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Old 07-13-2010, 09:58 PM
Registered User
Join Date: Feb 2008
Posts: 23
C fuse blowing in 92 300E

Hi all,

My car keeps blowing the C fuse (rear door locks, rear pass compartment light, door lights, trunk light, and antenna). I have disconnected the antenna as it has been working intermittently for years and was hoping it might be the culprit. I was next going to check all of the bulbs and contacts on this circuit for issues.

Funny thing is the first time I replaced the fuse it took several days to snap. Now it goes immediately. Big problem is I cant get the fuel door unlocked to add fuel.

Any likely failures or advice would be greatly appreciated.


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Old 07-14-2010, 09:59 PM
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Join Date: Oct 2004
Posts: 3,546
The wires for the trunk light can break and short out at the hinge in the trunk. I've seen it a few times, it's worth a check. Seems M/B ran half the damn car off of that fuse. I hate when that's the one I have to diagnose.

90 300TE 4-M
Turbo 103, T3/T04E 50 trim
T04B cover .60 AR
Stage 3 turbine .63 AR
A2W I/C, 40 LB/HR
MS2E, 60-2 Direct Coil Control
3" Exh, AEM W/B O2
Underdrive Alt. and P/S Pulleys,
Vented Rear Discs, .034 Booster.
3.07 diffs 1st Gear Start

90 300CE
Milled & ported head, 10.3:1 compression
197 intake cam w/20 advancer
4 ignition advance
PCS TCM2000, built 722.6
600W networked suction fan
Sportline sway bars
V8 rear subframe, Quaife ATB 3.06 diff
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Old 07-19-2010, 07:33 PM
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Join Date: Feb 2008
Posts: 23
Gotten nowhere. Easy way to open gas flap when it is locked closed??

Well the C fuse is still going and I have checked the bulbs, connections, likely areas for faulty wiring, and disconnected components that might be causing it all to no avail.

So I am going to drive the car to my mechanic that is about 90 miles away. I have 1/4 a tank and think I can make it all the way up. If I need gas is there an easy way to open the locking gas door. This might be something nice to know anyway.

Last time I out a fuse in and unlocked everything as quickly as possible and got the fuel door open. Now the fuse goes instantly so I cant even get things unlocked.

Thanks for your help.
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Old 07-29-2010, 08:08 PM
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Join Date: Feb 2008
Posts: 23
Differential shot but electrics fixed

Hello All,

Well I got the C fuse issue fixed. I started hearing one of the relays in the back of the fuse box clicking after the car was off. After diagnosing and swapping in a known good convenience control module the relay stopped clicking and the fuse stopped blowing. I am going to replace the convenience module with the 202 superceeded part.

Bad news is we noticed a great deal of play in the rear differential. Way more than normal. Drained the gear oil and fished a magnet around and found lots of shrapnel. Thankfully we found this before something bad happened on the road.

Anybody have a good resource for used diffs, or reuilders (Bay area CA)? The benz rebuilt unit is about 1300 bucks at cost. I am trying some local junkyards but so far no luck. I did see a used one via adsit but not sure if it is the right one yet.

Part# is 124-350-39-74 if it is a benz rebuilt I think it would also have an 80 or 88 following that

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Old 07-30-2010, 01:48 PM
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Join Date: May 2009
Posts: 398
Also if this happens again you can open the gas tank from the trunk by pulling the plunger from behind the carpet.
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Old 08-01-2010, 12:07 AM
ashedd's Avatar
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Join Date: Aug 2008
Location: Seattle
Posts: 1,790
So I got my new 400E home today and was looking under the hood...
C fuse blown. Found another red fuse and popped it in... I gave myself a small 3rd degree burn on my finger. Complete with the smell of burnt skin... my own burnt skin

I was going to check out the trunk light tomorrow and go from there. We did notice the lamp out light on when we had the car running. So perhaps my convenience module is bad too.

Anyway now I know to give it a look. Thanks

08 R320 CDI current

95 E420
87 300D Turbo 5spd
90 300TE
83 300SD
85 300TD
92 400E
85 190D

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