Wiring the heater blower independently - PeachParts Mercedes-Benz Forum

Island300D · #1 12-29-2011, 01:06 PM

Hi all,
I've decided to run independent wiring to my new heater blower and connect it to an independent variable speed fan switch. Long story short, I'm happy to have only defrost and have torn out the climate system.

My question is, where is the best place to connect my positive wire? I'd rather not have to run it all the way to the solenoid or battery, and will have an inline fuse, but don't know if there is another positive terminal within the car that would avoid me having to run wire into the engine compartment.

I'm going independent because I have a blowing fuse problem with the existing wiring and can't seem to find any simple fixes within the maze of now defunct climate system wiring.

Any help is appreciated as the car has been garaged for a month now and I am eager to get her going again. Other than the damn climate system, she is in absolutely excellent shape!

vstech · #2 12-29-2011, 01:38 PM

no.
you will need to at a minimum run to the fuse box. nothing else in the dashboard has the amp capability to handle the blower draw...

the simplest thing to do would be to run to the fusebox inside the chase designed for all the wires, and tie into the fuse bar there.

Island300D · #3 12-29-2011, 02:25 PM

Thanks vstech.

My concern running to the fuse box has been that I want to avoid whatever short exists in the system currently that is causing all the blown fuses. And by the way, I did try out upgraded ceramic and glass fuses and they all blow, even with the brand new blower.

If the fuse box is fed by a single large gauge wire, as it would be on a sailboat (which is my area of better DC system mastery), then I can see that it would be fine to feed off of it and run the ground to a different spot, thereby bypassing the existing wiring.

vstech · #4 12-29-2011, 02:53 PM

it is fed with a large #6 or 4 wire, so yeah that would work, but the header for the box is common to that large wire, so any fuse position should work to feed your blower. BE SURE TO USE A FUSE!

Island300D · #5 12-29-2011, 03:33 PM

Excellent vstech.
Peachparts crashed and I don't have time to retype my longer reply, but thanks.

This should be straightforward, other than running the wiring through the firewall. I will indeed fuse the new line! The blower draws somewhere around 10 amps max, and the standard MB fuse of 16 amps should be sufficient to protect the wiring. I'll use 14 gauge which is rated to 25+ amps.

compress ignite · #6 12-29-2011, 07:25 PM

If You'll follow me for a minute...
1.You've Disabled/Disconnected/Cut the Wires between your former CCU and the
Blower,Fuse Box,Battery.
2.You've admitted to a possible Dead Short existing in the Wiring "Somewhere"
between the Laurel Leafed Star and the Rear Bumper,Bad enough that it blows fuses.
3.You've LEFT the Questionable Wiring INTACT (Still in the Chassis)?
4.Most Important...You've NO Idea WHAT'S shorting out WHERE to WHAT.
5.Sure sounds like an Electrical Fire Opportunity to me.

[Is there just one "Short" ? or a series? Is the cause insulation degradation?]

(Just another added benefit...You've posted such on an Internet Forum.
Think about the Insurance [Or it's Denial of Coverage] "Difficulties")

Diesel911 · #7 12-29-2011, 07:52 PM

Both My Mercedes and My Van have a Blower Resistor in them.

I do not know how it functions with the knob thar varies the Fan Speed but will he need to have one in His Circuit when he rewires?

vstech · #8 12-29-2011, 08:22 PM

Quote:

Originally Posted by compress ignite

If You'll follow me for a minute...
1.You've Disabled/Disconnected/Cut the Wires between your former CCU and the
Blower,Fuse Box,Battery.
2.You've admitted to a possible Dead Short existing in the Wiring "Somewhere"
between the Laurel Leafed Star and the Rear Bumper,Bad enough that it blows fuses.
3.You've LEFT the Questionable Wiring INTACT (Still in the Chassis)?
4.Most Important...You've NO Idea WHAT'S shorting out WHERE to WHAT.
5.Sure sounds like an Electrical Fire Opportunity to me.

[Is there just one "Short" ? or a series? Is the cause insulation degradation?]

(Just another added benefit...You've posted such on an Internet Forum.
Think about the Insurance [Or it's Denial of Coverage] "Difficulties")

he said he had a short that was blowing a fuse. and he's wiring directly to avoid the shorted wire, leaving that wire without a fuse, or power at all. I think that's safe, no?

vstech · #9 12-29-2011, 08:23 PM

Quote:

Originally Posted by Diesel911

Both My Mercedes and My Van have a Blower Resistor in them.

I do not know how it functions with the knob thar varies the Fan Speed but will he need to have one in His Circuit when he rewires?

he stated he's installing a blower control device to the direct wiring he is installing. it must have it's own resistors to lower the speeds on the blower.

Diesel911 · #10 12-29-2011, 09:54 PM

Quote:

Originally Posted by vstech

he stated he's installing a blower control device to the direct wiring he is installing. it must have it's own resistors to lower the speeds on the blower.

I hope He comments on that.

compress ignite · #11 12-30-2011, 03:31 PM

VS,

If "Zomezing" is blowing fuses I wanna know what it's cause.
(AND "Fix" it!)

Especially given this manufacturers propensity for "Minimum" Wiring specs.
AND all the equipment's Age!

What may have been perfectly acceptable in Sindelfingen 20-30+ years ago
CAN bring an Involuntary "Car-B-Que",Today.

Rats,Martens,Etc. add to the unseen dangers.

bricktron · #12 12-30-2011, 07:37 PM

> it must have it's own resistors to lower the speeds on the blower.

a modern alternative to resistors - not available in the '70s - is to a pulse width modulation circuit.