What might cause constant "on" at coil?

[CZ-75]

Something has happened to my ignition system. I noticed a completelky dead battery, and while charging it, noticed that my coil got really hot.

Turns out thewre is constant power to the coil even with the ignition switch turned off.

I know this could be a bad ignition swith itself, but do any of you know the best way to diagnose this gremlin? I hate to tear into the steering column if this may be a more common issue such burnt out relay or ground somewhere.

 

[Jeff73Mach1]

I'd start by replacing the starter "solenoid" (it is really a relay) as if it is malfunctioning it might account for your symptoms, it is cheap, and it is easy to get to.

If your coil got that hot I'd also plan to replace it once you get everything corrected.

 

[pedstagn71]

I had one do the same thing and it was the solenoid that was the culpret

 

[CZ-75]

Thanks. I'll start with that. So in regards to the selenoid... Since I have upgraded to duraspark with a Accell Super Coil, will a 70's are OEM type replacement selenoid be OK or should I be looking for something more from the mid to late 80's?

 

[c9zx]

The OEM part should be fine. I ran the same coil with the OEM solenoid back in the 70s without a problem. Chuck

 

[Jeff73Mach1]

It is really just a great big relay.

 

[CZ-75]

The more I think of it, I don't know that the selenoid could be the problem. My mechanic buddy (who ran out of time helping me) snipped the wire coming from the ignition switch... snipped it yet the lead coming from the switch was still hot. I think that would eliminate the selenoid being the issue wouldn't it? Maybe not because of other hot wires going somewhere out of the selenoid that aren't supposed to be hot??

 

[TheRktmn]

The I post of the solenoid supplies 12 volts to the coil during start. When the key is released the coil receives 9 volts from the ignition switch through the 'pink' resistor wire. A damaged solenoid can indeed cause voltage to flow to the coil and 'backfeed' all the way to the switch.

The easiest test is to pull the small brown(?) wire off the I post of the solenoid and check that voltage at the coil drops to 0.

 

[piper62j]

When I look for an electrical drain, the first and cheapest thing I do is start pulling fuses.. it doesn't cost anything..

Leave the negative battery cable loose on the battery, but snug so it will conduct voltage.. When you pull it off and on, there will be a noticeable small spark, indicating a power drain.. With the cable snug, pull a single fuse and then slowly remove the battery cable. If you still have a small spark, that circuit is not the problem.. Repeat the procedure, one fuse at a time until you get to the one where there is no spark at the cable end.. That will be the circuit with the issue.

Trace the wiring back from the fuse panel to the switch, light, radio, clock (you get the idea) that is causing the problem..

Hope this helps.. It might save you some $$...

 

[CZ-75]

OK, so with the old coil removed (it was cracked from over-heating while charging), AND the ignition wire snipped...

I connected the battery. Used a volt meter with the negative probe on the negative battery stud. There was 9 volts coming from the firewall side of the ignition wire. The other wire from solenoid to coil was disconnected from everything.

Looks like my ignition switch isn't turning into the off position, or I have a short somewhere.

I wish we weren't going out of town this weekend... I'd like to get this straightened out.

Thanks for all your advice, guys! Keep it coming, and if the weather turns bad, maybe I can talk the family into coming home early since boating will be out of the picture.

 

[Chris Womack]

I had the same symptoms and found a short in red wires with blue and green stripes -- my harness appears to have gotten hot at one time and melted the insulation off. I ran new wire for my ignition.

 

[midlife]

Here's the proper way to check for shorts with the key off. These instructions were written for those who first install their wiring, but the concept works well for already installed wiring.

First, always install electrical wiring with the battery disconnected.

Physically install the underdash harness with fuses. Connect all underhood and taillight harnesses.

When ready to check out the harness, close all doors, turn off all lights, ignition key in the OFF position, accessories off, etc. Make sure both battery connectors are disconnected. Connect the positive battery cable to the starter solenoid. Leave the negative terminal disconnected from the battery. Then use a digital volt meter to measure the current draw across the battery. Place one probe of the DVM on the negative battery cable terminal, and the other probe on the negative battery post. Be sure that the DVM is set to amps, DC. If there are no shorts in the wiring connections, the reading should be on the order of 30 milliamps or less. Anything above 1 amp indicates some accessory is on; readings above 10 amps (may blow the fuse on the DVM) indicates a dead short.

If you have a short, disconnect all other wiring from the starter solenoid post where the battery connects and re-measure the current. If current drops, the source is the underdash wiring harness or the harness from the starter solenoid to the firewall. Reconnect the wiring to the starter post and then disconnect the underhood harness from the firewall and test again to isolate the source of the short.

If the short is not in the underhood or underdash harness, the problem lies in the alternator or voltage regulator. Disconnect each of these in turn to isolate the source.

If the short or high current comes from the underdash region, keep the battery negative side disconnected and remove one fuse at a time. Measure the current as above. If you now see low current, there is either a short or an item on that particular fuse circuit is on. Turn off that item and continue checking.

Eventually, you’ll have low current readings with all fuses installed and all wiring connected. This series of tests checks all of the battery directly powered systems. To check the Accessory systems, now repeat all of the tests above with the ignition key in the ACC position. The current with the key in the ACC position may be up to 1 amp or so. When all of the tests are done and no anomalous current is noted, at that time, and only at that time, is it safe to connect the negative battery cable to the battery.

 

[rottenralph]

Would a failing starter solenoid cause the starter to run longer(hang) than it should. In other words, still here starter for a short time after the motor already starts. My battery is also running dead but it is intermittent also.

 

[CZ-75]

Midlife you are awesome!

Turns out the short goes away when I remove the brown wire from the I post on the selenoid. This is the brown wire that was part of the duraspark wiring harness from NPD.

You all may remember that I had come across a known issue with these that supposedly I had fixed. Maybe not. I'll see if I can start over and get it sorted out.

 

[matrixx]

Would a failing starter solenoid cause the starter to run longer(hang) than it should. In other words, still here starter for a short time after the motor already starts. My battery is also running dead but it is intermittent also.

Yes, if it hangs bang on the solenoid top with your palm. If it stops then replace it. I've had them do it at random and I've also had them keep my car running after I turn switch off and take the key out.

The aftermarket ones are hit and miss while the ford parts tend to be better their lifespan is just not that long.

 

[CZ-75]

So I never had a chance to remove the wiring harness yet, but I'm really looking forward to pulling it, and "un-doing" the " correction."

Do you guys think I have it narrowed down to the harness, or could this still be an issue all the way back inside the steering column?

 

[Jeff73Mach1]

I think it is the harness/solenoid hook up, but that doesn't really clear it up. With the key in the off position, the "I" post should have no voltage measurable. That is the first check I would perform.

 

[CZ-75]

So... I got the problem fixed. Turns out it was the relay. The short went away when I disconnected the brown wire, but not because the harness was bad... It was because the ignition post was charged.

Anyway, I think I may have fried something.... Either the controller or the dizzy... The engine is missing.... Sputtering and coughing.

 

[Jeff73Mach1]

your coil is probably burnt up