Weird Device On Firewall.


Dec 5, 2009
Hey guys!

I saw this while looking under the hood and cant figure out what it is and what it does.


I plugged it in but nothing changed.

Anyone have any idea what it is?


I found this wire underneath the distributor. Wondering what it's supposed to connect to. It looks like he may have rewired it as there is a wire near it the same color. I tried tugging on the disconnected one, but it was still ran so I didn't mess with it:


Any idea what it goes to?


- Brandon
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Anything? The first picture is talking about the part on the left of the picture, that wire in my hand is supposed to be plugged into it I believe.

- Brandon
Ballast resister on FW?

What year? Did this car have points style ignition at one time? Could the part on the firewall be the ignition ballast resister?

If the car has been converted to HEI (or other system that does not use points), then the ballast resister would not be needed.
On the device...I'm going to have to find my Chilton's to look that up. Does it have vacuum lines attached to it? What is the yellow thing...a dial or a cap? That red wire does not have a factory connector on the end. That's a pretty heavy wire too. You may have to trace the wires to see what they connect to. I don't recall anything like this in either my '76 or '78 2.3L engine compartment.

The wire by the distributor is unfamiliar also. Where does it route to? I would wrap the connector up in electrical tape until I knew what it did. Are there wires on both your oil pressure and water temp senders?
Thanks for the detailed answers! Even though they really didnt answer anything haha. Its giving me a good place to start. And yes it's a 4 banger haha. It gets incredible gas mileage =)

Oh he's a 78 by the way.

I didn't try turning it but I do remember it doesn't push in. And I noticed the cheap auto zone connector on it so I knew something had been tweaked. I'll try to get out there tomorrow and see if it turns or if it has a vacuum line on it. I don't believe it did. But I could be wrong.

As far as points go, I bought this car already tuned up. But from the looks of it he went to HEI or nonpoint, but didn't replace the blaster for some reason. The cap and rotor were changed to my knowledge.

Come to think of it, I have nothing to do right now, so I'll go check real quick. BRB with the answers haha.


- Brandon
Ok so I was wrong

The module on the firewall has 2 vacuum lines running to it, and the yellow thing does turn (not sure if it actually does anything though haha). I couldn't chase the lines as its pouring rain outside.

And the yellow wire near the distributor chases back to the harness connected to the back of the alternator. Can't see where it should connect though.

Making progress!

Thanks again!

- Brandon
The cap on the thing on the firewall is probably a vent for the solenoid and whatever vac circuit it operates.

If the wire by the distributor traces to the STA terminal on the alternator more than likely it's for the electric choke.

Ok guys I checked it again today.

The module's vacuum lines run to the vacuum tree, and the other runs into the left fender and I can't see where it runs from there.

About the electric choke (possibly) option. I've been wanting to do this because I HATE manual chokes. I can never remember to turn them off, and I end up wasting gas all the time. How can I convert?

Thanks guys!

- Brandon
Brandon, if you have the factory carb, it has an thermostatically controlled automatic choke. The electric wire is for a heater that brings the choke off earlier. The automatic choke should work fine without the heater, but will take longer to come off.
Well it was a brand new carb that was put on, and looks like a factory rebuild. Its ran on a mechanical choke, so how would I connect the electric choke?


- Brandon
The easiest way to add the electric choke heater would be to find one on a donor car, although it may be that Holley or another manufacturer has a generic kit for sale.

Your automatic mechanical choke should work just fine if adjusted properly, the electric heater is just to get it to open sooner for improved emissions.

Of course a choke system on a carb will never start as well as an electronic fuel injection system. I'm sure that my kids are just not going to understand why my old car doesn't start as well as their newer EFI car does...
The module's vacuum lines run to the vacuum tree, and the other runs into the left fender and I can't see where it runs from there.

I think you mean the other left? L-R is as inside the vehicle.

Purge or control for the carbon canister?

About the electric choke (possibly) option. I've been wanting to do this because I HATE manual chokes. I can never remember to turn them off, and I end up wasting gas all the time. How can I convert?

First the choke needs a heater tube from the exhaust manifold. Usually from the choke housing to the manifold.

Electric heater in the choke would require a compatible donor, maybe just the cap and spring, maybe also the housing.

I've also seen brackets on the choke housing for holding a bypass/ heater hose against the choke cap.

Mostly you need to make sure the high idle cam is engaging the bracket on the throttle shaft and the choke is properly adjusted.
Yes I meant the other left haha. The passenger side fender is where it's ran, and I have no idea where it goes from there.

As for the choke, yes. A braided cable from under the dash.

- Brandon
I guess we need to figure out which carb you have then. I've never seen a factory 2.3L with anything but the Holley/Weber 2bbl (Motorcraft 5200) and its automatic choke.

I've attached a pic of an aftermarket Holley-Weber carb with the automatic choke and water heating fitting on the side. This one is similar to what came on the MII 2.3L for all years. The electric heater is a disc that fits inside the choke housing and is sealed from the water flow.

If yours looks different from this we need to check for serial numbers, etc.

If your carb does look like this but is missing the automatic choke housing, then a trip to the junkyard or some eBay shopping could supply what you need.


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Ok I took a look outside and found what I believe is the part number.


I checked the spare one in the trunk, and the whole choke assembly was pulled off, showing the spring and lever inside the black plastic piece. So I had nothing to reference it to at the time haha.

Does that help any?


- Brandon
I couldn't find a tag. But I checked my spare one in the trunk, and it was a reman with the same stamping, but on the base one the passenger side it's stamped r8705

Now....on the one I'm running, it's stamped R7909. As far as I can see without pulling anything else off.

Help any?

Also...I found this doing a search for the original stamping i posted (12R7431B):

I found two '74 Pintos with carbs. I went and got both of them
for $20 each. I brought them home and cleaned them up. They are
in really good shape. They both fit on my manifold, but I cannot
find any markings to tell me if they are Weber or Holly. Both
have removable jets. One is a hot water choke and one is the
electric choke (which one is better)? both have a 27 stamped on
the side of one of the barrells. Both carbs have Motorcraft
stamped on them. Th electric has a stamp on the base R8713 and a
stamp on the float bowl 12R7431B. The Water choke carb has
stamped on the base R6995 and on float bowl 12R6070 B. The one
with water choke also has a metal tag on the top bolt that is
stamped Motorcraft D52EDB . I understand Weber licensed both
Holly and Motorcraft to sell these carbs, but I need to figure
out exactly what I have in order to get rebuild kits and parts.
BTW I am putting it on an 1800 (still in rebuild).

I searched that link you posted as well. I founf that R7909 under the 5200C (like you stated), from a 77-81.


- Brandon