cigarette lighter and radio not working?

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lman

New Member
Joined
Nov 17, 2012
Messages
9
Car
300 SE
hi

drove round part of M25 the other day hit a bump with offside tyres and suddenly the radio stopped working , no power at all. also the cigarette lighter isint working

is it a fuse? where is it located or has a cable popped out?

thanks for help
 
The first thing to do would be to read the manual to find the fuse and check it.
 
Hi, you dont say what year your car is? on a 91 fuse number 2 is for the radio, diagnostic term.6, hazard,vanity light, electric illum. control,front roof light and clock. Check if they all work or not, if not, the fuse box position would be in the manual (try in the engine bay in front of the brake fluid top up.)
Best of luck with it
 
hi thanks for help so far its a 1987 300 SE

so i checked the fuses, 18 which on the fuse card says is for the the lighter, the radio the glove box light all which are not working was bridged with foil. i replaced the fuse and instantly melted so perhaps its a loose cable causing a short or something or defective cable somewhere? any ideas what to do next where to start looking? thanks
 
also was thinking since the fuse was bridged with foil, perhaps a historical issue? even when i replaced the foil to re-create the bridge the radio/lighter etc would not work., what would cause the fuse to melt - an overload on that circuit i would assume?
 
Can you check the resistance across fuse terminals with multimeter with everything switched off?
 
If nothing melted when it was bridged with foil, but everything worked fine, then you may have put in the wrong fuse.
Failing that , the bump may have caused a short circuit somewhere.
 
just checked the foil, it was burnt where it touches the terminal. i set my multimeter to omega setting, touched the terminals and displayed 4.2m
 
4.2M Ohms across the terminals of the fuse box proves nothing, other than the insulation integrity of the fuse box.
On the same range of the multimeter, measure from the consumer/load side of the fuse to a good earth, with everything switched "on" (disconnect battery first for safety).
Though to be honest judging by your posts your not that familiar with using a multimeter, I would first be removing/disconnecting all the various things that are fed from this circuit, removing the interior lamps (bulbs) as these can blow and cause a dead short, and especially the stereo as this is the most likely point for any human incursion into the circuit, then with everything removed/disconected as described replace the fuse, if it still blows, further inspection of the specific wiring is required, if it does,nt blow then introducing each item back into circuit till the fuse blows again should then tell you what needs repairing or replacing.
 
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4.2M Ohms across the terminals of the fuse box proves nothing, other than the insulation integrity of the fuse box.
On the same range of the multimeter, measure from the consumer/load side of the fuse to a good earth, with everything switched "on" (disconnect battery first for safety).
I had the later measurement in mind but got mixed up in my head.
Anyway I would start with removing the radio and checking wires behind.
 
thanks andy - is there a specific earth point on the merc that i should use or do i need to run some cable to copper into the ground to create an earth as assuming the tyres get in the way. is there a way of telling which is the load side, and which is the supply?
 
Hi,
Just use a solid structural point on the car, a clean bolt or the like near the fuse box, the negative of your car's electrical system is taken down to the chassis, and use's the chassis as return path back to the negative of the battery.
You can check which side is the load side by seeing which side has 12V on it with the fuse out, you may have to have the ignition on as that fuse may only be live with the ignition switch on.
But I really think you should do the second test I mentioned, as all you are going to prove is part of the circuit has a short in it, which you already know as the fuse is blowing.
Your time is much better off spent in looking at the items in the circuit, specifically the stereo as Iand others have previously mentioned.
 
hi so an update that for fuse 18 it also lists the heaters for the windscreen wash jets as well as radio, cig lighter, and glovebox light...

my cousins husband rigged up a 12v battery with a light to test for a short, [he's an engineer for jaguar factory] we disconnected the bulb, the radio, and the cigarette lighter and still the bulb lit indicating a short?

so investigating the wiring sounds tricky, is there any places to start, someone else said maybe there is a bad earth somewhere, but i still thinking something has jolted going over the bump...
 
lman said:
hi so an update that for fuse 18 it also lists the heaters for the windscreen wash jets as well as radio, cig lighter, and glovebox light...

my cousins husband rigged up a 12v battery with a light to test for a short, [he's an engineer for jaguar factory] we disconnected the bulb, the radio, and the cigarette lighter and still the bulb lit indicating a short?

so investigating the wiring sounds tricky, is there any places to start, someone else said maybe there is a bad earth somewhere, but i still thinking something has jolted going over the bump...

The quickest way I have found is to use a cable tracker, they are used by IT and Telephone engineers and will save you a load of time. You can get them from Maplins, you can connect one end at the fuse and run the wand device over the cables (you don't need to probe them) the sound will change when you get to the short.
On the US they call them "fox and hound" do a search on YouTube for some demonstrations on how simple it is.
 

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