts store on Thursday. Is that too much of a drop? I'm trying to determine if maybe there is a fault in the battery, like an intermittent shorted cell.

Other sources say that 75 ma is the max parasitic draw, so 82 isn't extreme. It wouldn't have pulled the battery completely down during the 10 minutes I was in the grocery store.

Is a puzzlement....

Stephen Clark knastet inn: :

To eliminate battery fault; Recharge, disconnect it, and do the same test as described above.

If you find no significant voltage drop, it's a leak elsewehere.

Hi Stephen, dropping 300mV in "at least" three days seems quite believable to me. Once charging has ceased (engine off) the terminal voltage will fall quite quickly to an open circuit value say 12.65V and assuming a capacity of nominally 40A/Hr a 100mA load would take approximately 14 days to fully discharge the battery down to say 10.5V My guess would be a week and the car might be hard to start? - so no obvious anomalies from your information so far.

14.2V is more suited to short runs than 13.88, depends on your normal trip duration whether your present voltage is a bit low. 13.65V is a "float" or continuous charge voltage.

Regards

Dave

Thanks to you all for your kind contributions. The battery is holding now at

12.34 volts.

I am beginning to think that what caused the discharge incident was an intermittent short of some kind in the electrical system somewhere, possibly the classic problem of the harness in the driver's door jamb. I have had trouble with the driver's window working intermittently lately, but it is working ok now.

If I happened to cause a short when I closed the door to go into the store that day, then that could have caused the battery to go flat very quickly. I don't know why a fuse did not blow, but perhaps the current draw wasn't sufficient to blow the fuse, but just enough to drain the battery. I suppose the battery was just too low to jump, or we had bad connections between the cars.

Anyway, that is my best theory to date. I'll either take a look at the harness wires myself, or have my mechanic do it this week. I'll let you all know what, if anything, we find.

Happy Memorial Day to all!

I spoke with my trusted Audi mechanic today on the phone, describing the incident, and what I had done to try to diagnose it. He says there is nothing wrong as the car stands today. He said if it were a short in the driver's door jamb, it would have blown a fuse, and I would have found smoke and burned wires. He further said that those circuits are not large enough to cause a failure like I described.

So I am left with an one-time mysterious event, that is undiagnosed, and will have to wait until a hard failure occurs to correct it.

So wish me luck that it doesn't happen again. Thank again to all for your suggestions.

Happy Motoring!