New owner looking for electrical help

[Pagoda68]

I recently acquired a '94 E500 in need of work. The previous owner tried his hand at some "improvements", badly. Before I can even begin to try to correct the issues, I need to find out why it has gone completely dead. It was driven onto a flatbed and delivered to a parking lot where it sat for 9 days. Now, there is no voltage anywhere except at the battery terminals. The battery read 13v. but I put a charger on it anyway. I have no manual of any kind except a couple of Mitchell1 wiring diagrams a friend supplied. Can I begin with someone telling me where to find the main fuse? Or, any other guesses why it went from running to sincerely dead?

 

[gsxr]

Can you define "completely dead"? Does the starter turn engine, but the engine doesn't fire? Headlights turn on? Dash lights turn on with the key or headlights? Dash lights turn on until you try to crank the engine then the lights shut off when the key is turned? Etc, etc. Need more specifics.

There is no "main fuse" on any Mercedes. Some circuits are hot at all times. Double check the positive battery terminal, there are nuts on both sides, make sure BOTH are tight. The smaller 10mm nut is for wires which feed the powertrain computers under the hood. The larger 13mm nut is the battery clamp.

Click here for the factory service manual online. See Group 24 for the Electrical Troubleshooting section, which includes the complete ETM (Electrical Troubleshooting Manual), and all wiring diagrams / schematics. For M119-specific items, scroll down to the "Index" section within Group 24 and search for "119". Screenshot below.

Welcome to the forum!

 

[Pagoda68]

The car showed no voltage anywhere after the battery. No lights, no locks, no nothing. That's why I thought there might be a main fuse.

Thank you for the links. I did search the forum first but the older links had expired.

The 10mm nut seemed tight but I tightened it some more. Now, when I open the driver's door I get a beeping alert without any key inserted. There is no cranking. The windows work, and there is a blower sound, along with what sounds like a loud ticking clock coming from under the right side of the dash.

The clicking intervals were slowing. Just for the heck of it, I disconnected the ground and put a charger on the battery. We'll see what the morning brings. Maybe Santa will give me a cranking engine.

 

[gsxr]

Hmmm. That sounds really strange. How old is the battery? If there is no change after charging the battery overnight, I'd bring the battery to the local McParts/FLAPS to get it load tested.

 

[emerydc8]

Cold it be an alarm system malfunctioning? Isn’t there a relay for the disable function under the passenger side floor pan? A ticking noise in that area reminds me of this post.
Thread 'No start'
No start | Troubleshooting and Diagnostics

How about the fuses? Specifically fuse #5 that could look okay until you remove and inspect it.

 

[gsxr]

The car showed no voltage anywhere after the battery. No lights, no locks, no nothing. That's why I thought there might be a main fuse.

The 10mm nut seemed tight but I tightened it some more. Now, when I open the driver's door I get a beeping alert without any key inserted. There is no cranking. The windows work, and there is a blower sound, along with what sounds like a loud ticking clock coming from under the right side of the dash.

I'm confused here. You say "no voltage and no lights", but then the windows and blower work? Have you turned on the headlights? See if those work. With the headlights on, try to engage the starter. See if the headlights go out when you turn the key to engage the starter. This would indicate a failed battery with a shorted cell.

Cold it be an alarm system malfunctioning? Isn’t there a relay for the disable function under the passenger side floor pan? A ticking noise in that area reminds me of this post.
Thread 'No start'

The alarm system would allow everything to work normally, except the starter won't engage. Should have all warning lights on in the instrument cluster, etc. Sounds like he's not getting any dash lights, I think.

How about the fuses? Specifically fuse #5 that could look okay until you remove and inspect it.

YES. Check all fuses, especially #5. This cannot be a visual inspection. You must remove every fuse, clean the contacts, and re-install. There can be corrosion at the contact point which is not visible, but prevents current from flowing.

 

[Pagoda68]

Thanks for the suggestions. Battery was new 10/25. Overnight charge only showed 12.3v. BUT, the car started and the engine sounds good! Now I can start the list of repairs. I acquired the car in payment for a debt. However, the seller went nuts, stole the car and loaned it to some crack heads who got busted in it, and I got it back from the impound lot. So, there is no helpful info coming from the previous owner.

So far I've observed the rear suspension is down, the A/C and blowers don't work but the door locks, windows, and sunroof do. The turn signals and flasher work. The headlights don't come on but flash-to-pass lights them up. I suspect the odometer doesn't work because the trip odo shows 000. Radio is CODE. There are dash buttons I don't know what to do with.

Under the hood, the air cleaner is missing, replaced buy a kluge "low restriction" filter. Radiator is a Ron Davis but there is only one electric fan on the back side which was mounted very poorly. It does come on when the temp reaches 80C and stays on a bit when the engine is switched off. There is at least one unconnected connector and a few decidedly not MB wires. Near the right-side firewall, there's a plugged 10 or 12mm air hose that goes who knows where.
Because I don't really know what I'm looking at, the whole car is a mystery. What shop manual should I start with?

Most of the fuses are aluminum but look like new. I'm going out now and spin and clean them and their contacts.

 

[gsxr]

Yikes. Sounds like a major project. The owner's manual is in PDF format in the FSM linked back in post #2, that will explain the dash buttons.

You'll need to get the correct, stock air filter and tubes... check eBay. One aftermarket electric fan is a Very Bad Idea, you'll either need to go back to factory viscous fan clutch, or properly install a factory PWM fan from a mid-2000's Mercedes with aftermarket PWM controller.

Use the factory manual linked back in post #2, along with searching this forum. There are no other manuals available that will be much use. Most everything you need to do will be covered by the 20 years of postings on this forum... anything else, take photos and start a new thread with details about what you need.

Good luck!

 

[Pagoda68]

Cleaning all 23 fuses made a huge difference. Now the only inoperative electrical items are the right outside mirror, and headlights. Flash-to-pass works and all of the parking and signals work but no headlights (engine running). Now to tackle the SLS.

 

[gsxr]

For the headlights, after checking the bulbs and connector at the headlight itself... remove and re-seat the bulb monitoring module. This is the biggest relay in the relay compartment, behind the fuse area. Pull that out, check for dirty pins / sockets, and re-install. See if the headlights come to life.

 

[Pagoda68]

Pulled the relay and connectors look like new. No joy. The light switch seems to be suspect. Detents are vague. I can make the alternate side parking lights work, but not the headlights. The P.O. did several goofy things so I'm working on mysteries without any clues.
Are the connectors at the bottom of the headlight assembly for the light wipers? They are both disconnected.

 

[gsxr]

The rotary headlight switch should click neatly into each detent. If not... replace it. Not sure if that's the root cause of your issue, but the switch will only get worse if it's already acting up.

Yes, the headlight wipers connect underneath the headlights. If disconnected, one of the motors may be defective (either stuck on all the time, or blowing a fuse, etc). Not a common failure though.