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Heater Motor Upgrade

904Bronco

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Sep 28, 2004
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San Martin, CA
So the heater box is like the volute in a centrifugal pump... The impeller/blower cage has to be placed appropriately in the housing to work correctly. If it is not then you get reduced flow and noise. The best way to do this is to remove the heater box and do a tear down rehab and relocate the fan in the housing.
I looked though my pictures but did not find the definitive one, sorry.
 

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DirtDonk

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My guess is a little more than stock. And some users have had to up-size their fuse to 25a just to keep it from blowing when they use other accessories. This could easily be explained away by variations in the condition of the wiring overall though.
A Bronco with corroded fuse contacts and wire connections and questionable splices could easily use more amperage than a perfectly good harness would need.

And whatever other circuits are sharing that fuse could be putting more on as well. It's good to know that mpboxer did not have to put in a larger fuse. That lets us know that if there is a difference, it's minimal.

Paul
 

sprdv1

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I'd think it was minimal as well

Probably could google the differences
 

70 sport WA

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Nov 1, 2003
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768
Wow, blast from the past. Did it maybe 16 years ago and great upgrade. Parts option on page 17 (with parts numbers) and highly recommended. Take a little off the box at a time (enlarging the circle hole for the squirrel cage) and leave enough room for the new screws.
 
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CincoBravo

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Oct 14, 2018
Messages
133
Loc.
Oxford, MS
Alternator Question

My heater core was leaking so I took out the whole box and then went down the rabbit hole of this thread. So, I don't know jack about electrical, but I read somewhere in this novel that the upgraded motor (p/n 35587 from multiple parts stores) might overpower an alternator if that part hasn't also been upgraded. I'm posting some pics of my alternator. Can someone tell me the output of my current alternator (it's a Motorcraft) based on the stampings in the casting? It looks like it says 15V 40A, but that doesn't seem to jive with other searches I've done saying the Broncos came with a 60A. Can anyone tell me if my current alternator will play nice with the upgraded heater motor?
 

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DirtDonk

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I didn't know any Early Bronco came with a 60a alternator, but perhaps that's what they meant when the sticker said "heavy duty alternator" maybe.
What year is your Bronco? It's entirely possible that it came with a 40a model when new, and certainly possible that when someone changed out a bad old alternator they put in a low output model to save money.
There were 40, 45, 50 and 55 amp models back then, and maybe even 60 but I always thought the 60's were aftermarket upgrades as the manufacturers and rebuilders started putting more and more high-output parts in their units.

Either way, there's no way to know about yours anymore, without testing it.
It could have been an up-rated rebuild where the rebuilder did not re-stamp the housing. It could also be very tired and not quite capable of putting out it's original 40a output.
While you're this far in, you might as well take it in to your favorite local parts store that has someone that knows how to use the test equipment. Or if you don't have one of those, perhaps an auto-electric shop nearby?

Even though the heater blower motor itself is not too much for the alternator, when you start adding things like headlights, engine running, hazard flashers and radio working, a 40 is definitely working at a deficit.
If yours tests out weak, it's time for at least a 60 or 65 amp model as a direct replacement without changing any wires.

As I'm sure you've seen here, you can also up-size to the original large-case 1G for 70a or 105a outputs, or just jump right to a 3G model with internal regulator and go with a 95 or 130 amp model.
Or look for a stock replacement that's been uprated to 100a or so that will bolt right on.
Lots of choices, but any one of those with more than 70 or 80 amps output, or with a different case design, is going to require some additional wiring on your part.

Paul
 

mpboxer

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Can anyone tell me if my current alternator will play nice with the upgraded heater motor?

I can’t tell you if your 40amp will play nice, but if you wanted a stock 65amp replacement I can tell you mine has had no issues. I had to verify but I have a remanufactured Duralast 7078 with no issues. I only have H4 headlights, a single head unit and retro sound speaker on my system though. Stock wiring and fuses.

Mike
 

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CincoBravo

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Messages
133
Loc.
Oxford, MS
I didn't know any Early Bronco came with a 60a alternator, but perhaps that's what they meant when the sticker said "heavy duty alternator" maybe.
What year is your Bronco? It's entirely possible that it came with a 40a model when new, and certainly possible that when someone changed out a bad old alternator they put in a low output model to save money.
There were 40, 45, 50 and 55 amp models back then, and maybe even 60 but I always thought the 60's were aftermarket upgrades as the manufacturers and rebuilders started putting more and more high-output parts in their units.

Either way, there's no way to know about yours anymore, without testing it.
It could have been an up-rated rebuild where the rebuilder did not re-stamp the housing. It could also be very tired and not quite capable of putting out it's original 40a output.
While you're this far in, you might as well take it in to your favorite local parts store that has someone that knows how to use the test equipment. Or if you don't have one of those, perhaps an auto-electric shop nearby?

Even though the heater blower motor itself is not too much for the alternator, when you start adding things like headlights, engine running, hazard flashers and radio working, a 40 is definitely working at a deficit.
If yours tests out weak, it's time for at least a 60 or 65 amp model as a direct replacement without changing any wires.

As I'm sure you've seen here, you can also up-size to the original large-case 1G for 70a or 105a outputs, or just jump right to a 3G model with internal regulator and go with a 95 or 130 amp model.
Or look for a stock replacement that's been uprated to 100a or so that will bolt right on.
Lots of choices, but any one of those with more than 70 or 80 amps output, or with a different case design, is going to require some additional wiring on your part.

Paul

Thank you Paul. My truck is a ‘77, but chances of that alternator being original are likely slim. Thank you very much for the detailed answer. I'll be taking your advice and have it tested. I appreciate the help.
 

CincoBravo

Jr. Member
Joined
Oct 14, 2018
Messages
133
Loc.
Oxford, MS
I can’t tell you if your 40amp will play nice, but if you wanted a stock 65amp replacement I can tell you mine has had no issues. I had to verify but I have a remanufactured Duralast 7078 with no issues. I only have H4 headlights, a single head unit and retro sound speaker on my system though. Stock wiring and fuses.

Mike

I appreciate the response Mike. It's good to know I don't have to go so far as the 100A units others in this thread have mentioned having.
 

sprdv1

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I appreciate the response Mike. It's good to know I don't have to go so far as the 100A units others in this thread have mentioned having.

for sure...

noticed your oxford, ms...

i have relatives in water valley, and family resides in canton
 

broncobuddha

Jr. Member
Joined
Apr 9, 2007
Messages
198
I mean isn't it that time of year again? Lol.

Found this thread when doing research as I'm going through my heating setup.

This thread makes me want to put a stock box back in haha.

I ripped the stock box out YEARS (over 10 easy) ago and put in an Accu-Heater. Defrost ducting never really worked so I never plumbed it and just dumped one vent out on the passenger feet and ran a hose over the tunnel to dump out on the driver's feet.

The way my buddy and I had mounted the accu-heat was sort of behind where the glove box was but it hung down and was angled out a bit to make room for the hoses coming through where the old core pipes used to stick out through the firewall.

I yanked everything out today and am modifying it to sit higher since I don't have a glove box anyways. So it will sit more flush with the floorboard/firewall I'm going to use some 90s to run the heater hoses out some sort of grommetted panel I'm going to make to cover where the fresh air vent used to come in (since I've never had a passenger side one anyways) and then go up where the fresh air vent was then over and down to the water pump and engine.

Then I'm ordering a new defrost duct from Toms and am going to run at least one vent to a Y then dual hoses up to that new defrost duct. The other for now I'll probably just vent down onto the passenger floor.

The Accu heat has been nice but it only takes the edge off. So I'm also getting new seals for the top and doors as my bronco is quite drafty which doesn't help. I'll probably do the 195 tstat as I'm not sure what's in there now.

(I do still have my original 73' box in the garage somewhere but I also got rid of all of the knobs and cables back when I was younger and dumber.
 
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