12v dc 30 amp variable blower speed control

[HVAC Tech]

I'm having issues with my trucks air conditioning because of the blower resistor failing frequently. There was a problem with the grounding to and I want to know if it is possible up install a variable speed control to run the blower in my truck. I know the ac won't come on when I turn the blower on but that isn't a problem. Just want the fan to run when I turn the switch on. A simple 30amp toggle would work but I think a variable speed blower would be nice top have. Amy help would be appreciated. Thanks

 

[KeepItSimpleStupid]

This product isn;t suitable, but it does give ou an idea of what you need. A PWM speed control, 30 A, 12 V. Take a look at the instruction manual.

I did briefly have one of these connected to a 1982 vehicle blower, but not permanently. It did "sing". e.g. made audible noise. The frequency of the PWM has to be played with.
This particular unit does have a slow-start feature.

GM desiged a $5.00 part for some vehicles to prevent water from entering the blower housing through the cabin air filter. Some blower resitor models apparently have issues. Yoic an check out Rockauto for parts. They have a good choice of brands and price points usually.

ebay and Nuts and Volts Magezine typically has advertisements.

Usually the blower switch works on high when the resistor breaks. Check the brushes. I've made brushed from stock from a vacuum cleaner store. They had the best selection of brushes. The stupid GM resistor needed a swivel socket to do the job the fastest. Just remember, like I didn't 4 mm and 5/32 are nearly the same.

One search came up with: https://www.canakit.com/30a-motor-speed-controller-pwm.html

 

[HVAC Tech]

Thanks for the info. Just as a side note, I had an electrician friend of mine look at the truck and he turned me on to a web site that I hadn't seen before. This site will search wrecking yards in the U.S. and Canada. Maybe even other countries, not sure. All you do is put your VIN number in and tell it what your looking for and it will list the part according to condition, price, and distance from your location to help calculate the shipping. I think that the wrecking yards have to be a member of the site so all the wrecking yards are not searched but you will be surprised by the results.. It's car-parts.com enjoy

 

[HVAC Tech]

The VIN search didn't come up on my mobile but did on my desktop.

 

[KeepItSimpleStupid]

I used one too, recently and it could have been that one, In both cases I had issues with electrical parts. 1) The car amp I go was supposedly good, but the two front channels were out. No offer to replace. That $30 was better than $300 and a radio that doesn't work depending on ambient temperature.

2) The other one for for a $10 (with shipping) dichroic mirror. The first was the wrong one, period. They did replace with a defective mirror (Dome light circuit), but the best option is to have the mirror rebuilt for $100+shipping which I did.

In general, electrical parts are non-returnable.

 

[KeepItSimpleStupid]

I found this site https://www.4qd.co.uk/faq/index.html These guys look at the complications when applied to propelling a vehicle, not necessarily a simple fan controller.

 

[Mosaic]

I have Japanese vehicles and recently i had to replace an AC blower squirrel cage affair (Nissan) cuz the bearing failed. The unit had a built in PWM controller with 6, K305, MOSFETS on a small low profile finned heat sink (1" x 3" with 8, 0.25" tall , 0.125" spaced fins) cooled by the same blower outlet. I salvaged the PWM unit as I got a complete blower and PWM as a single scrapyard item for $40. The circuit used two 15A fuses, seems the motor had 2 coils, 3 connections, when the motor jammed it took out both 15A mini spades.
If your motor has multiple coils u can use switches to activate them and obtain different speeds.

PWM for fan motor automotive use is fairly efficient and reliable:
**broken link removed**

I don't see a link to a DIY circuit though. Once u can cool the circuit with the A/C blower it's more than doable with a TL494 PWM controller and a couple beefy mosfets like IRF3206 units.

It is probably also possible to locate the stock resistor in the A/C blower path to prevent it failing, or if you can get scrap resistors, gang two parallel pairs of stock units in series to get 4x power handling and you're done.

 

[kinarfi]

I recently noticed that my class A motor home had only one speed, HIGH, so I built this PWM and installed it, It ran very well, It goes between the motor and the switch on my rig, or it could go between the battery and motor.
1st resistor is not bypassed

 

[Mosaic]

Kinarfi, what's the current drain and heat sinking (You're switching the high side so....Rds not so good) arrangement? I presume L1 is a ferrite bead?
So you're running a kind of open loop, selectable DC, PWM based on the 555 timing?
You don't have any local fusing or PTC so I suppose the MOSFET can pop the auto fuses without dying?


Can u share the MOSFET and multiposition switch model for spice?

 

[kinarfi]

You should already have the switch, I had to dig and search for the Fet. Yes, that just a ferrite bead.
The fan is chassis grounded requiring high side control, the 555 seems to be a good FET driver and Irf4905 has an rdon of 20mohm. I'll take a photo of the assembly in about an hour or so and add it to the thread.
I later found the resistor bank had lost connection and I corrected that and removed the FET, I still have it and I can hook it up to another motor and see what heat is generated.

 

[HVAC Tech]

I'm sorry, I can not open the .asy file. Any help would be great.

 

[KeepItSimpleStupid]

It appears to be a typo. When I looked inside, it appears to be an .asc file which should open in LTSPICE (free) from www.linear.com

 

[kinarfi]

sw_5_to_1.asy
it's an assembly file