Welcome to the Corvette Forums at the Corvette Action Center!

Help! 1995 Auto, No Crank, not VATS

Rob Dennis

Member
Joined
Sep 17, 2013
Messages
6
Location
Cape Coral, Florida
Corvette
1995 Polo Green Coupe, Auto; 1985 Black Coupe
All – I’m presenting the below as a bit of a story, because I want to give everyone as much insight into the issue as possible, the context around it, and what I’ve done. So, please bear with the verbosity of my tale! :O)

I have a 1995 coupe, automatic, which I’ve owned for several years and drive daily. No accidents and no major service. Recently, I’ve had electrical issues which I thought would be of interest to the forum (and, obviously, to me!). And yes, I know the sage electrical advice: “There’s smoke in them-there wires. If you lets the smoke out, they don’t work no more!”

What happened: The other night I drove the car to dinner with the wife. Normal drive, no issues. Roughly 30 minutes into dinner I heard the alarm going off (have to love those distinctive and decidedly un-manly Corvette horns). I’ve had issues with the door-ajar switches previously, so, reset the alarm, and went back to dinner. I hadn’t bothered to re-adjust either door’s switch, so I fully expected it to go off again. Surprisingly, we finished our dinner in peace. Even more surprising was the no start when we got back into the car!

No click from the solenoid and good headlights, so, at this point I’m thinking VATS is raising its annoying head again. But here is the thing: The security light wasn’t on when attempting to crank. And I noticed something else – the head unit for the climate control was not shutting off, period, keys out and in my lap. Oh jeez, VATS or some weird back-grounding/b+ short issue, great! So – long story short – it takes AAA approx. 1.5 hours to show up on a Saturday night. 1.5 hours is a long time in a Corvette with an irritated wife…

So, at home, with tools, FSM, and scanner in hand, determined the following:
No start was where I would start. In this case, no click from the starter solenoid, so followed the appropriate trouble shooting steps in the FSM and eliminated the following as potential sources of the issue: Battery and connections good, starter & solenoid is good, park/neutral safety switch is good (and properly adjusted), ignition switch is good, got to anti-theft (or starter) relay.

At this point I jumped the anti-theft relay across the secondary (large ~10 gage purple and yellow) wires and the car cranked right up, ran just fine, all working and no MIL. OK, so why isn’t this relay closing on its own? Is it bad? Swapped it with the DAB relay right next to it (which was on and working just fine; listening to the radio). Swaped ‘em back and forth, both relays worked on DAB circuit, and nether worked on Anti-Theft. OK, relay is good.

Back probed the primary power to the relay (~16 gauge brown wire) from the ignition switch, and it’s getting power. Well, shoot, then all that’s left is the primary ground from the CCM (~16 gauge yellow/black wire), and guess what? No ground from CCM! And at this point the FSM says to “service the CCM“. Oh, great – I really don’t want believe you, FSM.

Bah! Back to double check the <edit, edit, edit> VATS. Interrogated the CCM, had no fault codes. Disconnected the VATS wire to the ignition lock cylinder and re-tested. As expected, immediately got [C53 Pass-key – key detection circuit open or shorted to battery]. Re-connected, re-tested, no faults. So now I’m convinced VATS is working as intended for two reasons. 1) the C53 test I just performed and 2) the fact that it will crank and RUN if I jumper the anti-theft relay. I think if VATS was really malfunctioning, I’d have no crank AND no fuel pressure (VATS disables fuel as well).

So – the other thing I mentioned at the top of the story is that the head unit for the climate controls (AC controls) will NOT power down with the ignition off and keys out. As a side note I have RPO C68 – Automatic electronic air conditioning. So, since it won’t power down without disconnecting the battery, I’m thinking I have a grounding issue and it’s back feeding through the AC in seeking ground? And to back that suspicion up, it looks like the CCM does all of its magic by switching to ground – which wouldn’t work very well if the CCM isn’t grounded, or is only partially grounded?

So – My questions:

Before I go digging for errant ground wires, do you all agree with my suspicions? Has anyone else run into something like this, or have pointers on what else I should check for first?

I just love the block car diagram in the FSM showing where the chassis grounding points are located. Not real helpful, IMHO. Anyone have advice or pix showing where those chassis grounds really are? Or suggestions for which one(s) I should check first?

I was thinking to run temporary “jumper” ground wires to the two ground circuits feeding the CCM (CCM connector positions C1 & E16; the inbound grounds, not the switched outbound grounds). This would just be to see if this clears the no-start, an attempt to confirm the CCM is working properly.

Even if it works, it’s not a permanent solution. The AC being stuck on drains the battery in ~60 minutes. Of course, grounding the CCM might also ground and shut off the AC… :O)

Thanks in advance for everyone’s help.
 
Last edited:

ecss

Well-known member
Joined
Nov 27, 2004
Messages
649
Location
Windsor Mill, MD
Corvette
89 Brilliant Red Metallic
The only thing I see common between the C68 control head and the CCM is both
the AC Clutch fuse and CCM3 Fuse#16 both get 12 volts from the same ignition switch
contact when the ignition switch is in Run.

Orange wire on Connector C1 pin A at the ignition switch.

For the C68 control head 12 vclts comes from Fuse #18 AC Clutch fuse.

The CCM gets power from 3 sources called the following.
Fuse #35 CCM1 (Ignition Run or Start)
Fuse #39 CCM2 (Battery Input)
Fuse #16 CCM3 (Wake up "Run")

Both fuses are located in the fuse panel passenger side end of dash.

If you use a volt meter with the ignition OFF there should be no voltage on
Fuse 18 AC Clutch fuse or Fuse #16 CCM3.

If you pull Fuse #18 AC Clutch fuse, the Control Head should shut off.

If there is voltage at either fuse with the ignition OFF, something is wrong with
the ignition switch or some how the Orange wire is getting 12 volts from
some where.
 
Last edited:

Rob Dennis

Member
Joined
Sep 17, 2013
Messages
6
Location
Cape Coral, Florida
Corvette
1995 Polo Green Coupe, Auto; 1985 Black Coupe
Update

Last night I dug into the radio. It's the only non-stock electrical component on the car, and it sits right there in front of the CCM and all that associated wiring. I'd done the radio install myself about a year ago, using a plug-in wiring harness from Metra (a very good product, by the way).

Anyhow, when I did that install, I was careful to solder and shrink-wrap all the connections. Also, I wrapped it all in black corrugated wire loom to both protect it from abrasion and give it a factory appearance. Long story short, there were no issues with the radio install or wiring. And sitting there looking at the CCM buried way down in there was a bit depressing.

So - I decided to quit for the night. I was sick of disconnecting the battery, so I started pulling fuses to get everything to shut down (and, in the back of my mind, to see where my amperage draw might be coming from).

As ecss suggested, pulling fuse #18 did shut down the AC controls. But I still had a pretty big amperage draw (I should mention that I’d already pulled all the interior lighting fuses at this point). Anyhow, I just started going fuse by fuse, looking for a big drop. Fuse #17 Valet was the winner, huge drop. OK. Put fuse #18 back in with #17 out. No increase to amp draw and the AC IS STILL OFF! Hmmmm.

I went back to the driver side, plugged back in the anti-theft relay, crossed my fingers, and fired that sucker right up! OK. So the CCM is fine (whew), VATS is fine, AC is fine. All is fine if I just remove fuse #17 Valet. Then I back probed fuse #17. B+ on both sides?! That's not right! So, I began testing it.

On the incoming power side (from the ignition switch) it is supposed to be switched. Meaning ~12V when the key is in run, 0V when key is in any other position. This tested out just fine. On the other side, which is the outgoing fused harness, there should be no voltage when the fuse is out. Well, I have ~12V hot there at all times.

Ecss – your advice was spot on and would have lead me right to the heart of the real issue.

So – I have a short to B+ on circuit 641. When fuse #17 is inserted into this circuit, it feeds constant power to that entire row in the fuse box (the fourth from the top, or fuses 16, 17, 18, 19, & 20). Since #16 is power to the CCM when the key is in the “run” position, I assume the reason CCM prevented me from engaging the starter was because it thought the car was already running! Smart.

So, what does old #17 feed? Well, on VIN P, not much. Never imagined I’d say this, but thank goodness I’m not driving a VIN J, where #17 Valet feeds a whole lot more. :O)

Anyhow, #17 fuses the B+ signal to the voltage regulator in the alternator, and provides power to all the solenoids in the transmission. Could all this just be a short inside the alternator?!? So I ran around and unplugged the pigtail to the voltage regulator on the alternator. No dice, still shorted to B+. Sigh.

And at this point it was after midnight and I really needed to go to bed. A few years ago I’d replaced the voltage regulator pigtail (the original connector was brittle and just fell apart). I used a new connector (I think from Dorman) and the same solder, shrink-wrap process back then, and externally it all looks fine. But that signal wire runs (in the harness) right along the main B+ feed from the Alternator back to the battery. Sure would be an easy source to pick up a short to B+…

So, I’ll tear into that tonight and let you all know what I find. Cross your fingers for me and thanks again ecss for your excellent advice.
 
Last edited:

Rob Dennis

Member
Joined
Sep 17, 2013
Messages
6
Location
Cape Coral, Florida
Corvette
1995 Polo Green Coupe, Auto; 1985 Black Coupe
Fixed!

Alright - It was a B+ short to the feed wire from the alternator, as suspected. Here are a few pics of the repair.

PICT2698.jpg
Here you can see the red shrink tape has partially melted and begun to harden and chip away.
PICT2699.jpg
Here all the red shrink tape has been removed, showing the original repair and black heat shrink wrap.
PICT2700.jpg
I could not find any obvious breaks in the insulation and the structure of the wire seemed sound.
So, I made the potentially risky decision to attempt repair the insulation (instead of cutting out the old wires and splicing in new). I may pay for this later, we'll see.
I did two things for the repair, first I used this stuff, which goes on very thick to act as a moisture barrier.
PICT2701.jpg
Then I taped each individual wire with electrical tape, then all the smaller wires into one bundle. Note I left the large alternator feed wire by itself.
PICT2704.jpg
Here is the finished repair. The white zip ties are a bit ugly, I didn't have any more of the red friction/shrink tape.
Later I'll get some more tape (in black this time) and wrap the ends of the corrugated tubing like the factory does.
To the lay person they will never notice the fix.
 

ecss

Well-known member
Joined
Nov 27, 2004
Messages
649
Location
Windsor Mill, MD
Corvette
89 Brilliant Red Metallic
Since you found no sign of where the Brown wire that provides 12 volts for the Alternator
regulator was contacting either Red wire, my guess is the solder joint at the Brown wire
when bundled up pierced thru the heat shrink tube into either the Red wire for the Alternator
Battery terminal or the Red sense wire.

Both Red wires are fusible liinks and trerminate at the same place, a bolt at Underhood Fuse Block#1
located behind the battery near the A pillar. From that point they both get 12 volts from the Positive
battery terminal.

Here's a picture of Fuselink A a Fuselink B.

I've noticed due to the high under hood temps. you have to use high quality products
that can take the high under hood temps.

 
Last edited:

Rob Dennis

Member
Joined
Sep 17, 2013
Messages
6
Location
Cape Coral, Florida
Corvette
1995 Polo Green Coupe, Auto; 1985 Black Coupe
Followup

ecss -

Yes - I thought the same regarding the solder piercing through the shrink wrap and looked for that. I didn't see it or feel it - but it had to be there, you know? Grrr.

Not sure you can tell from the pix, but I don't use the metal crimp & solder method. Rather I gently fan out the individual wire strands on each wire, push them together so they interlace, twist into an elongated oval shape, dab of flux, solder. Kind of like lacing your fingers together. If done properly, the twisted halves end up being roughly the same diameter as the old wire & insulation, and the wire ends fold smoothly together with no stray wires pointing out. If any strays do poke out - and then you compound the issue by making them stiff with solder - they can easily pierce the shrink wrap.

And your other point is not lost on me. I used the cheap shrink wrap from Home Depot, and your right, I feel certain it's not rated for either the temps or for an oil environment. I had reservations last night when I did the repair, but it was drizzling, light was failing, and this got the car back on the road. But it's bugging me the more I think about it, and what I just typed seems like a lot of lame excuses. :O)

So, I'll order another pigtail and re-do it properly on a weekend, in the daytime, when it's not raining. I think Grainger has the good shrink wrap, do you know of another (or better) source? I can go to the old inter-web, but it would be nice to buy local if I can...

While I'm at it, I'll get more of the black shrink/friction tape to properly finish the joints and ends of the plastic corrugated loom. You know, lose the "zip-tie-Frankenstein" look. Thanks again for your replies, sage advice, and also the illustration.
 

Rob Dennis

Member
Joined
Sep 17, 2013
Messages
6
Location
Cape Coral, Florida
Corvette
1995 Polo Green Coupe, Auto; 1985 Black Coupe
Solder Technique

Found this image on the internet, it shows the technique. However, if you look very closely at this image, you'll note a stray wire end on the bottom right that might pierce the shrink warp. It's small, probably not, but it could easily be covered with another dab of solder.

Thought I'd share. I've seen so many folks who just twist the wires together like they were going to screw on a wire nut.

untitled.jpg
 

Corvette Forums

Not a member of the Corvette Action Center?  Join now!  It's free!

Help support the Corvette Action Center!

Win Both Corvettes!

Win Both Corvettes and Get Extra Bonus Tickets Now!

Supporting Vendors

Dealers:

MacMulkin Chevrolet - The Second Largest Corvette Dealer in the Country!

Parts/Accessories:

Dead Center Foundation

Vetteskins

Advertise with the Corvette Action Center!

Partners

Top Bottom