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  #1  
Old 03-22-2017, 06:01 PM
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87 300D No Tach, No charging no Idle control...

Not the Ovp. Not the voltage regulator, I have replaced both. There much be another part of this system I'm missing. I guess Ill take alt back off and take it in to be tested.

Car is not charging battery. Also the Tach is not working and the Idle control has stopped working. I checked any fuses I could fine. The test @ orielys claimed the voltage reg was bad, replaced it. old one didn't look that bad at all.

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  #2  
Old 03-22-2017, 07:28 PM
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Very simple test:

Somewhere in the vicinity of your battery, find the junction box shown in the photo. Flip the lid up to expose the three connections. Then turn the key on, but don't start the car. Measure the voltage between D+ and ground. You should have somewhere around 12V. If it's a bit less, this is ok. Zero is not ok. If you find voltage there, then the problem is the alternator. If you don't it's in the dashboard.
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87 300D No Tach, No charging no Idle control...-img_3170.jpg   87 300D No Tach, No charging no Idle control...-img_3169.jpg  
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  #3  
Old 03-23-2017, 11:16 AM
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A lack of both tach and idle control would suggest that the EDS system is not functioning. Either the EDS has failed, or it isn't receiving the pulse signal from the RPM counter on the crankshaft. Not sure how to test further, but if the EDS isn't working, the Tach won't either. Tach gets it's RPM signal from the EDS.

On your charging issue: When you turn the key to "run" for the idiot lights to come on, does your "Battery" light glow brightly? It should if the connections and bulb are all good. It serves as the "flash" source to get the alternator to come up quickly.
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  #4  
Old 03-24-2017, 09:39 AM
Diesel Preferred
 
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For years I battled a low charging voltage problem, which turned out to be a weak harness connection at the alternator. I took the harness connector apart (less than successfully, it was quite brittle but most of the pieces were still there when done) and used a pliers to clamp the teeth of each connector so they gripped more tightly, and the problem was solved.

CAUTION: Working near a running engine is DANGEROUS! Don't let any body parts or hair that you want to keep get caught in the serpentine belt or associated pulleys! Hot parts - don't get burned!

The definitive test: Car front up on ramps, hooked meter to the battery and placed on ground so I could see it from under the car, and VERY CAREFULLY wiggle the harness to the alternator from below the engine while watching the meter. The meter would jump from ~12.5v up to normal charging voltage (I think about 14v) as I moved the harness around.
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'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC
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  #5  
Old 03-24-2017, 11:05 AM
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X2 on checking the alternator harness.

Charging issues present on my 83 300SD, intemittent flicker of charging light at idle.
Recently the radio started rebooting when I'd hit a expansion joint while driving, then battery went flat on the commute home...fortunately before nightfall.

Purchased an Innova Equus 3721 Battey and Charging System Monitor (cigarette lighter port voltmeter) and saw voltage vary between 12.20V to 13.89V on the commute yesterday.

Wiggle test, with DVM on battery, confirmed that the poor alternator harness plug connection on my 83 300SD needs attention.
Engine vibration and roadway vibration cause the spade plugs to lose their grip.
It is on the agenda for this weekend.

Solid 13V plus on the 78 300SD when I drove it two days ago.
The alternator and connections were upgraded a while back.
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79 W116 300SD 'Stormcloud' RIP 04/11/2022
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  #6  
Old 03-24-2017, 11:21 AM
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All you need to do at this moment is the D+ test I described. It will identify whether the problem is in the dash or the alternator.

You have a problem with your EDS, true enough. It can be identified by reading the blink codes, as described in the FSM. My guess is that you have either a bad OVP or a bad crank sensor. But let's get the battery charging first.
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  #7  
Old 04-02-2017, 01:18 PM
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No battery light etc when turning on the key. 0 voltage reading at the posts D and B. tried various on and offs with the harness plug to alt, while wife turned on key, nope. looking up the eds system
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  #8  
Old 04-02-2017, 04:17 PM
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Took Alt off to test it, 11.2 volts. Changed regulator and still 11.2 volts. So, next step will be to replace that.
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  #9  
Old 04-02-2017, 05:14 PM
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Check the voltage regulator before you write off the whole alternator.

Sixto
83 300SD
98 E320 wagon
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  #10  
Old 04-02-2017, 05:34 PM
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Are you measuring at the right point? Replacing the alternator or regulator will do exactly nothing if you have zero volts at D+. And it's impossible not to read battery voltage at B+. If these readings are correct, they your alternator harness is toast.
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  #11  
Old 04-02-2017, 07:30 PM
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Quote:
Originally Posted by Mxfrank View Post
Are you measuring at the right point? Replacing the alternator or regulator will do exactly nothing if you have zero volts at D+. And it's impossible not to read battery voltage at B+. If these readings are correct, they your alternator harness is toast.
I took the alternator in and had them put it on the tester. I used the original Voltage reg and a brand new one I ordered. Both gave same reading. the older one looked great, so I'm doubting there was any issue with it, and I believe I replaced it not to many miles ago.

Still, I don't see how a low voltage on the alt would stop car from having battery light etc on dash with key turned on. The only light I'm getting it the glow relay. I also don't see how it would affect the tach.

So I'm thinking that even with a new alt there is a problem with the eds. I'll see if this gets the car charging, then move onto the eds. While I was in there anyways I went ahead and remove the radiator and fan, and replaced the belt tensioner, shock and pulley. (been making a racket for some time and at least its done.
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  #12  
Old 04-02-2017, 08:58 PM
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If this was measured on a tester, it's the tester that supplies D+ current. No D+ means no charge, end of story. If the dash light is out, then either the bulb is blown or the wiring is bad, either way, no D+. I'm still wondering if the measurement was done correctly.

The EDS problem is either a bad OVP or bad crank sensor. To diagnose EDS, you need to read the blink codes. I use one of these gadgets:

Mercedes Diagnostic Code Reader Tool W124 Obd1 300e 320e 400e 190e and others

There won't be blink codes at all if it's a bad OVP.
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  #13  
Old 04-02-2017, 09:07 PM
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Quote:
Originally Posted by Mxfrank View Post
If this was measured on a tester, it's the tester that supplies D+ current. No D+ means no charge, end of story. If the dash light is out, then either the bulb is blown or the wiring is bad, either way, no D+. I'm still wondering if the measurement was done correctly.

The EDS problem is either a bad OVP or bad crank sensor. To diagnose EDS, you need to read the blink codes. I use one of these gadgets:

Mercedes Diagnostic Code Reader Tool W124 Obd1 300e 320e 400e 190e and others

There won't be blink codes at all if it's a bad OVP.
Crank sensors is a simple check as shown in this helpful video... https://www.youtube.com/watch?v=7LTN1PlhDOY

Neat tester, I ordered one.
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  #14  
Old 04-03-2017, 06:45 PM
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Best thing to do is find a 1990 or later gas powered W124 at the junk yard.

Remove the alternator and the entire harness back to the terminal block next to the battery.
Get the terminal block as well.

Take alternator to FLAPS and make sure it works.
Put new Bosch regulator in alternator if it tests good.
If not take it back to JY and try again.

Remove your existing harness and alternator and terminal block. Replace with new parts. The gas engine alternator will fit in the same location and the pulley is the same size so your belt will still fit. The harness is a bit tricky to fit through the grommets but not too bad.

This solves your charging trouble in 2 ways. First the gas alternator has more capacity so your battery recovers quicker after glowing and cranking. Second due to the higher capacity the connections are bolted instead of plug in. This solves the intermittent connection problem.
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both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

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  #15  
Old 04-04-2017, 05:23 AM
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Location: Worcestershire in England
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Had a problem like this some time ago .
Found the problem was inside the rev counter .I unpluged the revcounter and it started up right away.
The revcounter message is sent to ucu .
No message = no start.

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