Merc 500 shorted switchbox AND harness?

[swanstromdaniel]

Hi everyone, I am hoping that someone out there has experienced similar problems and can give me some advice! I have a merc 1400 and a merc 500 that i have ran interchangeably on the merc 1400 wire harness that is installed in my boat within the last year and a half. My 1400 went down for a rebuild so i installed the 500 on the boat and plugged the wire harness in. When i went to start it all i got was a solonoid click several times, and then the "ignition" wire at the end of the merc harness got hot and started smoking. The merc harness is in poor condition and needs to be replaced! I cut the power cables out of the harness (as had been done to my merc 500 harness in the past), and hooked the power direct to the engine to avoid the short. I re-tested and got the same results when I keyed it. before checking furthur I assumed that the harness short took out the switchbox?? I checked more and found that the switch box was going to ground at the red, white and blue posts, and certainly was not "open" as they are supposed to test with a meter. Is it possible for the harness to take out the switch box? Should i be checking the stator and trigger as well? what and where is the trigger? With power removed from the harness is it safe to continue using the harness for starter and ignition? Is it possible for the harness to still be shorting via the ignition wires even with power removed from it?(the reason i ask that is because i am questioning wether the switch box is really bad) Iv heard from several sources that there is no bench test for the switch box, but i found meter checks you can do on it. If the meter check says it is supposed to be "open" and im reading 1.8 can i assume it is bad??? Sorry for the length of the post and the amount of questions i certainly dont expect all the answers but any insight would be greatly appreciated!!

 

[swanstromdaniel]

Re: Merc 500 shorted switchbox AND harness?

BTW... The engine has no spark.

 

[Faztbullet]

Re: Merc 500 shorted switchbox AND harness?

The control box ignition switches are not compatable as you have found out due to 2 different type ignition systems the 140 was a ADI and the 50 is a CDI. From your post it sounds as if the switchbox is toasted and you need to check the driver as it in the distributor.

 

[CDI Tech Support]

Re: Merc 500 shorted switchbox AND harness?

i installed the 500 on the boat and plugged the wire harness in. When i went to start it all i got was a solonoid click several times, and then the "ignition" wire at the end of the merc harness got hot and started smoking. The merc harness is in poor condition and needs to be replaced!

Our replacement harness for this ignition is part# 414-2770 List price is $170.00. We sell direct or you can purchase through iboats.

I checked more and found that the switch box was going to ground at the red, white and blue posts, and certainly was not "open" as they are supposed to test with a meter. Is it possible for the harness to take out the switch box?

Absolutely the harness can destroy the switch box, especially if you hooked the White (from the harness) to the White terminal (on the switch box). That 4-terminal switch box is completely different than the 7-terminal switch box on the 1400 ignition. The 4-terminal switch box does NOT receive a 12VDC input, therefore, White (from the harness) is not used.

If you need it, we offer Repair & Return only on that switch box. List price is $288.00. Fill out this form before sending it in:

http://www.cdielectronics.com/rma_request.asp

Here's the switch box diagram for the 4-terminal switch box ignition on your 500:

Should i be checking the stator and trigger as well? what and where is the trigger?

The stator has a low-speed coil (Red terminal) & high-speed coil (Blue terminal) & can be checked here:

CDI Troubleshooting Guide

Shortcut:

Mercury 4 Cylinder - 333-3213

There isn't a trigger. The ignition driver is used instead & is not serviceable.

With power removed from the harness is it safe to continue using the harness for starter and ignition?

The only wire from the harness connected to the switch box is the Orange kill wire, which is connected to the Blue terminal on the switch box.

Is it possible for the harness to still be shorting via the ignition wires even with power removed from it?

If your harness is shorted, once power is applied, it can destroy whatever's connected to it.

Iv heard from several sources that there is no bench test for the switch box, but i found meter checks you can do on it. If the meter check says it is supposed to be "open" and im reading 1.8 can i assume it is bad???

Check our troubleshooting pages on this ignition here (it has diode checks):

CDI Troubleshooting Guide

Shortcut:

Mercury 4 Cylinder - 333-3213