Electric Choke Power Source?

[ramblinn]

69 440RT, installing Edelbrock 800 CFM Thunder AVS with electric choke.  Researched here and moparts, most suggest IGN1 blue line to ballast R for power.  I'm using a Firecore RTR dizzy which requires ballast bypass so essentially the IGN1 line to ballast is direct to coil+ and the instructions state not to power the choke from the alternator or coil.  Edelbrock says to use the wiper motor. 

Seems like the only true engine run power source would be an oil pressure switch, but that won't work on a rallye dash with the oil gauge setup.  Would using a std bosch spdt 30amp triggered by the coil+ line, with choke powered from the alternator batt lug, be a reasonable approach?  Just have to remember not to keep the ignition switch in run with engine off (same as wiper motor).

[John_Kunkel]

I always use the blue wire on the voltage regulator, it's a parallel circuit to IGN1. Some folks seem to think that the choke heater draws too much current and will rob the ignition but that's never been a problem for me.

[BLK 68 R/T]

If you're bypassing the ballast, you will be tying the IGN 1 and 2 wires from the ballast together, correct? No reason not to tie into it for your choke power.

[ramblinn]

If you're bypassing the ballast, you will be tying the IGN 1 and 2 wires from the ballast together, correct? No reason not to tie into it for your choke power.

Yes, I replaced the resistor with a #6 wire to keep the stock look.  Was thinking some more about this and remembered there is a threaded plug in the rear of the block adjacent to the threaded opening for the stock oil gauge sender.  Assuming that hole is exposed to oil pressure, I could use an idiot light oil sender to control power to the choke.

[Nacho-RT74]

idiot light sender and gauge senders sends ground/negative

Since you kept the ceramic, I'd still hook up the choke to the blue wire on reg or ballast plug ( the one coming from bulkhead, not the one to coil ), just for "correctness"

you can either use an idiot light sender and a relay to power on the choke power just whe engine running, OR use a later oils sender with this function built in, which in fact was used on laters Mopars. They are 3 prongs units.

it is just like this, BUT the middle prong feeds the oil indicator on cluster, not any Starter relay. Pic is just referential to show how they look, not saying the on you need it works exactly like the diagram shows ( althought it could work ).



it will be used of course to the choke and not to any gas pump.

NOTE, I'M PRETTY SURE THE S STANDS FOR SENDER AND NOT STARTER

[Nacho-RT74]

Maybe those with 2 prongs works like an in and out and will work to you since you actually won't need the light sender prong feature...



just need to be sure about what kind of signal drives and they are isolated from chassis, being activated or not.

something like this:



I can't tell which one will work like I'm telling but giving ideas.

and of course you can use the extra block provision for it.

presostatic switch used on A/C dryers works just like that, but I guess on diff pressure rates.

I think you got the idea!!!!

[ramblinn]

Good stuff, thx!  

I think this should be the ticket.  Really want to stay away from ignition circuit, though I think that would work especially with power relay.  Only risk is someone (daughters car) leaving ign in run.  

Found a Wells oil pressure switch spec, looking for normally open, close at low oil pressure (like your diagram).  Assuming thread (I'll verify) is same (1/8-27npt), came up with a couple candidates. One of them, PS114, in stock at local Autozone.  Only question is physical size fit...the existing oil pressure gauge sender fit is tight.

 

Would still use the bosch to switch power.  PS114 would trigger the bosch.  Circuit diagram is forming in my brain  

[Nacho-RT74]

You don't need to worry really about the load on ign circuit. Stock systems are like that! Really. Don't overthink the deal . My 74 in fact gets the choke source spliced from same alt positive coming from ign switch ( since 70 the positive field is feeded straight from ign switch run circuit), and is factory setup


Aaaand will fit. They are waaaaaay smaller than the gauge kind senders. About same size of the idiot light sender.

[John_Kunkel]

I don't see the need to run the choke heater feed through a pressure switch; sure, if you leave the key on without the engine running, the heater will be drawing current but isn't that what ACC is for? No need to have the key in RUN with the engine off.

[Nacho-RT74]

But just accidentally letf in RUN

[A383Wing]

Stock choke connection on many of the Mopar cars from the 70's to the 90's is taken straight off the "RUN" circuit at the ballast resistor or the voltage regulator...I think it's the blue wire..., no switch or relays were installed back then

And those little electric choke coils do not draw that much power

[ramblinn]

Copy all, but hey I'm committed   

Discovered the hole opposite the stock sender is 1/4NPT vs 1/8NPT for the stock hole.  So since I bought a 1/8NPT light switch, gotta pick up a 1/4-1/8 bushing.  The light switch is much smaller than the gauge sender, fortunately since there is less clearance as the valley pan rear rail slants to the rear on right side. 

Thought about pulling power for the switch from the horn relay, but since it is always hot a switch failure in closed position could zap the battery.  Maybe I can't read a schematic but doesn't look like the wiper motor (3 speed) has power until the wiper switch is used.?.  So will run a trigger line for power relay from acc in fuse box.  Then power the choke from the batt terminal on alternator with a fuse.  Relay location just below horns.   

[Nacho-RT74]

ballast or regulator blue wire ( not the one with brown wire spliced into, just for correctness )... stop overthink it LOL

and no need for relay . The relay idea was just IF the turn on trigger was to be a negative signal, not due load added by the choke thermal coil

attached diagram is how it was the ign1 circuit traced from factory since 72/73. It included the choke signal splice on it, on the run to alt field ( elect reg with daul field alts ) . no need to worry about

The oil pressure switch is a nice add thought