ignition switch or coil....?

[Dandi54]

Happy New Year.... well I've been trying to start my 380 for a week now. Finally got her fired up by putting 12v directly to the coil +. Now....where does thos take me....is my coil bad.....ballast resistor (can't find one!!)...maybe ignition switch?

Any help here is appreciated!! Feel like I'm almost there...........Thanks!!

Dan

[abiby]

The switch sounds like a good guess and changing it is relatively inexpensive.

Here's a link to an online copy of the MB service manual for the 107. You will be able to find a wiring diagram for your car there to help you trace down the issue.

Model 107

[cth350]

If you found the coil, you should be able to find the ignition module, which should be a metal brick. Keep tracing wiring and you'll find a pair of ballast resistors.

On the ballasts, there will be two leads going back into the wire harness. One will be 12v when you turn the key to "1" (the running state). The other gets 12v only when the key is in position "2" (turns the starter).

If that doesn't happen, then starting the car will be difficult. However, if turning the key to "2" at least gets the starter turning, then I doubt it is complicit in an ignition problem.

-CTH

[Dandi54]

Thank you both! I will attempt to locate the resistor which is a "suspect". I do see something which looks like a smalll temrinal block on the fender with green/yellow wires. If I can, with this aid of the diagram, verify that these are they, then maybe I can bypass and short 12 volts, across them to eliminate the switch as an issue. If the switch can supply the 12v, then I guess, you're saying that the ballasts are at fault.

[cth350]

If the bright green wire comes from the distributor to that block and then from there to the ignition module, so you're closer.

-CTH

[RadioTek]

The ballast resistors should be on your drivers' side fender, below and back wards of the coil. They should be 2 ceramic things about 1/2 inch square, and 2 1/2 - 3 inches long. One should be white(ish) and the other blue(ish).

Hope this helps,
Scott

[Dandi54]

OK...so I learned that the 82 has no outboard resistors...this changed in early 82. So, I began checking voltages and resistance on the basics...battery - voltage OK, coil secondary winding - ohms OK, primary - not. Primary s/b 3ohms but is 1.2...seems to me its the wrong coil. I know it was replaced by the prev owner a year or so before, so I'm wondering if because its the wrong resistance, maybe it deterioated and died on me, resulting in a crank no start cond. I have new champions in there and new rotor and dist cap....of course when I jumped the 12v to the coil form the battery it started right up. So, would you replace the coil with the spec unit...3 - 6 ohms? Could I try an old Bosch unit from my junk box which reads 3.5 ohms just to see if it works....would this damage my module? Thanks!

[RadioTek]

Do you have your battery voltage at the (+) side of the coil when everything is in the "normal" state? The (-) side of the coil is the 'switched' side of the circuit, so the (+) side is 'hot'. This should be a red/black wire.

If you don't have battery voltage there, you will need to find out where you are losing it. From what I see on the schematic, Fuse #5 is the supply for that circuit, so you might want to check that.

If you don't have power to that fuse, then the next step back for that circuit is the ignition switch. The switch assembly has 3 parts, the lock core, the wheel immobilizer, and the electrical switch. The switch is a replacable unit. It's a bit of a process to change out, but it is doable.

Given the age of the car, the switch may have gone out on you. Otherwise, you will need to look for wiring problems, such as bad connectors, pinched/scraped wires, or loose connections.

Follow the link in abiby's post to the schematic to get a better idea of the wiring.

Hope this helps,
Scott