Car: 94 E320

A few days back, ASR/Check Engine lights started coming on intermitently. Then the car failed to start, clicking noise. Replace battery. Everything was good for a few days.

Then the car failed to start again. Jump started, had the battery and alternater check at Advance Auto Parts: both good. Drove around, came back, started fine. In the morning, the car failed to start again.

Ordered a voltage regulater from Phil Today.

What is the most likely source for drain?

This morning heard the AC blower with the key on, PBU was in the off position. The sound was very faint, so not sure.

__________________
Zafar
94 E320 58000 Miles

Hi zafar,----You may have "hit the nail on the head" with the blower motor running with key off. You have lost some "serious amps"in about 8 to 10 hrs overnight out of that new battery.Where there is amps (current) flowing, there is heat. With a cold engine, (overnight) & battery charged ,windows open & hood open,doors & trunk closed, listen for anything running,possible blower regulator with a "sick" transistor running at low speed.Also feel the rear of the alt for heat, possible a shorted diode. I use an infared temp tool , it works great for this test.If nothing is detected from the above checks,it's time for a DVM set on 10 amps (auto range) in series with the negative post & the grd cable. Read the amps or milliamps , approx .50 MA is normal current draw for modern cars with ECMs, body modules, radio (keep alive) & all modules have gone to sleep mode,usually after 20 mins. Start removing all fuses , one at a time, when the current flow drops down to normal, that last fuse you removed is the problem circuit.Now you know what "street" to go down, so to speak.That 600-800 amps is going out of them cables some- where, when you open the circuit with the fuse or possibly a relay, same deal, one at a time,from relay panel(rear of fuse panel),you have stopped the current flow & found your problem circuit. We know it has to be a circuit that is powered up all the time with the key off, so get a test lamp & write the numbers of the fuses that are "hot all the time", these are the ones that you are concerned with for now. Remember the only way to get to the bottom of this kind of problem is "Repairs through testing ", You have to fix it with " SMARTS NOT PARTS ". Please post your findings so all can benefit. Good Luck,----Ray

Last night checked the codes, DM Code 1, Pin 8 Code 1, but the check engine light is not turning off. Removed the key, check engine light stayed on.

Disconnected battery, after reconnection, the check engine light did not come on at all. Even with the key in the on position.

Went to DM, got code 1 again. Check engine light came on, won't go off.

Checked in the morning, check engine light was still on, with no key in the ignition.

__________________
Zafar
94 E320 58000 Miles

If your check engine light is staying illuminated with the ignition key removed then I would suspect the steering lock and ignition switch as a cause to your "current" problem. There is a pin between the lock mechanism and the electrical switch, when it is broken the electrical switch may not turn on or off correctly.

All the other lights turn on and off correctly with the key.

I rememberd one other thing. After replacing the battery, I checked the codes from pin 8 using the led/sw.

I did not insert the pins into the right sockets the first try.

Is it possible to damage the ECU by doing that?

I have misplaced Arther Dalton's schematic for the led/sw, so not sure what effect that would have.

__________________
Zafar
94 E320 58000 Miles

Another thought-the OVP relay might be sticking but I believe the ABS light would come on as well. Not cetain how you connected your blink tester, can it damage the ecu..........not sure about that, I suppose it's possible.

With the key removed test voltage at fuse 7.......if voltage is present I might suspect a broken ignition switch. I like to approach electrical matters one step at a time, in my eyes the switch needs to be confirmed or eliminated as a/the cause.

Luckily you have a voltage regulator coming, unfortunately this is also the likely problem. If your output voltage is 0 or very small, likely caused by a worn Volt reg, you are draining the car as you drive/use it. If the Volt regulator has gone bad, they are usually on/off, and you should not see any alternator charging with a spent reg.

All the electrical irregularities will probalbly go away, once the charge system is fixed and working normally.

In my experience, my volt reg went while driving during the afternoon, so I didn't notice it at first, no factory Volt meter in my 87300TD. So anyhow it starts getting dark and I flip on the headlights. Within about a minute, my abs light, check engine...all dash lights, come on the radio starts turning on and off, I mean it was wierd. Checked the output voltage and zero, pulled the volt reg and found the problem. replaced with new and she's back to normal in every respect. Now I have one less ashtray and a Volt, Boost and EGT gauges in its place.

__________________
Stable Mates:
1987 300TD 310K mi (Hans)
2008 Jeep Grand Cherokee OM642 165k mi (Benzrokee)

Voltage at Battery with the engine off is 12.4 and with the engine running it is 13.4.

I thought it should be around 14.5 V.

So looks like the alternater is working. The Advance Auto Parts testing equipment passed the alternater.

I believe I may have a combination of weak charging, along with a battery drain.

Should have the voltage regulater in a day or so. Hopefully that will resolve the issue.

__________________
Zafar
94 E320 58000 Miles

The charging voltage will drop from ideal due to temperature and/or load. 13.4 volts would only be too low with a cold alternator, no electrical loads, and a fully charged battery.

__________________
1989 300 SEL that mostly works, but needs TLC