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Firewall Wiring - Tick-Tock Tach + Cruise Control???

PurpleBeeper

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1970 Roadrunner
For cruise control, where does the wiring pass through the firewall? In the one picture I've seen, it "looks" like it's going through the hole where the single gray wire is for the tick-tock tachometer (original on my car). I'm trying to retrofit cruise control.

So, does anybody have a tick-tock tachometer GTX or R/T or something that also has cruise control? Anyone have a picture where the cruise control wiring goes through the firewall?

THANK YOU!
 
Most factory and dealer Cruise Control installations from that time routed related wiring though the firewall outboard of the master cylinder. Angled hole in place for pluming of a foot pump windshield washer, normally plugged off. The harness has a 1” molded grommet for this purpose.


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On 3rd gens the cruise control harness goes close to acelerator pedal ( I have the pic somewhere around ). The outboard provision is actually for vacuum controls hose and heater valve wire.

Can't tell on earliers.

And it seems per I have noticed, tach wire on 71s and 74s used the free cavities on bulkhead, 72/73 are on a firewall with a grommet like earliers
 
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Vacuum hoses? for 3rd gen Charger concealed headlamps on a ’70 Road Runner? Actually, that 1” hole, outboard of the brake booster, dates back quite always on the b-body platform, originally to accommodate the foot pump washer system hoses. Most vehicles, without concealed headlamps, by ’70 ran electric washer pumps with this hole plugged off. Installed many factory CC retrofits kits at the dealer back in the day, the molded grommet is designed to use that hole.

What’s a “heater valve wire”?
 
On my car the manifold vacuum controls the A/C box actuators. It gets also a check valve to presservs the vacuum on actuators just right before the A/C car control.

The heater valve on engine bay is wire controled

Both leaves throught that grommet. In fact the grommet is molded to these accesory lines. I replaced the vacuum one and it was somehow glued. Just pulling it our it came out and run a the new line. Will be the same when I replace the heater control wire.
 
Most factory and dealer Cruise Control installations from that time routed related wiring though the firewall outboard of the master cylinder. Angled hole in place for pluming of a foot pump windshield washer, normally plugged off. The harness has a 1” molded grommet for this purpose.


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You have been INCREDIBLY helpful...thank you. What year is the car in your picture with the 6-pack? I will take a look at my '70 and see if I have that plug outboard of the master cylinder.
 
On 3rd gens the cruise control harness goes close to acelerator pedal ( I have the pic somewhere around ). The outboard provision is actually for vacuum controls hose and heater valve wire.

Can't tell on earliers.

And it seems per I have noticed, tach wire on 71s and 74s used the free cavities on bulkhead, 72/73 are on a firewall with a grommet like earliers
Hey Nacho, thank you too. What do you mean, "free cavities"? I have a non-A/C car & there is no vacuum on the 70 cruise control brake switch (just wires). However, I did notice 3 "dimples" on my firewall, sort of above the bulkhead disconnect area, that are for "something" that my car didn't come with.
 
The picture above on this thread is a ’72 and for reference only, this hole is present on some previous years and other platforms of that time.

That said, looking again at my 40-year pictures of my ’70 RR, the cruise control grommet appears to be between the bulkhead connector and booster. Would have drilled the hole for the installation at an existing dimple.
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68 Charger RT with tach and cruise. Tach wire goes thru above the bulkhead. I would have to look at the cruise wiring. The grommet posted earlier looks a lot like the one in my pic below the vacuum hoses. The tach wire is in a different location on the non-cruise cars.

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Wow...this is super useful information. Here is a picture of my firewall for a 70 Roadrunner, factory tic-tock tach, non-cruise.

My firewall 1 Compressed.jpg
Dang it, I can't get the picture turned the correct way. Anyhow, you can see the gray tach wire & 3 unused dimples above the bulkhead disconnect. It looks like the cruise/tach RT uses the right dimple for the tach & its cruise wire goes where my non-cruise tach wire is.

Also for reference, my car is an original 4-speed, non-A/C car too... I don't believe 4spd cars ever had cruise available stock

So what I'm seeing on PP1RT's car is his cruise wire & grommet look the same as where my tach grommet comes through the firewall. My non-A/C firewall doesn't even have a dimple where his A/C vacuum hoses come through. His tach has a slightly different (flatter) grommet and comes through one of the dimples not used on my car, I think the far right unused dimple. I may just use that hole for my cruise unless I can route it through the non-stock hole I already have drilled.
 
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My vacuum hoses would be for the hidden headlights (Charger). You have a dimple there in your pic. I dont know if much changed from 68 to 70 but you could drill the dimple above the bulkhead and run your tach wire. Put your cruise wires where your tach wire is now. That should put the cruise wiring where you need it (brake pedal).
 
Easier to see upright. Tach wire at upper arrow. Cruise wires at lower arrow.

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Dimple where my vacuum hoses come thru

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Easier to see upright. Tach wire at upper arrow. Cruise wires at lower arrow.

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Oh crap, you're right. So on my non-cruise, tick-tock-tach car, my tach wire goes where your cruise wire goes....and your tach is through one of my un-used dimples. I wonder why Mopar didn't just use the same hole for all tach wires??? Why didn't they just run your factory cruise wire through what is your tach hole & keep your tach wire in the same place as mine???

Is your car original tach/cruise?
 
Oh crap, you're right. So on my non-cruise, tick-tock-tach car, my tach wire goes where your cruise wire goes....and your tach is through one of my un-used dimples. I wonder why Mopar didn't just use the same hole for all tach wires??? Why didn't they just run your factory cruise wire through what is your tach hole & keep your tach wire in the same place as mine???

Is your car original tach/cruise?
Yes mine is a factory equipped tach/cruise car. I cant tell you for sure if anything changed from 1968 (mine) to 1970 (yours) on the tach/cruise.
 
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fyi- since I'm now running a Dixco hood tach, I'm going to remove my factory tick-tock tach wire & run my cruise wiring through that same hole...no new holes.
 
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