Heater Plenum Advice

[Jeff10]

Hey Everyone,

I know I'm likely to get a few negative comments; but, I would like honest opinions about a current predicament.

One of the shops that worked on the Bronco the last 6 years likely cut the lower heater box to clear the NP435 shifter. I am attaching a pic showing the lower side of the box.

After first discovering it I was a little PO'd; but, as I thought through it I came to the conclusion that it might not be such a big deal. I would have expected them to seal it after cutting the clearance. Maybe the extra opening doesn't really affect things too much. regarding air flow from the box.

This is on the Bronco that is pretty close to being for sale, so I'm looking for opinions to make sure I'm not out in the weeds with my opinion.

I should note that the previous owner of the body removed the plenum on the engine side of the firewall, so technically the truck doesn't have a defroster.

If I choose to repair it, it will still look rough. I have read about the heater boxes being modified for NP435s... I just don't recall this part of the discussions.

Thanks,

Jeff

 

[DirtDonk]

Tough call Jeff. On the one hand, it probably has no negative effect on floor heating. In fact, it might even add more effective blowing around the cabin, even if it does reduce velocity somewhat.
What about sound? They're noisy enough as it is, but does this add any additional noise during use?
And for a literal "hack" type job, they actually did a fairly clean job of it. The whole plenum looks like it could use a good painting though!

Maybe that last is your answer. If you want to seal it, you can do a reasonable job with whatever you have, then paint it up to make it look more legit.
Or perhaps even the sealing job could be accomplished by using a sheet of one of the sticky-backed insulating materials. You know, like DynaMat or Boom Mat or one of the similar products.
Kill four birds with one stone.
1. sealing
2. cleaning
3. noise reduction
4. insulating

You could patch it with fiberglass easily enough, but that seems a bit more work to me.

Paul

 

[Johnnyb]

I have a NP435 and no need to cut heater - just bent the shifter to clear.

 

[DirtDonk]

Yeah, that's the more common mod for sure. But I've heard/seen others that cut the plenum. Been awhile though.

Paul

 

[Jeff10]

Hey Guys,

Thanks.

Yes.... Hindsight is 20-20. lol

@Paul - My plan (maybe the easy way out) is to try to make any necessary repairs with the box installed. I'm not sure how easy that will be with it sitting like it is.

@Johnnyb - If it was the last shop that did it, they may have done it in an attempt to install the Gear Banger shifter. That install was never quite right so we went back to the longer shifter. I wasn't asked about cutting the box. I'm really not sure who to blame.

Thanks,

Jeff

 

[73azbronco]

I think that cut kills' the defrost option flapper?

 

[DirtDonk]

I'm really not sure who to blame.

Oh, I do. The person who cut anything without asking for permission first!

 

[Broncobowsher]

Blown out of proportion. Nothing wrong, ignore it.
Defrost performance? Pull the cable and see where that flap lands. From what I see I am 99% sure that it isn't into the flapper area.

Back when I did the NP435 I found the interference the first time I shifted into granny. It snapped that corner off the heater plenum. Wasn't even a nice notch like you have. Just punched into the plastic and self clearanced. Didn't change anything about the defrost flapper.

Even if it did leak a little air, it is only a little bit of air. It is just the defrost, it will still work. There is probably more of a loss of airflow from the foam seal rotting away and leaves and hairs n front of the heater core, but it still works exactly the same.

 

[Jeff10]

Hey Everyone,

Thank you for your input.

@Broncobowsher - I appreciate the first hand account about your NP435.

Jeff