Turn Key off, truck runs...

[muddpile]

Well, I think I'm nearing the end of my Painless harness problems. My newest thing is that when I shut the truck off with the key, it continues running until I pull the power wire off the coil on the HEI. Is there a simple explanation for this, because I can't figure it out, as the ignition cylinder just plugged right into the harness. Thanks!

[t korinek]

Sounds like you bypassed your ignition switch & just have straight power to your hei. Make sure the wire running to your HEI out of the fuse box goes dead with the Ignition switch off, If not find one that does.

[eric67m]

Check painless's website forum. I believe that you need to put a diode #276-1661 from radio shack on the one of the wires to the alternator. I think it was the white alternator exciter wire, but I would check the website. This diode is like a one way valve to prevent the alternator backfeeding voltage to the rest of the system. Easy crimp/crimp and my problems were solved. They should put the information into the installation manual.

[c10addict]

I HATE PAIN-IN-THE-A$$ WIRING HARNESSES!!!! I bought their tune port harness for my 68 and could not make it run... I went through wire by wire only to find they had three wires swaped in various connectors throughout...
I cut it up in chunks and sent it back to them.... Bought Street and performances harness and everything was great!!

Ok I'm off my soapbox now!

[sneakysnake]

Hooking to the wrong terminals on the solenoid or not using a "ALT" light on the charging sys and using an electric fan without a relay can cause this problem.

[mtdave2]

check to see if your battery cable has melted to the exhaust...been there done that!

[Musclerodz]

If you have an internal regulator alternator installed, you need to install the diode as mentioned in the post above. They will backfeed power sometimes when the ignition switch is turned off and keep running.

Mike

[mrein3]

Others are right. You are getting 12 volts from something back to the ignition wire that feeds your HEI.

Over the years I converted my truck to HEI. After that I converted it from non AC to AC. When wiring up the AC the factory relay that ran the hi-speed fan on the donor truck was dead. I figured no problem, I'll just plumb in a different relay. I wired it so the hi-speed wire from the fan switch went to a relay. The hi-amp wire from the battery to the relay came off of a 2nd junction block I have on the truck because of all the electrical crap I have added to it.

To make a long story short, if I have my heater/AC fan on high, and shut the truck off, the truck won't shut off. 12 volts feeds back through the relay to the junction block and from there some how to the 12 volts I have feeding the HEI.

So I don't have to figure it out, I just flip the fan off high the 1 in 100 times I turn the truck off and it won't shut off.

Now if I had a BRAND NEW "made to fit" harness, and it did this, I'd call and complain. If you need a diode to get around this issue, they should have a big fat note in the descructions stating that if you run an HEI instead of points you need to have a diode keeping current from back feeding into the ignition circuit.

[muddpile]

Wow are there a ton of things this could be it sounds like. Ok, I have an internal regulated alternator with HEI, and no diode, as painless didn't mention it. Sound like the problem?

With the truck off, the coil wire has no power. When the truck is on, but not running, the coil wire has power.

Battery cable is brand new, and nowhere near the exhaust

There is no electric fan, and no alternator light. All those wires are insulated and tied up.

[MUNYPIT70]

You need the diode. I had the same problem and called their tech line after about 3 weeks of fighting with it and that was what they told me. it took about five minutes and about 3 bucks. Now it works like a charm! THe thread above has the correct part number too, an it is the white wire. good luck!

[muddpile]

Thanks guys! I will be picking one of those up next time I'm near a "Source" (all the Radio Shack's up here are now called "Source"). So do I just ask for a diode #276-1661 and they'll know what I'm talking about? I sometimes have little faith in retail employees

[HD2000]

I picked mine up at "The Source" - didn't have to deal with the dumbfounded look from the employees as it was within easy reach back in the electronic parts section. If memory serves - a pack of 2 was around $5.

[Hardway]

I have a '72 with the same problem. I posted a thread with info from Painless in it. Check it out here: http://67-72chevytrucks.com/vboard/s...ht=backfeeding

[muddpile]

I picked up a pack of diodes, 4 of em for 4 bucks. So, where to I install these in the white wire? Near the alternator or where? Also, do I crimp them in, solder them, or what works best? Pictures would be great.

[Frizzle Fry]

Originally Posted by muddpile

I picked up a pack of diodes, 4 of em for 4 bucks. So, where to I install these in the white wire? Near the alternator or where? Also, do I crimp them in, solder them, or what works best? Pictures would be great.

Doesn't matter where you put it on the white wire, as long as you put the striped end of the diode toward the alt. It would be easiest to simply butt-splice or solder it in place right next to the alt plug, but you could put it elsewhere for aesthetics. I'd also put heat-shrink over the whole diode/splice.

[muddpile]

Thanks a lot! I'll put it in tonight.