Replaced almost every heater component. Cab is blistering hot now

[special-K]

Originally Posted by Mister-B

Unless the aftermarket blower draws more power, because it is bigger (which it is), or is more powerful (which it very well may be, where it blows harder).
Posted via Mobile Device

You never mentioned the motor you put in was anything different. The point is really quite simple. Put the fuse of proper amperage for whatever blower you are using. My explanation was based on OEM. If you checked and know your replacement requires a 25a fuse you are fine.

If you do have a 10a fuse in the next one down (radio),you better change that back to a 3a,as required.

[Mister-B]

Originally Posted by special-K

You never mentioned the motor you put in was anything different. The point is really quite simple. Put the fuse of proper amperage for whatever blower you are using. My explanation was based on OEM. If you checked and know your replacement requires a 25a fuse you are fine.

If you do have a 10a fuse in the next one down (radio),you better change that back to a 3a,as required.

Actually, yes I did. Go back and read post #15. I said the new motor is longer, and I couldn't get the hood hinge back on with the same tools because there wasn't as much room as when I removed the old motor.

I also said later on that I was guessing what type fuse the radio had, but had never touched it, so I wasn't worried
Posted via Mobile Device

[special-K]

Just trying to help,not pick this thread apart. If you know your new longer motor requires 25a you are fine. If you are assuming based on the larger size,you could be asking for trouble. I'm pretty sure (disclaimer) you never stated you know in fact that the replacement motor is 25a. The OEM system for A/C is 25a (2.5x larger than non-A/C) because you are running more components on that circuit,like a compressor,when the A/C is running. I'm doubtful any blower motor in this realm would draw that much alone. I could be wrong. Just hoping we don't see an electrical meltdown thread in the future

[Mister-B]

Originally Posted by special-K

Just trying to help,not pick this thread apart. If you know your new longer motor requires 25a you are fine. If you are assuming based on the larger size,you could be asking for trouble. I'm pretty sure (disclaimer) you never stated you know in fact that the replacement motor is 25a. The OEM system for A/C is 25a (2.5x larger than non-A/C) because you are running more components on that circuit,like a compressor,when the A/C is running. I'm doubtful any blower motor in this realm would draw that much alone. I could be wrong. Just hoping we don't see an electrical meltdown thread in the future

Thanks. I appreciate that. No, I don't know for sure that the new motor specifically asks for a 25 amp fuse. What I do know, is that it is a bigger motor, and that it blows quite a bit harder than the old one. I know that it had a 10 amp fuse in the heater/AC slot, and that it blew a couple minutes after I installed the new motor. When I switched it to a 25 amp fuse, everything has worked fine.

So, that being said, how would I go about verifying that there isn't some other type of issue? I don't want a meltdown, and would like to avoid it, but at the same time, this fuse box does allow for both 10 and 25 amp... The difference being whether the truck has AC or not, so maybe this is within an acceptable range still. Also, I checked Brothers just now, and they show the blower motor is the same, whether the truck has AC or not. http://www.brotherstrucks.com/prodin...number=HTRM072 it seems like if the blower motor is the same, regardless, that using a 25 amp fuse (which that spot is rated for) would be fine, but I'm open to opinion here, and would appreciate any direction
Posted via Mobile Device

[camrycurt]

It's hard to find a true heater-only blower motor. I looked and couldn't find one; everywhere I looked only sold one version for our trucks, the 25 amp A/C motor.

Running the A/C blower with a 25 amp fuse won't damage the blower motor, the problem may be that it will eventually burn up your fan speed switch. That switch is meant to run in the 10 amp heater system so may not like the higher amperage. I've read where some guys never have a problem but others do, so it's just something to keep an eye on.

I think those of us running heater-only trucks are simply out of luck in finding an aftermarket blower motor. If someone finds one I'd love to know, because mine is weak and squealing and I'd love to replace it.

I guess one solution would be to bypass the stock fan switch with a new one that could take the higher current. It may be worth seeing if a new switch could be wired into the system and made to work.

[Mister-B]

Originally Posted by camrycurt

It's hard to find a true heater-only blower motor. I looked and couldn't find one; everywhere I looked only sold one version for our trucks, the 25 amp A/C motor.

Running the A/C blower with a 25 amp fuse won't damage the blower motor, the problem may be that it will eventually burn up your fan speed switch. That switch is meant to run in the 10 amp heater system so may not like the higher amperage. I've read where some guys never have a problem but others do, so it's just something to keep an eye on.

I think those of us running heater-only trucks are simply out of luck in finding an aftermarket blower motor. If someone finds one I'd love to know, because mine is weak and squealing and I'd love to replace it.

I guess one solution would be to bypass the stock fan switch with a new one that could take the higher current. It may be worth seeing if a new switch could be wired into the system and made to work.

That makes sense that they would just sell one blower now for both AC and heater only trucks. Less manufacturing costs.

I called Autozone just now, where I bought the blower motor. The guy that I talked to has owned 3 67-72 Chevy trucks, so he was helpful and knew his stuff. He looked up the blower part number, and said it is the same part number for AC and heater only trucks. He said running the 25 amp fuse sounds right, and if there were a problem, something would have happened fast. I ran the truck for about 20-30 minutes at full heat, full blower speed, and full defroster speed, and didn't have any problems.

They really should sell these blower motors with a 25 amp fuse, and some sort of explanation IMHO.

I'll keep an eye on it though
Posted via Mobile Device

[Stocker]

Originally Posted by camrycurt

Running the A/C blower with a 25 amp fuse won't damage the blower motor, the problem may be that it will eventually burn up your fan speed switch. That switch is meant to run in the 10 amp heater system so may not like the higher amperage.

This isn't quite correct -- using a 25A fuse (instead of a 10A fuse) won't cause the motor to pull more amperage. The motor will use the amps it was designed to use. If the motor was designed to operate in excess of 10 amps, a 10A fuse will blow. If the motor is designed to operate at less than 10 amps, using a 25 amp fuse will not make it pull any more amperage.

The current through the switch will be the same, regardless of which fuse you use.

Of course, if you use a motor that requires more amperage than the switch was designed to handle, that could damage the switch.

[camrycurt]

Cool, Stocker, thanks for the clarification. I think the two motors are actually different, which is what makes it difficult because no one sells a replacement heater-only motor.

From another thread I remember member 48richard quoting the 71 service manual which says that the heater-only blower draws 6.25 amps and the A/C blower draws 16.5 amps. I guess that's why the new motors blow the 10 amp fuses so quickly. The question is whether that extra 10 amps is enough to cause problems.

Anyway, I think Mister-B is right to keep an eye on it and the search continues for a true 6.25 blower motor!

[Mister-B]

Originally Posted by camrycurt

Cool, Stocker, thanks for the clarification. I think the two motors are actually different, which is what makes it difficult because no one sells a replacement heater-only motor.

From another thread I remember member 48richard quoting the 71 service manual which says that the heater-only blower draws 6.25 amps and the A/C blower draws 16.5 amps. I guess that's why the new motors blow the 10 amp fuses so quickly. The question is whether that extra 10 amps is enough to cause problems.

Anyway, I think Mister-B is right to keep an eye on it and the search continues for a true 6.25 blower motor!

If you're that concerned about the switch, why not split the difference by using a 20 amp fuse, and get the readily available heater motor?
Posted via Mobile Device

[Stocker]

Originally Posted by Mister-B

If you're that concerned about the switch, why not split the difference by using a 20 amp fuse, and get the readily available heater motor?

If you can find a motor that uses just 6.25 amps (using camrycurt's info), then it can be protected by a 10A fuse. It will pull a maximum of 6.25 amps, whether you use a 10A fuse, a 20A fuse, or a 25A fuse. Nothing will be gained by using a 20A fuse, and a margin of protection will be lost.

[Mister-B]

Originally Posted by Stocker

If you can find a motor that uses just 6.25 amps (using camrycurt's info), then it can be protected by a 10A fuse. It will pull a maximum of 6.25 amps, whether you use a 10A fuse, a 20A fuse, or a 25A fuse. Nothing will be gained by using a 20A fuse, and a margin of protection will be lost.

No, I'm saying he could get the AC/heater blower that is readily available, and use a 20 amp fuse instead of a 25, since he says he's worried about the control switch, which would lower the likelihood of something happening.
Posted via Mobile Device

[Stocker]

Originally Posted by Mister-B

No, I'm saying he could get the AC/heater blower that is readily available, and use a 20 amp fuse instead of a 25, since he says he's worried about the control switch, which would lower the likelihood of something happening.

That is exactly what you said, and I misread it, sorry.

Back on topic, however, and using the info supplied by camrycurt --If your new motor pulls 16.5 amps, it will pull 16.5 amps whether you use a 20A fuse or a 25A fuse. There will be no difference in current draw if you use a higher capacity fuse.

That 16.5 amp current is more than 2 1/2 times the current that the switch was designed for, assuming that your OEM motor pulled 6.25 amps, and that the switch was designed to control that 6.25 amp motor. This explains camrycurt's concern for the switch when using a motor that requires more current than the original motor.