89 K3500 Firewall & A-pillar holes question

Question for the experts... I'm looking at two very factory looking punched holes. One in the firewall directly to the right of the cruise harness hole and one on the drivers A-pillar. The A-pillar hole had a plastic block-off plug I believe. Truck had manual windows so the A-pillar hole is a mystery but obviously the plug means it was a mistake or just not used for anything. The firewall hole is the big question, what was it used for? 1989 K3500 reg cab dually L19 M40 C60

A mistake? As these a produced on large stamping machine , producing hundreds , thousands, that is probably a not likely .
But a good way to spread bad information.

The A-pillar (door jamb) hole is for power windows/locks wiring; just because the truck came without doesn't mean they don't go ahead and punch the hole. The plastic plug is there from factory. I've had a few trucks like this.

The firewall holes, dunno, drawing a blank at the moment. Haven't seen factory holes in those spots. Probably somebody added equipment and actually used correct tools to make the holes for wiring/hose access instead of hacking it.

Richard

someotherguy said:

The A-pillar (door jamb) hole is for power windows/locks wiring; just because the truck came without doesn't mean they don't go ahead and punch the hole. The plastic plug is there from factory. I've had a few trucks like this.

The firewall holes, dunno, drawing a blank at the moment. Haven't seen factory holes in those spots. Probably somebody added equipment and actually used correct tools to make the holes for wiring/hose access instead of hacking it.

Richard

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Thanks for the reply. There is only one firewall hole in question. It was coated in the original paint so it's unlikely someone cut it after the fact. Every pickup I've checked in the junkyards does not have this hole.

tookool said:

Thanks for the reply. There is only one firewall hole in question. It was coated in the original paint so it's unlikely someone cut it after the fact. Every pickup I've checked in the junkyards does not have this hole.

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Neither of those firewall holes appear original, unless I'm forgetting some piece of original equipment from that era.

Here's a '94 3500HD firewall.. notice no holes above the square one for the wiring harness connection. The round hole to the side with the diagonal bolt pattern is for the clutch master.



Richard

GoToGuy said:

A mistake? As these a produced on large stamping machine , producing hundreds , thousands, that is probably a not likely .
But a good way to spread bad information.

Click to expand...

Did you ever work in an automotive assembly plant? I did and mistakes did happen.

someotherguy said:

Neither of those firewall holes appear original, unless I'm forgetting some piece of original equipment from that era.

Here's a '94 3500HD firewall.. notice no holes above the square one for the wiring harness connection. The round hole to the side with the diagonal bolt pattern is for the clutch master.

You must be registered for see images attach

Richard

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On my firewall, the larger of the two holes near the wiring harness bulkhead square hole is used for the cruise control harness. It's probably more common an option on a pickup than a 3500HD

tookool said:

On my firewall, the larger of the two holes near the wiring harness bulkhead square hole is used for the cruise control harness. It's probably more common an option on a pickup than a 3500HD

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There you go.. absolutely, that HD did not have OEM cruise on it. (I do believe I recall removing some weird aftermarket device; the truck was formerly a 6.5td as well) - and I wouldn't have remembered drilling that hole in the '94 when I engine-swapped it as I went with a Vortec 7.4 out of a '96, including all the associated wiring, interior change, etc. and they didn't utilize that hole for the cruise. They added an angled section to the square hole for the wiring block, so I had to cut that part out a bit.


I've got some misc. other pictures I've looked at from projects over the years and there is one original hole above the square one for the wiring block on the TBI-era trucks, does in fact appear to be for the cruise harness.. so I stand corrected on that! Maybe the smaller hole next to it was one someone added to run power wiring for an aftermarket stereo, or whatever work-truck type accessories it may have had in the past.

Richard