3B intake manifold heater (1 Viewer)

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image.jpg
So this is the manifold intake heater ( the upper wire if the two glow plug wires) which is attached, as far as I can tell, to a sort of glow element in the manifold. The PO installed a Wilson switch for the glow plugs and a toggle for the intake heater. I didn't take it out so other than voltage drop I'm not certain it works. The 3b manual is very vague.
1. When does one use it and for how long?
2. Does it heat only the one intake runner?
3. Is this associated with a certain era or vintage of 3B? I think is from a BJ 70 but I'm not certain. thanks!
 
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That should be just an insulating terminal for the glow plug buss bar. Thats about how my 3B's have looked. And as far as I know the 3B didn't have an intake heater....just he 13B-T's
 
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It's a resistor for the superglow system, used in the delivery of 12V and 6V to the glow plugs. Does not heat anything.
The 3B didn't have anything in the intake to heat the air, so unless there is some kind of aftermarket heater installed? there shouldn't be anything in there between the venture (butterfly) and intake.

diag_ARjK0P.JPG
 
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I thought a glow plug WAS a resistor. Here's a photo of it out of the manifold.
image.jpg


And for scale :
image.jpg


It's hard to see, but the top threaded section is insulated from the rest of it, and serves as a place to connect the glow plug bus bar. The wire attached to the lower part is insulated from the threaded portion and appears to ground out through the resistor just like a big glow plug. The glow plugs and this thing each have their own power supply from a relay. As I see it I could either replace this resistor/heater, abandon it, or attach both wires from the relays to the glow plugs so I have a momentary or toggle Wilson switch. As I doubt I'll be able to find a replacement part and no one seems to think its very necessary I may do the latter. Will I hurt the unpowered relay if it is backfed power while it is not activated?
 
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As Fantom says, it's there to be used as a "dropping resistor" to drop the voltage to your glow plugs.

Sure it does indeed get hot when doing this job, but providing heat to the intake manifold is not it's real purpose.

It is needed if you a running "superglow preheat" (which that engine was obviously manufactured with).

But with different plugs fitted (from original spec) you can run a simpler form of preheat, discard this dropping resistor and plug the hole. (Or just leave it in place unconnected to plug the hole)

:beer:
 
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Thank you both. Thank you especially Tom for your frequent and learned postings here, I almost always come across your name when searching almost anything.
So did they put the resistor in the manifold just as a convenient place to dissipate heat? As I understand it, when the truck had a glow timer it sent 12v through the ifs for a time then switched to 6 volt running it through this resistor. That's why there are two relays and two power sources to the glow plugs. Cool, thank you
 
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.... So did they put the resistor in the manifold just as a convenient place to dissipate heat? ....

Yep.. And of course what little heat it does impart to the manifold and intake air is of mild benefit for starting under cold conditions as a bonus.

:beer:
 

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