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Electrical Question

Discussion in 'Early CJ5 and CJ6 Tech' started by linckeil, Mar 27, 2006.

  1. linckeil

    linckeil Member

    I have a heater fan motor with relay from a 1991 Chevy Blazer that I'm going to stuff into my stock jeep heater box. The stock jeep fan motor has a high and low speed, but the blazer motor is a single speed.

    It would be a peice of cake to wire it as a single high speed, but I'd like to have at least a high and low setting. Obviously this is possible as the Blazer had a 4 speed setting. My question is, How? Is there some kind of switch I can wire in that would provide differing resistences when set to different speeds? Any websites or books out there that someone can direct me to?

    Thanks.
     
    linckeil, Mar 27, 2006
    #1
  2. jd7

    jd7 Sponsor

    Napa used to list several types like that in their books
     
    jd7, Mar 27, 2006
    #2
  3. AKCJ

    AKCJ Active Member

    Yes. I got a two speed pull switch from NAPA and it had the built in resister for low speed. It even has a built in fuse. And it was low $!
     
    AKCJ, Mar 28, 2006
    #3
  4. timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Resistors dissipate a lot of heat ... I would use an SCR and turn it on and off at different rates to get a change in voltage. However, I'm fairly proficient with electronics stuff...
     
    timgr, Mar 28, 2006
    #4
  5. jpflat2a

    jpflat2a what's that noise?

    which is why the factory resistor pack is mounted thru the housing; when fan is on, air blows onto the resistors....
     
    jpflat2a, Mar 28, 2006
    #5
  6. Howard Eisenhauer

    Howard Eisenhauer Administrator Staff Member


    O.K., I'll bite- Assuming we're operating @ 12V DC once you turn the SCR on, How are we turning it Off again ??? :)

    Enquiring Minds Want To Know-

    H.

    p.s. What kinda filter are we using to keep da hash outta da HI FI ?
     
    Howard Eisenhauer, Mar 28, 2006
    #6
  7. timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    I'd charge a capacitor for the timing (RC circuit). There are lots of ways to generate a square wave at a specific frequency. Simplest I can think of is a flip-flop that alternately charges/decharges the cap. Model train controllers use this kind of a circuit to start locomotives slowly.

    Re the rf interference, put it in a box and use a Corcom-style line filter on the outputs.

    Not complicated in toto, but putting the resistors in the air flow (per Jim's post) would be simpler and cheaper.
     
    timgr, Mar 29, 2006
    #7
  8. 65CJ5

    65CJ5 Member

    I have some info on my site that might help you:

    http://home.comcast.net/~sday77/binky/index.htm

    Go to the repair section and look at the heater motor stuff. I used some big ceramic resistors that worked OK. SCR would be neat. Anyone have a schematic for that?

    Stan
     
    65CJ5, Mar 30, 2006
    #8
  9. timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    I don't have a schematic, but one source on the web suggested a speed control from a junked cordless drill. That's an SCR circuit. Other than that, I'd hit the books and look for a DC motor control circuit that I could adapt.
     
    timgr, Mar 30, 2006
    #9
  10. linckeil

    linckeil Member

    Thanks for all the info guys. And 65CJ5, you got a great site. Once I read your heater motor upgrade, I'll be sure to check out your other writeups.
     
    linckeil, Mar 30, 2006
    #10