68 electrical gremlin chasing

C3 Specific - Technical and Performance

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68ragtop
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68 electrical gremlin chasing

Postby 68ragtop » Mon Jun 15, 2015 9:02 pm

Isn't it great how Corvettes always find a new way to give you a little bit more to work on just as you think things are getting sorted? My fun this time turns out to be an electrical gremlin lurking somewhere. Symptoms go a little something like this:
  • Turn the key and seat belt waring light/stereo comes on, turn it again to start it and hear a loud click like the solenoid trying to engage the starter but then nothing. No power to anything.
  • Turn everything off and then try again, car starts. Move it outside the garage and it stalls (too cold and not warmed up yet) while I close the garage door. Try to start it again and same result as the first point.
  • Do the off and on thing again but no power at all. No lights, accessories, nothing. Push car back into garage. :cry:
  • Try again a few hours later and still nothing
Now it's done this once before a few years back but I just thought at the time it was the masses of oil covering the solenoid as after a good working over with degreaser all came good when I turned the key the next time. No leaking oil any more so there's that theory blown.
So at this point I check a few things:
  • Battery is nicely charged
  • Ground lead at battery is good. Clean up the contact between it and the frame just in case.
  • Hot strap from battery to starter solenoid looks good and has 12v on it
  • Hot lead from starter to Alt has 12v on it
  • Hot lead from starter to power dist block on firewall has 12v on it. No worry about fusible link as find it's been replaced with a normal wire lead instead!
  • Dropped out and bypassed the starter and eliminated the alt just in case they were causing issues. Still no power run anything in the car, not even lights, but still 12v at the dist block

And then it just got weird as I checked things again after disconnecting the battery via the quick disconnect on the earth lead. Checked at the power distribution block and multimeter showed it still had 5v on it but was dropping off slowly. :shock: This is with the starter and alt completely disconnected. All I can think of is that something under the dash has turned into a capacitor and is taking/grounding the charge from the battery before it can power anything. Next steps are working through the hot power dist junction connections(below) to see where the mystery voltage is coming from, checking the fuse box, and eliminating things like the ammeter and stereo as the culprits. At this point any other suggestions are welcome.
Image

Other thing is I found in taking off the bolt on the solenoid that the copper thread is toast, probably done by me last time I contorted myself to get the bolt back on. Think I'll be seeing if I can find a cheap second hand unit at a wreckers or online to replace or rebuild this.
Image

Add to that finding the power steering pump seemingly leaking from the pulley shaft and the weekend was awesome. :evil:

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Wabco40
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Re: 68 electrical gremlin chasing

Postby Wabco40 » Tue Jun 16, 2015 6:00 am

I had a similar problem with a 71, turned out to be a faulty battery/amp gauge.

Try unplugging the gauge and bridging out the plug.

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Re: 68 electrical gremlin chasing

Postby Trudgeo » Tue Jun 16, 2015 8:23 am

WOW Azza, i had a similar problem with the '77 that i built...........try undoing the power block to the fusebox from the firewall side and make sure ALL the contacts are clean and dry, reassemble with CRC or WD40! yes, also check you amp meter as Wabco suggested! :o :)

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Re: 68 electrical gremlin chasing

Postby sirfixalot » Tue Jun 16, 2015 8:38 am

The amp meter path is only a shunt in parrallel with wire which feeds every circuit in car. The side mount battery terminals can go open circuit internally if the bolts are over tightened.There is no indication on outside of battery. The only indication is the symptoms that you have that the car intermittently wont start.

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68ragtop
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Re: 68 electrical gremlin chasing

Postby 68ragtop » Tue Jun 16, 2015 12:18 pm

sirfixalot wrote:The side mount battery terminals can go open circuit internally if the bolts are over tightened

Finally something the unique 68 parts bin of a car got right.... original 68's came with top post batteries. :)
And battery is good enough to spin the starter while bench testing it.

Back to tracing the circuits this weekend against the wiring diagram I have. Maybe first stop will be checking something I found a while back...if stereos main power feed (e.g. wire with a spade connector that is jammed in next to a fuse) has come loose :-)

Trudgeo wrote:Hope you sort out your gremlins soon Azza, remember I might be able to help you with the starter motor :shock:

Cheers George, you were gonna be my first call to see if you had a spare, but through a guy at work I may have a line on a new cheapish gear reduction mini starter to get me a tiny weight saving as well as a starter that may be less susceptible to heat soak.

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DOC
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Re: 68 electrical gremlin chasing

Postby DOC » Tue Jun 16, 2015 5:31 pm

I'd be checking with a load tester. Pull a load at the alt. lead etc.

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Re: 68 electrical gremlin chasing

Postby 68ragtop » Tue Jun 23, 2015 12:06 pm

DOC wrote:I'd be checking with a load tester. Pull a load at the alt. lead etc.


That was a good idea. Used some jumper leads, a wired up extra switch and the starter solenoid to test pulling a good load across the leads form the battery onwards. Found ground lead was good. Found the connection from the battery to the starter wouldn't carry any load. Went to take the connection off the battery and the clamp broke apart (was an old lead one) so even though it looked good and felt tight it was about to let go. Got a new clamp and put it on and went to reconnect the negative quick disconnect to test things and the bloody thing snapped off on me too. So much for the "green button" type disconnect from SuperCr@p Auto and the cheap coated metal it's made from. Outlasted by the battery itself!

So will be finding a newer slightly more heavy duty disconnect somewhere this weekend as well as fitting a nice shiny new starter. Then on to checking if it was just the positive connection or if it's the actual positive lead that's dodgy. Then maybe I might get to give her a run for the first time in a month.

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Re: 68 electrical gremlin chasing

Postby Bazzas77 » Tue Jun 23, 2015 12:23 pm

68ragtop wrote:


So much for the "green button" type disconnect from SuperCr@p Auto and the cheap coated metal it's made from. Outlasted by the battery itself!
[/quote]

I had one of those , it snapped while I was at the shops so I drove home with one hand on the steering wheel and the other holding both parts together :-x :-x

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Re: 68 electrical gremlin chasing

Postby Ollie68 » Thu Jun 25, 2015 9:46 pm

Bazzas77 wrote:
68ragtop wrote:


So much for the "green button" type disconnect from SuperCr@p Auto and the cheap coated metal it's made from. Outlasted by the battery itself!


I had one of those , it snapped while I was at the shops so I drove home with one hand on the steering wheel and the other holding both parts together :-x :-x[/quote]

:shock: That's no easy task, well done :o
:D
Ollie

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Re: 68 electrical gremlin chasing

Postby Bazzas77 » Fri Jun 26, 2015 8:59 am

didn't have much choice :-o but being rhd its easy to reach over to the battery ::

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68ragtop
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Re: 68 electrical gremlin chasing

Postby 68ragtop » Sat Jun 27, 2015 12:42 pm

Picked up new starter and went to fit it and needed bolts 5/8" shorter! Went out and picked some up as well as a battery isolator switch. Bolted it in and went to connect the wiring and found the ring connector on the wite from the ignition was too small and I'm all out of a size that will fit so off out again for more parts. One day I'll get this thing in!

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DOC
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Re: 68 electrical gremlin chasing

Postby DOC » Sat Jun 27, 2015 2:45 pm

What a Battle!

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Re: 68 electrical gremlin chasing

Postby 68ragtop » Sat Jun 27, 2015 6:53 pm

And she lives!!! New connector on, new starter bolted in (with some spare 4" high tensile bolts which should do for the moment), both battery clamps replaced after they had both snapped and she fired up first time. New starter sounds a bit like a little turbine winding up but worked great with no issues with clearances to the flywheel. Sure no ones gonna see it but the chrome looks nice to me and the thing is smaller and half the weight of the original even if the back brace no longer fits. :) Time will tell if it causes more heat to be retained in the starter causing issues after long hot runs.

Image

So took her out for a test drive down to the waterfront and she was running nicely, but the ammeter was showing a slight drain rather than a charge. Checked it out when I pulled over and had a Doh! moment when I found I'd forgotten to connect up the alternator after testing the wiring there! Fixed that up and now she's charging like a champion again.

Onwards to the next things found while doing this... slow radiator drip from the drain plug, and 4" of stitching letting go around the side of the soft tops window. Then there's those pesky trailing arm rebuilds to schedule in. But at least right now I can drive it again -)

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Re: 68 electrical gremlin chasing

Postby DOC » Sun Jun 28, 2015 10:37 am

Sounds good Aaron. With half the weight the back brace shouldn't be an issue,
Try putting some heat reflective material over the starter. Works a treat to keep the starter from heat soaking.

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68ragtop
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Re: 68 electrical gremlin chasing

Postby 68ragtop » Sun Jun 28, 2015 12:12 pm

More reflective than chrome? :-x I do have some fibreglass wrap with an aluminium outer that i used to wrap the old starter but this one i think i'll just leave to see how it does first. Seemed fine after a run to redcliffe ans back. As for the brace my original starter didn't have it (or the ground strap from the frame connected) until 2 months ago so I'm not too worried.

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68ragtop
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Re: 68 electrical gremlin chasing

Postby 68ragtop » Wed Jul 01, 2015 10:00 pm

Well starter works like a champion even when hot after 1hr 40 on motorway doing 10 kph in stop stop start stop traffic! Clutch was a little loose by the end though. But sounds like there is a new whine down by the new starter so am now wondering if it's disengaging properly.

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Re: 68 electrical gremlin chasing

Postby riverracer » Wed Jul 01, 2015 10:24 pm

when i had to replace my starter last year due to poor workmanship on it's rebuild, i just got another full size unit off local ebay.

i don't have a rear brace on my full size starter, but have been thinking about putting one on, as they are a heavy sucker,

wanna sell yours? :-o :)
Speed has never killed anyone,
Suddenly becoming stationary that's what gets you.

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68ragtop
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Re: 68 electrical gremlin chasing

Postby 68ragtop » Thu Jul 02, 2015 7:35 am

River it's yours if you want it as it's no use to me any more.


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