The 1947 - Present Chevrolet & GMC Truck Message Board Network - Rewired 70 C10 heater and running lights on even if ign is not plugged in.

The 1947 - Present Chevrolet & GMC Truck Message Board Network (https://67-72chevytrucks.com/vboard/index.php)

- The 1967 - 1972 Chevrolet & GMC Pickups Message Board (https://67-72chevytrucks.com/vboard/forumdisplay.php?f=3)

- - Rewired 70 C10 heater and running lights on even if ign is not plugged in. (https://67-72chevytrucks.com/vboard/showthread.php?t=742108)

Re: Rewired 70 C10 heater and running lights on even if ign is not plugged in.

Well you're still at it huh. Here is what I would do.
Disconnect the steering column wiring harness and put a new fuse in the stop turn holder in the fuse panel.
get a jumper wire about six inches long.
Turn the key on so you have power on the purple wire.
Jump between each of the turn signal wires both front and back and the purple wire.
See which one blows the fuse and that will tell you which one is shorted to ground.
If all the bulbs light and the fuse doesn't blow, then the short is in the turn signal harness or the switch itself.

Re: Rewired 70 C10 heater and running lights on even if ign is not plugged in.

What about the third option? The option where I do jump the purple wire to each individual and ALL of them pop the fuse?

From one of the posts above: With the switch disconnected and the battery connected, jump the purple wire and the yellow and light blue (2nd test was purple jumpered to DG and DB) and turn the key on. The left/right marker and indicator lights should blink.
Nope. The Turn signal fuse popped both times I tried this.

I have also tried unplugging the front marker/turn lights (fuse blows) and disconnected the rear turn lights (fuse blows).

Now, I am willing to try jumping the purple wire jumped to each individual one but at this point I am betting that they will all blow the fuse. I will also need to buy yet another box of 10 amp fuses so that I can make sure I have at least 4 to try.

Re: Rewired 70 C10 heater and running lights on even if ign is not plugged in.

..................

Quote:

Originally Posted by C10Coloradoguy (Post 8027816)

I have checked the switch as requested and just so you know, yes the colors all match on my harness so everything you say makes sense. If I don't quote something from your instructions it means that it worked. I did have some variations though. Here are the results:

Red meter lead on purple wire and black lead on dark green with switch in neutral. Supposed to be no ohms. --- I am using the 20k setting on ohms and coming up 0.85 ohms. Not sure if this is close enough to zero or if it is an issue.

You should be using the lowest scale that you get a reading on. Are you using an analog meter with a needle or a digital meter? You should be seeing enough resistance that the bulb won't light. I would expect no reading. Then when you move the switch lever to right turn you should get continuity or very low ohms.

Red lead on purple, black lead on yellow with switch in neutral. Supposed to be no reading -- I am getting 0.84 or 0.85 ohms.

Same thing here on left turn.

Red lead on brown, TS in neutral, hazard out. Touch black lead to the four turn wires. Supposed to be no reading. -- I am getting .04 ohms on each wire.

Does your hazard switch turn on the lights when pulled or pushed in? If when pulled you should get continuity on all four wires, Low ohms on lowest scale. They should have continuity to each other as well because the switch connects all of them to the brown hazard wire.

Just for kicks: Red lead to yellow wire and black lead to the other three wires (DB, LB, DG). This was done bypassing the switch and tested where the harness connects to the TS coupling LB and DB had no reading, but DG shows continuity (0 ohms). I believe this is a problem.

If both wires Y and DG, were shorted to ground and You checked between them for continuity you would get zero ohms, so yeah this is a problem.

I have traced back the yellow and green wires from the harness back to where they split right and left and I can see no place these wires are touching each other. How else could they show 0 ohms?

see previous.

Did you check the harness from the front and slong the frame rail for a clamp pinching or grounding the two wires?

Side note: I had printed out some test instruction that I could have sworn were from VV but looking back on this thread it must be another 68 -72 C10 forum post. Here are the two tests I ran and the results were the same:

With the switch disconnected and the battery connected, jump the purple wire and the yellow and light blue (2nd test was purple jumpered to DG and DB) and turn the key on. The left/right marker and indicator lights should blink.
Nope. The Turn signal fuse popped both times I tried this.

Incidentally, all of the tests I ran on the TS switch for left and right turn seem to work according to the multi-meter. I don't think it's the switch. Something more difficult....of course. :waah:

Re: Rewired 70 C10 heater and running lights on even if ign is not plugged in.

If you had the grounding in the above and you had the ground in the indicator bulbs in the dash, it would explain all your symptoms including the hazard blowing fuses.

I suggested you pull the dash plug in a previous post and checking for grounded wires in the front turns. You need to isolate each light to find out which one is grounded.

Re: Rewired 70 C10 heater and running lights on even if ign is not plugged in.

More puzzle pieces

Sorry Moose, not yet, I was sick for a week and just started playing with it again.

I bought an $8 test light and another box of fuses so I can move forward. I hooked up the battery and then clipped the test light to ground and tested the red wire on the back of the fuse block that is the input for both the purple and the brown wire that run to the TS switch. (The purple TS switch feed and the brown hazard feed wire share this red wire on the fuses with the TS switch to the left (10 amp) and the hazard to the right (15 amp))

Light comes on so this red wire is good.

Touched to the backside of the fuse block on the hazard (brown) wire. Light came on so this wire is good.

Touch to the purple wire....nothing. I've suspected this wire from the very beginning but I can't see anything wrong with it. Delving a little further I used my digital multimeter to test further, after unhooking the battery of course.

On the AAW harness, on the back side of both the TURN and the HAZARD fuses, there is the red wire input on one side and then each side runs a short jumper wire to one corner of the fuse block where the flashers connect. It is here where both main wires run directly from the fuse block and up to the TS switch. So the question begged, is it a problem before or after the flasher?

Back to the multi-meter: So, checking for a clear path to ground, I set it to 20k on the ohms scale, put the black lead to a good ground, and then put the red lead to each wire. Red wire: 0 ohms, no resistance. Brown wire: 0 ohms, no resistance. Purple wire: .85 ohms, resistance. Hmmmm This tells me it's the jumper wire and not the main purple wire.

That's how far I am right now. Still trying to understand why there is resistance in the wire and what the solution is.

Re: Rewired 70 C10 heater and running lights on even if ign is not plugged in.

Keep going you are getting closer. Glad you are feeling better.

Alright, I just had a revelation that hopefully will lead me to the issue. My inexperience and bad eyesight led me to believe that the HAZARD and the TURN fuse shared a power source (12v red wire). Doing some more digging and unhooking with the purple jumper wire led me to realize that only the HAZARD is fed by 12V red wire. The left side of the TURN fuse is actually open but it runs on a line that has 2 Pink Ignition Feed wires.

One P.I.F. wire runs directly to the ignition terminal of the ignition switch and the other runs to the ignition side of the distributor (HEI in this case). They look to be hooked up correctly according to the AAW instructions and independent sources. So now I'll start testing those wires and see what I come up with.

Front park/turn lights are the problem

I got ahold of AAW and we ran a couple of tests. We were able to bypass the switch and found the rear turn signals work fine. Then we tried both front turn signals. The front park/turn lights are grounding when the switch is flipped and causing the fuse to blow. I'm certain this is what is causing the issue.

Waaaay back in this thread there was a time when I switched the wires on the front park/turn lights and this allowed the park lights to work. But on my harness the connectors for the front park/turn lights that plug in at the radiator support are [B]3 wire[B] and not two wire like every schematic that exists for this model truck. AAW even said this was unusual and is probably some kind of aftermarket connector.

I'll note here that the guy I bought this truck from was basically a used car salesman and lied to me about several things and said the electrical worked just before I drove it home with headlights only. So once again, I'll curse his name: THAT F*****G GUY!!! (where is the emoji with two middle fingers? You can name it after me.)

So with a 3 wire connector, one should go to park, one should go to turn, and one should go to ground (presumably). Since the park lights work I took the two remaining wires on each side (ground and turn) and switched them. Then hooked up the battery, turned the ignition, and tried the turn signal again. And the fuse popped....again.

As I said above, every schematic I've seen has two wires into the front park/turn lights and is grounded at the bulb. I believe this connector is incorrect so I am going to cap off the ground wire on each connector to see if that solves it. If not, then I'll have to look for different connectors. We'll see what happens. :chevy:

Sure enough, that extra wire on both sides of the park/turn lights was the problem. I capped off both sides so that there was just input to both sides of each bulb and now everything flashes and lights up as it should. Thanks to everyone who contributed to this thread. It's been an arduous journey but I have learned a ton along the way.

Keep em' on the road! :metal: