Glow plug relay override questions? - PeachParts Mercedes-Benz Forum

86Benzo300D · #1 03-14-2011, 04:26 PM

OK, I am going getting a ride 200 miles from my home to pick up my first Mercedes. It is a 86 300D Im pretty sure it is a cross year, but dosn't really matter for this forum.
So the guy I'm getting it from has been having trouble with the glow plug relay. He is a long time friend and does some quick not proper fixes on this that I am going to have to fix.
Well the fuse was blowing for the glow plug relay he increased the amperage of the fuse and it blew it again. So as of right now he has a nail were the fuse goes so it will work. Luckily he is not driving it like this.
I have done a bunch of research and am pretty technical when it comes to cars and electrical. So I want to perform the relay override with a ford fender mount starter relay and a push switch by my left knee like many others have done. I also what to put the switch to the dash light so it comes on when the switch is engaged. Here is the diagram of it from what I have gathered from other forums to the best of my knowledge. So can anyone verify this is correct or what i need to do to make it correct.

Diesel911 · #2 03-14-2011, 04:57 PM

Quote:

Originally Posted by 86Benzo300D

OK, I am going getting a ride 200 miles from my home to pick up my first Mercedes. It is a 86 300D Im pretty sure it is a cross year, but dosn't really matter for this forum.
So the guy I'm getting it from has been having trouble with the glow plug relay. He is a long time friend and does some quick not proper fixes on this that I am going to have to fix.
Well the fuse was blowing for the glow plug relay he increased the amperage of the fuse and it blew it again. So as of right now he has a nail were the fuse goes so it will work. Luckily he is not driving it like this.
I have done a bunch of research and am pretty technical when it comes to cars and electrical. So I want to perform the relay override with a ford fender mount starter relay and a push switch by my left knee like many others have done. I also what to put the switch to the dash light so it comes on when the switch is engaged. Here is the diagram of it from what I have gathered from other forums to the best of my knowledge. So can anyone verify this is correct or what i need to do to make it correct.

When I used a Starter Solenoid on my Volvo (see pic) The 2 heavy Red Wires on the Left are the (+) from the Battery. The single Red Wire on the Right goes to the Glow Plugs.
If you look close you will see a skinny Green Wire comming off of the 2 (+) Red Wires; that is the (+) Voltage going to the Switch and that other Green Wire goes from the Switch bringing (+) Voltage to th S terminal on the Solenoid Body.
There is no need for a Ground Wire because the Solenoid is grounded though the Bracket where it Blots up to the Fender Well.

That only leaves where to hook up the Glow Plug Light and a Fuse. I my case I have neither a Light or a Fuse in the System.

If I wanted to add a Light for the Glow Plug I would run a Wire from the Single Red Wire on the right side (the one that goes to the Glow Plugs) to the Light and there would need to be a Ground Wire from the Light to complete the circuit.

My Solenoid has a small S and an I terminal. Some only have one Terminal.

(The Red Wire that runs over the top of the Solenoid has nothing to do with the Solenoid.)

babymog · #3 03-14-2011, 09:46 PM

Although what you propose should work, if there is a short or other reason that the glow-plug circuit is drawing too much current, you could cause a fire (but you know that already).

Post more information about yourself, some of us have parts and help that we would offer, I even have a useable relay sitting in a box in the garage (works fine but the light times out early).

Diesel911 · #4 03-14-2011, 10:06 PM

Quote:

Originally Posted by babymog

Although what you propose should work, if there is a short or other reason that the glow-plug circuit is drawing too much current, you could cause a fire (but you know that already).

Post more information about yourself, some of us have parts and help that we would offer, I even have a useable relay sitting in a box in the garage (works fine but the light times out early).

Im my case I know that a short could burn something. That is why I said if the OP wanted to install a Fuse he could.
Also, in my case if a Fire did start remember it is only a Volvo; the Relay on my Mercedes is entirely stock.

vstech · #5 03-14-2011, 10:17 PM

I'd totally go over every inch of wires going to the glow plugs and verify none of them are frayed and contacting ground.
your wiring pic looks ok, except there are 6 glow plugs on an 86 300D

ah-kay · #6 03-15-2011, 01:46 AM

What you have done would work but I would not go that route. I would fix the GP relay circuit.

Pull the big plug inside the relay box and ohm the connector pin to ground. They should all read > 0 ohm but under 2 ohms. The connector connects to the GPs.

This is what I would do.

1) Never, ever put an over-amp fuse in the fuse box.
2) Put the correct rated fuse in the fuse box.
3) Remove the big connector in the GP relay
4) Try to start the car, just spin the starter, car may not start
5) If fuse blew then problem is in the GP relay or elsewhere.
6) If fuse does not blow then problem is the wires from the connector to the GPs.

Good luck.

Jim H · #7 03-15-2011, 07:59 AM

While your relay circuit will work, why not use about the same amount of time to see if you can find the short? Use a multimeter to check resistance of each GP wire at the relay with the GPs plugged in and then unplugged at the GP itself.

Any wires that still read LOW or 0 ohms are suspect. Trace these down and you may find insulation damage and the wires rubbing on 'grounded' engine parts. Then, assuming you find the shorted wire, you can re-insulate and use the MB relay that came with the car.

86Benzo300D · #8 03-15-2011, 02:46 PM

I will defiantly go through and see if their is a short somewhere, but from what my friend is saying he has checked everywhere with no luck. Also I don't know whats up with the year and model relating to the motor because it is a none turbo 5 cylinder I could be wrong about it being a 5 cylinder, but it defiantly does not have turbo. Even though I wish it did. Maybe it is a cross year I have been looking and unable to determine. I guess I will just have to wait tell i get the car. I am in the Reno area

86Benzo300D · #9 03-15-2011, 09:03 PM

Ok I am a dum a**. It is a 190D still very similar and it is a 5cyl. Non-turbo. Also after talking to him while he was sober he said that the fuse was only blowing every month. So it is a minor short, but that might just make it harder to locat. All find out soon enough can't wait though.

Diesel911 · #10 03-15-2011, 10:34 PM

Quote:

Originally Posted by 86Benzo300D

Ok I am a dum a**. It is a 190D still very similar and it is a 5cyl. Non-turbo. Also after talking to him while he was sober he said that the fuse was only blowing every month. So it is a minor short, but that might just make it harder to locat. All find out soon enough can't wait though.

Just make sure the Wires going to the Glow Plugs are not touching any thing. Give a special look where the Wires are bunched together with any sort of Clamp.
Look for a loose wire not connected to any Glow Plug.

vstech · #11 03-15-2011, 10:40 PM

Oh,
and let me be the FIRST to welcome you to the forum!
keep us posted on the progress with your 190D! and... we like pictures!

86Benzo300D · #12 03-16-2011, 03:27 AM

Ok I will throley check all wiring on engine harness and try to check under the dash if I can. How tight is it under there. Easy to take off? I going to order some new glow plugs bosch of course amazon has all five for 42 + shipping. Thanks