MonoValve fuse ; which wire do I install it in - PeachParts Mercedes-Benz Forum

LNGfish · #1 02-23-2009, 03:05 PM

Since I'm installing a fuse for the Aux. Water Pump today I figure I might as well install a fuse for the MonoValve. First off since the switching is done on the Ground leg, read it in another post, does that mean I can install the fuse in either of the wires going to the MonoValve? There is Black/Red and Brown/white wire.

Is a one amp sufficient also for this application and which wire are U guys installing the fuse in? The black/red or the brown/white?

When I check resistance to ground the Black/Red reads continuity while the Brown/White reads 40 ohms. I guess this is right. Heats and AC run fine.

Further: (sideline)

I have a ballpark guess on why the power to the Aux Pmp has been causing problems.

I'll state here:

Well the plugs are very brittle after years and years. The load side of mine fell apart in my hand. Anway, if the plug falls apart and 12V "hits the hanger" that it sits in you have an instant short to ground.

I will put mine back together using some insulator PVC sheet gasket, in a U shape, inside this Grounded Plug Clip that holds the Plug. Anything that insulates should work.

Brian Carlton · #2 02-23-2009, 03:18 PM

Install it on the black/red wire.

One amp is perfect.

Jeremy5848 · #3 02-23-2009, 03:20 PM

I can't promise any expertise on the SD wiring system 'cause I've never worked on one or seen the schematics. However, it should be similar to the 300D (W123 and W124) that I have worked on, so . . .

You can put an in-line fuse in either of the two wires that go to the monovalve. My W124 schematic shows a black/pink wire as being the +12 volt wire so that would be the one I would fuse. Given that the monovalve is driven by a transistor in the PBU, it really can't sink that much current and the risk is primarily one of a wire losing its insulation and shorting to ground or shorting the two monovalve wires together. My preference therefore would be for some new tubing to enclose the monovalve wires but you can put in a fuse if it makes you feel better. An ampere or so should be fine.

Jeremy

LNGfish · #4 02-23-2009, 05:25 PM

I'm going to use 2 amp fuses for both the Aux Pump and the Mono Valve since I can't find a holder that holds a 1 amp at NAPA. I have (2) holders in hand with 2 amp fuses, do you think I will be OK with 2 amps instead of 1 amp for both applications?

My guess is it will be OK but wanted to ask. Thanks

pawoSD · #5 02-23-2009, 05:30 PM

Quote:

Originally Posted by LNGfish

I'm going to use 2 amp fuses for both the Aux Pump and the Mono Valve since I can't find a holder that holds a 1 amp at NAPA. I have (2) holders in hand with 2 amp fuses, do you think I will be OK with 2 amps instead of 1 amp for both applications?

My guess is it will be OK but wanted to ask. Thanks

No....go to radio shack and get a smaller fuse holder and some 1A fuses. 2A is too much.

I also don't think its necessary to fuse the monovalve....it can't really fail in such a way that it would hurt the klima. The main threat is the aux pump motor.

LNGfish · #6 02-23-2009, 05:34 PM

OK. I'll stop for the day and take these back to NAPA and head on over to Radio Shack tomorrow. I'm glad I asked.

Well atleast my battery tray looks good with a nice paint job and I have a handle on what to do tomorrow.

Thanks PawoSD for your quick reply.

charmalu · #7 02-23-2009, 10:53 PM

I bought a fuse holder and a pack of one amp fuses at West marine. The fuse holder is rubber, and the two halves snap together to make a water tight seal.
West Marine being a boat supply place, figured the best place for one.

It is bright yellow, would have prefered black though.

I couldn`t seem to find what I was looking for at the auto supply stores.

Charlie