anyone know how to test an old square type switchbox?

[boltbreaker]

I'm working on an old Mercury inline 6 with a distributor type ingntion. It did not run when I purchased it so I cannot rule out incorrectly routed wires. It does not have any fire. It has the old square type switchbox with four color coded terminals on one side and three on the other. I know the keyswitch in my controls is good.<br /> I have no juice going to the coil either.<br />There is power going into the switchbox on one of the terminals.<br /> I think the problem lies in the switchbox, but am unsure how to test it. My clymer manual states to use quicksilver part # ^&*^%%^& to test the thing. I have three used switchboxes tried them all, and none work. I hate to dish out the money for a new switchbox without being 100% sure it's the problem. <br /> Are there any merctechs out there that know the "key" to the color coding on these, and a testing procedure?

 

[WillyBWright]

Re: anyone know how to test an old square type switchbox?

Since you know you have power to it, there are really only three possibilities. The amplifier, distributor, or the mercury switch. What you have is an amplified battery ignition system. The amps are as notorious for failure as are the distributors. What you need is a factory manual. I believe they are still available. The old Merc manuals covered all models for quite a range of years. I doubt the aftermarket manuals cover it very well. Unfortunately I don't have access to one right now so my contribution is rather limited. Somebody else will fill in the gaps.<br /><br />Since you tried different amps with no positive results, and you know it's getting power, the next logical step would be to disconnect the mercury switch. That's a brown or black cylindrical looking thing screwed kinda cockeyed on the silver front support bracket. It only has one short lead coming out of it. Disconnect that from the amplifier and check for spark. If you get spark there's something wrong with the mercury switch (kinda common). If not, then I'd suspect a problem with the distributor. But since the amps fail as well, I can't guarantee that all of those amps you tried aren't bad.<br /><br />I would also look inside the distributor cap and make sure the carbon brush in the middle is making good contact with the rotor. It is spring loaded and should move freely. DO NOT remove the rotor for any reason. It's molded to the shaft. All you can do is clean it. I should also mention to check the simple things like the belt. A shorted tach can kill the spark.

 

[Clams Canino]

Re: anyone know how to test an old square type switchbox?

Disconnect the distributor side of the switchbox (amp). Jumper brown and white teminals together. Touch the black to ground a few scrapes. With power to the switchbox (red and white +12) you should get a spark at the coil every time you touch the black<br />to ground.<br /><br />I'm betting it's the trigger in the distributor. It's easier (and cheaper) to get a used distributor on Ebay than to buy a new trigger.<br /><br />-W

 

[boltbreaker]

Re: anyone know how to test an old square type switchbox?

Clams procudure worked. It sparks every time with the jumper wire, and looks real hot. The trigger's are pricy boogers new. My catolog lists them for $300!<br /> I have a trigger from a four cylinder 850 with the same type ingintion system.<br /> Can I swap the two out if I change the metal "disc"? I also have the switch box from the four cyl currently installed. It says 4 and 8 cyl so I guess I need to change it over.<br /> It kind looks like a chore to get to if I don't remove the rotor, is it possible to do without removing the rotor?

 

[Laddies]

Re: anyone know how to test an old square type switchbox?

Yep, it will work but you must disasmemby the dist. from the top not try to remove the rotor, when removing the shaft use care not ot break the sensor off the hsg. an don't turn the plate over as it will screw up your timing---Bob

 

[Clams Canino]

Re: anyone know how to test an old square type switchbox?

What he said.... Use the body from the 850 and put all the parts from the 6 cylinder dist into it.<br /><br />You only need to change the box out if the tach is connected to it.<br /><br />-W