Wiring a pump questions. - PeachParts Mercedes-Benz Forum

Austin85 · #1 12-25-2005, 12:26 AM

OK I have to wire my 12V fuel pump on the 300D. I have the pump and a relay was suggested to use .

One wire goes to battery. 1 to ground. one to power antenna; one to ???

What's the best way to wire my 12V pump so it starts up with the key turning on?

What gauge wire should I use?

JamesDean · #2 12-25-2005, 12:37 AM

I assume u have a 4-pin relay

wiring is as follows:

30 - Device (Horn,Lights,etc) Pump in this case
87 - Power Source (12v)
86 - Signal From Switch (ur case-power anteanna)
85 - GND.

I dont think wiring the 86 pin to the power antenna will get what u want (on when key is on) the antenna will only go up when the radio is turned on. You need to find a switched power line that comes on when the key is turned. I know where a switched power line is under the steering wheel. Its the red/black wire on the 14-pin connector. I cant think of anything in the trunk that comes on with the key....

Austin85 · #3 12-25-2005, 01:23 AM

That's the relay I have. Cool.
Now my antenna powers on with key I guess bacause so does my radio come on when the key goes on.
The power wire should be direct to my red terminal on the battery...
correct?
What thickness wire should I be using?
Thanks,
AA

JamesDean · #4 12-25-2005, 02:04 AM

Quote:

Originally Posted by Austin85

That's the relay I have. Cool.
Now my antenna powers on with key I guess bacause so does my radio come on when the key goes on.
The power wire should be direct to my red terminal on the battery...
correct?
What thickness wire should I be using?
Thanks,
AA

when i turn my radio off..the ant goes down (off)..and if someone turns the switch off it turns off...

power wire doesnt necessarily have 2 be directly to battery...any constant 12v power source will be succifient. for my relays i came off the dist. block with an inline 15-amp fuse then connected to the 12v constant power line

when i ran my lines for my relays i used 14ga. wire. I bought a 500' spool of it for $20 at HomeDepot when i was installing speakers...it was the cheapest way to go...i havent had any trouble with it.

Austin85 · #5 12-25-2005, 01:02 PM

Quote:

Originally Posted by JamesDean

when i turn my radio off..the ant goes down (off)..and if someone turns the switch off it turns off...

power wire doesnt necessarily have 2 be directly to battery...any constant 12v power source will be succifient. for my relays i came off the dist. block with an inline 15-amp fuse then connected to the 12v constant power line

when i ran my lines for my relays i used 14ga. wire. I bought a 500' spool of it for $20 at HomeDepot when i was installing speakers...it was the cheapest way to go...i havent had any trouble with it.

So if I use this relay with 4 connections and I DOn't go to antenna DO I have to hook up to all 4 connectors on the relay? or just 12V power ; fule pump red...and ground...btwComing off distributer block... What is that? Where is it?

sailor15015 · #6 12-25-2005, 01:17 PM

You can also screw the connecting wire directly into the fuse box. Under the fuses if you'll look there's screw holes and if you can find a screw to fit, its just a simple matter of using a volt meter to see which ones are only on when the key is on. Some will be on all the time, some only when the key is on. This is how I have my Vegtherm heater rigged up so its on all the time. The size wire that the heater needs is too big to fit under the fuses so I have a small wire running from the fuse box to the "power signal" connection on the relay. It works great, heats my oil before the IP right from the get go and I don't have to worry if I forget to switch back to dino when I shut it off because if the key's off, so's the heater.

JamesDean · #7 12-26-2005, 07:38 PM

Quote:

Originally Posted by Austin85

So if I use this relay with 4 connections and I DOn't go to antenna DO I have to hook up to all 4 connectors on the relay? or just 12V power ; fule pump red...and ground...btwComing off distributer block... What is that? Where is it?

The dist. block is located on the passenger side of the engine compartment...follow the main power line off the battery down into the engine area...ull see he block...its black with a cover...the 2nd screw in (from front of the car) is power.

if you do not hook up a line to 86 (switch) your pump will not run. if u connect a 12v constant power line to it....it will run always until the battery is dead.

you need to locate a line that comes on when the key is turned on. there is one under the steering wheel...

Austin85 · #8 01-01-2006, 10:24 PM

Quote:

Originally Posted by sailor15015

You can also screw the connecting wire directly into the fuse box. Under the fuses if you'll look there's screw holes and if you can find a screw to fit, its just a simple matter of using a volt meter to see which ones are only on when the key is on. Some will be on all the time, some only when the key is on. This is how I have my Vegtherm heater rigged up so its on all the time. The size wire that the heater needs is too big to fit under the fuses so I have a small wire running from the fuse box to the "power signal" connection on the relay. It works great, heats my oil before the IP right from the get go and I don't have to worry if I forget to switch back to dino when I shut it off because if the key's off, so's the heater.

OK Back here again....Does anyone know what / where is meant by "...screw holes"...under the fuses? I need to find this type of line that is on when the key is turned on. I have the pump installed next to the tank strainer hose; all the wiring; extra fuel hose and adapter; relay switch, etc. Appreciate the help.! aa

sailor15015 · #9 01-02-2006, 01:13 AM

If you take out a couple of fuses, you'll notice that there are some very shallow threaded holes. My wrekced car is the same as yours so look under the #12-14 fuses, I believe. You'll see some copper plating that looks like it connects all the fuses. That's where the screws are. You don't have to remove anything other than a fuse or two because I believe there is one under fuse twelve or thirteen. If this doesn't help pm me and I'll try to snap some pics for you. This is how I have some of my WVO stuff wired and it works great.

Austin85 · #10 01-02-2006, 01:00 PM

Quote:

Originally Posted by sailor15015

If you take out a couple of fuses, you'll notice that there are some very shallow threaded holes. My wrekced car is the same as yours so look under the #12-14 fuses, I believe. You'll see some copper plating that looks like it connects all the fuses. That's where the screws are. You don't have to remove anything other than a fuse or two because I believe there is one under fuse twelve or thirteen. If this doesn't help pm me and I'll try to snap some pics for you. This is how I have some of my WVO stuff wired and it works great.

Thanks, I'll try it...I just did all the other wiring for the pump.
I guess you're saying the screw under the 12-13 fuse is good to hook up to....AA