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Discussion Starter #1 (Edited)
HI there boys and girls hope you all had a nice christmas. Went out to the mog this morning went to fire her up, cranked over 3 times, thought hhmmm, normally starts by now, then all the lights on the dash went out and the start button didnt work. Electrics is not my best subject! Any suggestions or help would be really, really appreciated as i need to go and get some logs with this damn unimog!!!

Cheers all:)
 

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If you're parking your Mog outside (and you confirm the battery is up to spec) , the first thing I would do with those symptoms is spin all the fuses in their clip holders. Sounds like you have a high resistance connection due to corrosion on the tips of those bloody $%#$%# open-frame fuses...
 

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BenzWorld UNIMOG statesman
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actually have heard of this.... and had it happen to me even though Im a 404.

CHECK YOUR FUSES.

Yep... clean them up with good electrical contact cleaner etc. Switch some around (keeping the right amps where they belong) and I bet your problem will go away or it will change places following a bad fuse around.
 

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Do simple stuff first. Check that the battery is working. How old is the battery? Check the cable connections to the battery, clean and tight? The carry through (where it going through the frame), on mine sometimes the bolts becomes loose, I get gauges but not enough energy to hit the starter. Sometimes corrosion can go down the battery cable and thin them out to the point where there is very little conductor left so it can't carry much amperage. Check the connections to the starter tight and clean? If that is ok, then try taking of the access plate on the drivers left side jumping the starter there to see if the problem hit be in the wiring somewhere else, say the switch or the starter button.
 

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Discussion Starter #5
Hi there, thanks for getting back so soon, yeah im running twin optima red tops so theres plenty of juice. Checked the fuses and emery papered them just to make sure they were getting plenty of current.
 

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Hi there, thanks for getting back so soon, yeah im running twin optima red tops so theres plenty of juice. Checked the fuses and emery papered them just to make sure they were getting plenty of current.
..be sure to do the same to the clips in the fuse holder.

So, do the dash lights (specifically the charge light) illuminate BEFORE you push the starter button, or is it stone dead ??
 

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Hi there,

My guess would be the insulation on the line that goes through the frame, to the battery. My first U900 had this problem. It seems like the most likely gremlin that could wipe out the electrical circuits. I'm not sure what the idea was with this design, but it had us stumped in the beginning. good luck.
 

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Hi there,

My guess would be the insulation on the line that goes through the frame, to the battery.
I agree - if your electrical system is TOTALLY dead, first check the through-frame connection. -OR- if you have a master disconnect, check the terminals for corrosion or a broken wire. I had some trouble with my 416 there.

No matter what is wrong, you should see some life unless your battery system is totally disconnected, shorted or otherwise drained below 7-8 volts. Voltmeter (or simple DC trouble light) time and progressive voltage testing at all junction points starting with the battery terminals themselves and moving toward the starter button.

Disclaimer - I'm a electrical engineer AND also play one on TV ;)
 

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Discussion Starter #9
hi there, there are no lights on at all on the dashboard. Its as if the battery isnt even on it. and only the side lights work. everything else apart from the side lights are dead!!! oh my god i need a wiring diagram!!!
 

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hi there, there are no lights on at all on the dashboard. Its as if the battery isnt even on it. and only the side lights work. everything else apart from the side lights are dead!!! oh my god i need a wiring diagram!!!
Ah Ha - so there is voltage INTO the system at some point. Which sidelights ? The 'parking lights' ? All those system run through the fuse blocks...

I'm still leaning toward fuse block corrosion...
 

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Petemate -

See your other thread, diagram posted but probably not of much use as barely legible. PM me and I can e-mail .jpg or fax.

Trip
 

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Side lights come on at first switch position, as do dash gizmos, and 'enabling' for starter solenoid. You seem to have ruled out fuses. Might be a bad main switch in first position. Try second switch position with headlights. Wiggle it around. Watch headlights. If headlights don't come on and the sidelights go off (due to heavy headlight current) then battery is dead or a connection is high resistance.

If headlights come on then you have connectivity to the battery. Push starter button. If headlights go out, again, battery is dead. Optimas can go dead too.

If headlights stay on, then battery is good and high current connections are good. Might be intermittent starter solenoid, fuse to solenoid, or wiring. It's at this point you need a wiring diagram.

Good luck,

Bob
 

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Side lights come on at first switch position, as do dash gizmos, and 'enabling' for starter solenoid. You seem to have ruled out fuses. Might be a bad main switch in first position. Try second switch position with headlights. Wiggle it around. Watch headlights. If headlights don't come on and the sidelights go off (due to heavy headlight current) then battery is dead or a connection is high resistance.
It might be the key switch, but I'm still confused as to what the 'sidelights' are...

Bob, unless I'm mistaken, dash instruments and idiot lights come on at key position 1 (this would include the charge light if engine is not running), parking lights are on at key position 2 and headlights at position 3. As you stated, you could start in any of the three positions. If you guys could clue me in to what the 'sidelight' is, I might be able to help more. Is this a CASE Mog ??

With the described symptoms and without further info, I'm *STILL* leaning toward a fuse block problem ;)
 

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I'll chime in, with reference to an un-named previous thread started by me related to wiring/fuse issues, that what at first does not appear to be a fuse issue in the end can turn out to be just that. When it comes to electrical issues and the Mog, I've learned to check and double check (or more) before discounting a potential problem.
 

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Check, 1. connection at both ends of battery cables. 2. Ground to frame and frame to cab. 3. Battery cutoff connections above throttle. 4. all connections at the fuse and junction block below it. I like to undo each on at a time and clean it so as not to mix up the connections. Use some dielectric grease when going back together. If you still have a problem, remove all fuses. Put them in one at a time, trying your switch in between each fuse. If one fuse brings the problem back, that circuit is the problem. HTH
 

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Discussion Starter #18
Yeah, the side lights are on position one on the turn of the key. Sorry about this thats what i call them or thats what people in the uk call them. Thanks for all your help and responses. im after some work shop manuals if anyone wants to share the love? If you do can you send them to [email protected]. Thanks.
 
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