Operating blower motors without keys/ignition on (1 Viewer)

[dan1554]

I'm planning on automating the operation of the cabin blowers. I installed a coolant heater that should trigger the blowers once coolant reaches a certain temperature. The heater is remotely operated, so the fans need to run without keys in the ignition.

My best bet right now is that I can simply bypass the original switched relays with power from my own unswitched relay.

In an ideal world, the original relay signal would be switched by the ignition but the fan power would be direct to the battery. This way I could run a low amp line to trigger the existing relay and be done with it. Again, I'm just assuming that isn't the case and I'll have to run my own power.

Also, does anyone know how the resistor pack will affect operation?

I'm planning on getting under there with my multimeter this weekend but thought I'd see if anyone else has experience in this area.

 

[goranvolvo]

you can build ignition override and use signal from the heater to trigger the ignition override i m going to look for wiring diagram how to build the ignition override it is easy to do you need some wire and 5 relay

 

[dan1554]

But that wouldn't activate all the switched components? I'd like to keep powered devices to a minimum, since the fans could be running off and on for hours on end.

 

[goranvolvo]

yes if you wire it that way you can wire only the blower

 

[superjuice]

I'm interested in this as well. I would like a thermostat to automatically turn the blowers on and pull in fresh/cooler air without opening the windows. So if the cars baking in the sun it could cool itself off

 

[dan1554]

Found the AC wiring diagram (1hdt but I imagine similar to early 80s). It looks like the circuit to operate the heater relay is switched, but the fan circuit is not. So according to this I might be able to activate the heater relay with a low amp signal from the coolant heater, bypassing the ignition, and get the fan to blow at full speed. I am no expert at reading wiring diagrams however. I think it might be trial and error from here.

**Edit**
Now that I look at it, seems more complicated than that. The resistor circuits are selected by the system amplifier. Maybe just hijacking a blower with my own relay is the best option after all.

 

[dan1554]

So I applied power through a relay directly to the fan's positive connection, assuming that the negative would be handled through the resistor pack and amplifier. I'm not sure what is happening though. It pops my 30 amp fuse almost immediately, and the fan moves but just barely. This is strange because I believe the whole AC system runs on a 30A fuse (drivers side fuse compartment).

 

[dan1554]

Bump in case the right person sees this.

Fan works perfectly when I wire it directly to the battery, but if I leave it plugged in to the factory harness and splice battery power to the fan positive connection the draw is crazy.

Maybe I could use two relays to COMPLETELY isolate it from the A/C system? The fan could work as if it was connected directly to the battery. I just hate the idea of using multiple relays on a circuit. Would look something like this (Both relays should match direction, wasn't sure how to do this in the software):

BIG question - this feels hacky, is there a better way to power the fan with my own switch??

 

[superjuice]

That looks reasonable but you could also isolate the Toyota wiring by installing large diodes instead of the relays/switches. Then it won't backfeed the existing wiring when powering the motor directly. I think it's the resistor that's eating all the juice when you power the motor directly.

Edit: after a better look with the resistor on the ground the diodes alone won't work. You could do one double pole double throw (dpdt) switch or relay to break both connections at once. Motor off the center pins and choice of feed from either of the other two pins.

Toggle Switch Wiring

 

[dan1554]

Great idea! My knowledge of electronics and components is limited. I definitely like having one relay instead of two... My fear was that if there is much of a delay between the relays it could pop a fuse. I will try this as soon as I get some free time.

 

[Tools R Us]

Sounds like a damn good way to kill batteries?

Not sure what you are attempting to accomplish? But, most block heaters don't have a pump, how is the heated coolant going to be circulated through the heaters? Heaters are great radiators, block heaters are good at warming the motor and not much else, most don't have excess capacity.

If the goal is to preheat the cabin, it would be much more efficient to put a small electric heater and plug it in with the block heater? I did this in my unheated/poorly heated VW days, worked well. If it's that frigid, just leave the motor running?

 

[inkpot]

How are you going to pump fluid from the coolant heater into the dash heater?

 

[tweeek]

He's diesel. Look up webasto. They heat the coolant by firing diesel from your tank, and have a built in pump. Think warm truck without running engine, little battery consumption.

 

[dan1554]

I am also looking to reduce the voltage to the fan to reduce speed, noise (for when I'm sleeping in the crusier) and save batteries. My first thought was to use a resistor, but I'd rather use something more efficient that doesn't produce lots of heat. Maybe something like this:

uniquegoods 12V 24V 36V 48V 60V 80V DC 30A PWM Variable Speed Regulator DC Motor Speed Controller Stepless Speed Control Switch HHO Driver Module With Digital LED Display CCM6DS-D - - Amazon.com

If all goes to plan I will set it and mount it somewhere behind the glovebox. Going out of town for a bit but hope to have it all figured out in a couple of weeks.

 

[superjuice]

Yeah, PWM controller is the most efficient speed control. If you don't need the display something like this would be easier to mount and hook up.

Amazon.com: DROK DC Motor Controller 10-50V 30A 1000W PWM Step less Motor Speed Control Regulator 240HZ 2.2KHZ 22KHZ Adjustable Frequency Regulation with Switch Function: Industrial & Scientific

You have lots of options here. I have had good luck with the DROK stuff.

Here's another that's looks similar

uniquegoods 12V 24V 36V 48V 40A 2000W PWM DC Motor Speed Controller Adjustable Variable speed Switch HHO Driver - - Amazon.com

 

[bloc]

Auto AC rigs already use a transistor for blower speed control other than High. Manual AC still use a resistor pack.

What you need to do will depend on the year/model..

That said.. a DPDT relay in the circuit just before the blower motor could be used to leave the stock circuit (pos and neg) in place for normal operation, and switch the motor circuit over to your +12v and gnd for operation with the coolant heater. You could also set it up so that when the ignition is on it locks out your DPDT relay.. since if it is just thermostatically driven it'll try to do that any time the coolant is warm from driving.

Edit: hadn't read all previous posts.. @superjuice already suggested this.

I think it is your best option.

 

[superjuice]

I like the auto override function @bloc suggests, it would be easy. Just use the normally closed contacts to power the blower from your speed control. When it's energized from say the acc. position it switches to the normally open contacts. This also would keep the small current from the relay coil from draining the battery when the trucks off. I looked around the net for a waterproof/marine grade dpdt relay to no avail. If anyone has seen something please chime in. You could use two SPDT I guess.

 

[superjuice]

I like the ones with pigtails and connectors like this:

Amazon.com: 5 Pack OLS 30/40 Amp Waterproof Relay Switch Harness Set - 12V 5-Pin SPDT Automotive Relays 12 AWG Hot Wires: Automotive

 

[dan1554]

@superjuice Thanks for pointing me to that regulator for the plastic case, that is a much better option. Its on my list to purchase when I get back, along with this dpdt relay:

300XBXC1-12D Magnecraft / Schneider Electric | Mouser

I also have used these weatherproof relays in the past, pricey but they are overboard for anything I do:

Amazon.com: Fastronix 50/30 Amp Weatherproof Automotive Relay and Socket Kit: Automotive

@bloc Thanks for the auto-off suggestion. The Webasto should not send any signal to the dpdt relay when off, but if I am running the engine and heater concurrently, or if I just want to override the airflow, it would be nice to have control transferred back to the heater controls automatically.

 

[dan1554]

Some quick updates. After some research I learned about buck converters which are supposed to be more efficient than linear converters, so decided to give it a shot.

Amazon.com: Aweking Waterproof DC/DC 12V Step Down to 5V 30A 150W Voltage Buck Converter Regulator Transformer Power Supply for Car Truck Vehicle CE listed: Home Audio & Theater

The fan draws 1.2 amps at 5v. Thats less draw than a charging smartphone... Not too shabby. Runs fast enough to move a light breeze through the vents, which is perfect for my purposes.

Also made a harness with the DPDT relay. Tomorrow I should have it installed and buttoned up.