bypass strip fuse for glow plugs? - PeachParts Mercedes-Benz Forum

adamkat22 · #1 11-20-2011, 05:07 PM

i have a 77 240D and the strip fuse to the glow plugs blew. waiting for a new one to get in, but is it bad to just bypass that fuse temporarily? while waiting for the new fuse to arrive i wouldn't mind starting the car to check the alternator. there wouldn't be a relationship between a bad alternator and a blown strip fuse would there?

tbomachines · #2 11-20-2011, 05:44 PM

I always wonder what drives people to jump fuse connections, just in general. The fuse is there to protect the rest of the circuitry of an overload. If the fuse blows its either damaged (i.e. cracked) or it did its job. By jumping a fuse you're disengaging a fail-safe and putting the rest of your system at risk of damage and/or fire. So I wouldn't, simply based on principle.

On the alternator, take off the voltage regulator (two screws and black plastic thing on the back of the unit), which is a common wear/replace item. Check to see if the brushes are worn down, replace if necessary...its something that is cheap and easy to keep in the glove box should they wear down on the road. 90% of the time if you're getting a bad charge off the alternator on these cars its just the VR, no need to replace the expensive alternator as a whole unit.

compress ignite · #3 11-20-2011, 07:27 PM

Multiple EDITS:

The Worst ELECTRICAL risk you can take with a Diesel Mercedes!

MAN that's an 80 Amp Fuse!(VS corrected me, it's an 40 to 50 Amp)

(I Keep Two spares in the glove box.)

EDIT ! : 'Got all excited,The two spares I keep are the 30 amp for the Blower.
(124.128 HAS No Pre-Glow Relay Fuse.)

Photo credit goes to cphilip. (I would still be crying)

[AND,Yes having that Ugly Red thing in the Passenger Cabin is Like a Security
Blanket]

vstech · #4 11-20-2011, 07:45 PM

unless he's changed to pencil plugs, his 77 has a 50 or a 40 amp strip fuse... and IIRC, that fire was due to a bad blower motor...

compress ignite · #5 11-20-2011, 07:55 PM

(Blower Motor external Fuse is ONLY 30 Amp)

[Oh,Well Then... since the Glow Fuse is only 40Amp it must be perfectly O.K.
to Circumvent the Fuse's Safety Feature?)

Thank You (As Always) for the "Statement of Fact" correction.

WNC123 · #6 11-20-2011, 08:00 PM

you could always solder it. (JUST KIDDING!) i found this mess in my car. it's not there anymore.

buy a few spares. they are cheap in most places, even though i got ripped off the last time i bought some. i bought a couple more for under $1 in a recent parts order.

vstech · #7 11-20-2011, 08:01 PM

oh, I was not saying a smaller fuse would not cause a fire! I was just pointing out that the fuse for his car should be 50 or a 40, not an 80...

also, I was pointing out that the blower motor caught fire on his car (likely a 16 amp in a 123...) a wire rated for 5 amps can over heat and catch the plastic around it on fire easily destroying a car!!!
NEVER bypass a fuse!
if you MUST get your car started, go to the store and buy a fuse holder with at least #10 wire on it, and get a 30 amp fuse or get a maxi fuse holder, and use a 50 amp fuse for original loop style glow plugs, or an 80 amp fuse for pencil plugs!

adamkat22 · #8 11-21-2011, 08:06 PM

huh. i ordered an 80amp fuse to replace it cause thats what the replacement kit (fuse holder+fuse) i ordered had it sized for.

*************
you think it was supposed to be a 40 or 50 amp?

LISTING COMPETING PARTS SELLING SITES IS FORBIDDEN

vstech · #9 11-21-2011, 09:38 PM

if you have a 4 cylinder motor, and you have the original loop style GP's with the squiggly resistor wires, then yeah, 40 or 50 would be correct.

another reason to ONLY order mercedes parts from PHIL!!! fastlane is the best! (and it pays for this wonderful web forum!)

adamkat22 · #10 11-21-2011, 10:12 PM

well. i have a 4 cyclinder. that much i know. the glow plugs have a 'squiggly' solid copper running between them if thats what you mean. of course, they look like they were bent into shape with needle nose pliers in places, to make them fit, and i know that the engine was swapped on it, so i don't know for sure that they are the 'original loop' or just some make-it-work modification my friend did, but i'll assume the right fuse is 40 or 50.

unfortunately fast lane didn't seem to carry those fuses. unless i'm not looking correctly?? ::edit that. i found em on fastlane! but they also had the 80amp. whats a good resource for me to know fuse sizes for future reference...besides your brains of course.....

vstech · #11 11-21-2011, 10:51 PM

well, my brain is hardly a foolproof search, but it's available!

BASICALLY you just have to know.

a quick call to phil will confirm the right parts too.

if the wires between the glow plugs are indeed copper, then 80 amp is correct.
take a volt meter, and measure the voltage between one of the glow plug tips, and the block/head/negative terminal on the battery...
if it's 10-12v at the tip when the glow plugs are on, then 80 amp is correct.
if it's 2-4 volts, then the 50 amp fuse is right.

charmalu · #12 11-22-2011, 02:04 AM

Quote:

Originally Posted by vstech

unless he's changed to pencil plugs, his 77 has a 50 or a 40 amp strip fuse... and IIRC, that fire was due to a bad blower motor...

I remember that thread, that was a terrible loss.

as I remember, the consensis was, that the auxillary water pump siezing up would cause the PBU/CC Unit to short out the printed circuit boards, and that might have been the cause.

there was a rash of posts on installing a 1 amp fuse for the aux water pump.

Charlie