68 GS400 - new blower motor not coming on

Discussion in 'Sparky's corner' started by cardave, Nov 3, 2019.

  1. cardave

    cardave Active Member

    I currently have the R/F fender off the car and installed a new Delco blower motor (made in Canada).
    Testing - I ran a wire from the blower motor to the + positive battery terminal, then ran a ground wire from one of the blower motor attaching bolts to the - negative battery terminal. Blower motor is working!

    Next, tried various blower speed settings and then took test light to the blower motor terminal, verified I have power to the motor, as well as each resistor tab, but blower won't turn on. Took my test light to the extra non factory ground wire that was attached to one of the blower mounting screws, and verified that power was coming to it with ignition switch on. Touched it to ground and still no blower motor working.

    Removed negative battery cable, cleaned the ground end. Took off ground wire from VR to back of cylinder head, cleaned and tightened as well.

    Could the issue be in the blower switch? Does the system ground through it as well?

    Thanks,
    Dave
     
  2. BuickV8Mike

    BuickV8Mike SD Buick Fan

    Or as likely the circuity in between. Do you have a voltmeter?
     
  3. cardave

    cardave Active Member

    BuickV8Mike - thanks for the quick response. No, I need to buy a new one as the old one is broken. Are you thinking I need to see 12 volts at the blower motor connection?

    Since my last post, I went out, turned ignition to on, selected medium speed, this time connected a jump wire to the small ground wire off the negative cable AND hooked up my extra ground wire from one of the blower motor attaching bolts and the blower came on. Selected a different speed, and the blower didn't seem to change to a different speed.

    So my questions are:
    -Do all roads lead to a bad switch?....considering blower motor (Delco brand) and resistor (The Parts Place) are brand new.
    -Why do I have to ground the blower motor? The FSM indicates it's self grounding.
    -Should there be another ground from block to frame considering there is only one from block to firewall?
     
  4. BuickV8Mike

    BuickV8Mike SD Buick Fan

    My guess is the switch is good but the wire doesn't have 12 volts to the fan motor.
     
  5. BuickV8Mike

    BuickV8Mike SD Buick Fan

    The fan frame should be the ground. Check the + 12 wire with a bulb.
     
  6. cardave

    cardave Active Member

    @BuickV8Mike - sorry to sound dense here, but does + 12 wire mean "positive 12 gauge wire" to the blower, which is the black/orange wire?
    I will do that per your advice. Any thoughts on why the motor isn't self grounding?
     
  7. cardave

    cardave Active Member

  8. BuickV8Mike

    BuickV8Mike SD Buick Fan

    Dave, this doesn't seem correct. The ground should not be hot (+12 volts). I also think the 72 wiring would be the same. Are you saying the switch works the motor with an additional ground attached?
     
  9. cardave

    cardave Active Member

    Yes, the extra ground wire bolted up to one of the mounting screws for the blower motor, lights up my test light! You can touch any of the 4 screws with a test light and they light up. FYI, I do have a new multi meter on it's way.
     
  10. BuickV8Mike

    BuickV8Mike SD Buick Fan

    Sounds to me like thats the problem. If the fan get 12 volts but the ground has 12 volts NOT zero there is no voltage difference. Does the lighter work on the dash and does the dash light the test light?
     
  11. cardave

    cardave Active Member

    UPDATE, it's fixed! Thank you BuickV8Mike for your advice.

    Just wanted to update this thread to let everyone know I finally got the problem solved. Having a new blower motor in place along with a new resistor and still no fan speeds, I decided to purchase a NOS switch. Got that installed and still nothing! New volt meter had just arrived so with the car running, I started at the switch and had 13.5 volts, next stop was the resistor, 13.5 as well, next stop was the end connection of the harness before it plugs into a short piece of wiring that connects to the blower motor. Again 13.5 there as well. I decided to disconnect the short piece of wire from the main connection and all of a sudden realized that the wire connector had somehow come off of the blower motor! Good Grief!

    After removing the R/F fender part way, I put a new connector on the wire end that connects to the blower and reassembled the fender back on the car. I go to turn on the blower, hear the fan running, then everything stops. Turns out someone has put a 15 amp fuse in place where a 25 amp should be. After that all is good!

    Am now ready to recharge the A/C and keeping my fingers crossed.......
     
  12. cardave

    cardave Active Member

    Forgot to mention:

    Regarding the blower motor ground wire. The blower motor DOES NOT just ground through the mounting. I have an FSM and stumbled across a picture of the firewall and it is showing a small short ground wire attaching to the firewall on one end and the other end attaching to one of the mounting nuts for the blower motor.

    Looking back, this is such a simple setup from switch to blower motor, but it kept my head spinning for a couple of months. Not to mention how much of the dash you have to remove to change the blower switch on a '68. I took the old switch apart and it didn't look back, but didnt have some dirt/dust/gunk on the inside where the contacts rub.
     

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