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'73 Cj6 Heater Blower Upgrade/thoughts/questions

Discussion in 'Intermediate CJ-5 and CJ-6 Tech' started by obarrett, Sep 25, 2018.

  1. Sep 25, 2018

    obarrett New Member

    Lake County, CA
    Sep 8, 2010
    Hi Folks,

    So... the PO did all kinds of interesting stuff to my cj6...
    - deleted the fresh air intake box assembly (just a hole from the cowl to the floorboard)
    - a DIY flat sheetmetal dash with aftermarket gauges (no wired heater controls, no factory gauges or switches)
    - no wipers
    - rewired everything... for better or worse
    - heater box thats a full of dirt/leaves, and rusted out dying motor...

    soooo, finally getting around to fixing this stuff and making sense of the wiring..

    I got a new fresh air box, hoses, defroster, wiper motor, etc... thats going well...

    The heater motor is what got me thinking...

    I read this thread about upgrading the blower model to a newer model out of a Chevy S10: heater motor swap success!

    That thread is straight forward enough if you want to go with a single speed blower, since its a single wire. I assume my blower motor is stock, and its a three wire (ground and two hots) so assume it was a 2 speed.. (PO wired a toggle switch in)

    Also found some good detail here on the same swap on a different forum, using a resistor: ECJ5

    So my questions is about the resistor...

    I am going with a blower motor out of a Chevy S10, and I want multiple speeds... should I go with the Chevy S10 resistor? or is a later model CJ/YJ resistor fine? Or can I use any resisitor made for blower motors... (even a 5 speed?)

    The resistor for the S10 w/ air conditioning has an additional terminal... would this possibly get me a 4th speed on the blower motor? What does that additional terminal for AC actually do?

    I am comfortable with the wiring the switch (and possible relay for full speed) and found a good placement for the resistor on the heater box...

    Are there any other alternatives I should explore?
    Is a 1989 S10 blower really that much better than a new 1973 OEM replacement?

    I guess I can track down a 2 speed OEM... but they looked a little pricey..

    I was probably going to grab a later model CJ7 3 way heater switch... (unless that AC resistor gives me a 4th speed) to control all this...

    Anyhow.. any thoughts would be appreciated...
    Last edited: Sep 25, 2018
  2. Sep 25, 2018

    timgr Jeepin' Nerd Sponsor 2019 Sponsor

    Medford Mass USA
    Aug 10, 2003
    As you surmised, the heater speed controls are resistors that reduce the voltage and current to the motor. Full speed is connected directly to the battery voltage, the slower speeds put a resistor in the circuit. The voltage drop in the resistor is expressed as heat, and typically the resistor is placed in the heater box so the air flow cools the element and the extra heat is added to heater output.

    I don't have a '73 TSM, but the '74 is the same in this area AFAIK. Jeep uses a 2-speed motor and no heater resistor. I presume the motor field is connected in boost/buck , similar to the wiper motor. This is shown in the TSM if you are interested, but it sounds like you are going with the 2-wire Chevy motor.

    If you use the Chevy blower motor, it seems like a good idea to copy what the GM engineers used when they built the heater. You can experiment with this stuff though, and see what works best in your application. Use you multimeter and test what resistance you get with each combination of the connections on the resistor. It's likely that the resistor was meant to work for more than one application, so it may have extra terminals that accommodate other motors or different vehicles. The wiring diagrams will tell you how they were connected in the original vehicles.

    The Jeep switch is just a 2-position toggle, so if you want the original functionality, all you need is a similar switch. If you want to restore the controls to how they looked from the factory, you may need the original switch. '73 was the first year for the infamous plastic heater controls panel, which is always broken. If I didn't care about factory appearance, I'd skip that and adapt the later in-dash controls for the heater cables. Or use something else that you like better. Not complicated. The TSM shows the heater assembly in detail.
    ojgrsoi likes this.
  3. Sep 25, 2018

    nwedgar Now with TBI!

    Newnan, Georgia
    Oct 26, 2005
    FWIW, after having the OEM box in mine, modified with a different fan motor and resistor for multiple speeds, I've come to the conclusion that it isn't worth it. I think I'm going to pull it all out and go with an aftermarket unit such as the ones I have found at Summit Racing online.

    The OEM setup is anemic, even with a new fan motor. I do get good heat at the floor now, but the windshield is nearly non-existent. I forget what motor I used because its been a few years now, but the resistor was aftermarket from a YJ if I remember correctly.
  4. Sep 25, 2018

    obarrett New Member

    Lake County, CA
    Sep 8, 2010
    thx guys... yeah, the heater control cables have been an item I have been thinking about as well...
    currently, its all hands on adjustments at the cable brackets on the heater box...
    i have the whole dash apart, and the heater box out... just need to figure out what direction i go with the blower..

    appreciate the input..
  5. Sep 26, 2018

    johneyboy03 The green beast

    Quebec, Canada
    Jan 15, 2011
    I did put a vintage air heater on my cj5. Been working nice, i'm able to change the output temp, if i want the defrost or heat to my feet.

    As for a cj6 you can stay with oem but i would like recommend to put another one at the rear just like minivan. You will have all the heat you need from there.
  6. Sep 26, 2018
    Howard Eisenhauer

    Howard Eisenhauer Super Moderator Staff Member Sponsor

    Tantallon, Nova...
    Nov 22, 2003
    nwedgar and ojgrsoi like this.
  7. Sep 30, 2018

    Raven74CJ5 New Member

    san diego,...
    Jun 13, 2018
    My father replaced the stock heater years ago in the cj5 I now have with an aftermarket unit... which replaces not just the motor but the whole heater box with core. It was a very simple and easy install... the hardest part was removing the old one that was rusted out due to the heater core leaking. He never got around to connecting all of the cables back up... I guess this will be a future project for me to look into. But the switch was mounted in dash and was a basic 4 position switch with hi mid lo and off. The heater was made by a company called Heater Craft... Ill look into it more and see if I can find a part number and post it with pictures

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