Offline 1969cadillac

  • Posts: 124
  • Name: murray mules

I am adapting a latter model air pump to suit my 69 series 75 limo....

problem is I don't know how to hook up the electrical or vac side of things .... nothing is marked !

Q. in pic 4 the terminal is loose ... but what is it an earth or power terminal ??

Q. there is a 2 pin connector on top of the pump .... how to connect

Q. in pic 5 there is a Schrader valve .... is this to test pressure ?

Q. in pic 6 there is an outlet on the tank.... is this to connect to the air lines ??

thankyou , Murray Mules

Offline TJ Hopland

  • Posts: 6823
« Reply #1 on: June 12, 2017, 08:53:02 AM »
The single electrical connector is to the motor.   Body is the ground.    The 2 pin connector is the vent solenoid, one ground one plus.   The outlet is on the 'tank'.   Its not really a tank, its just the housing for the drying media. 

The way these worked was there was a control module connected to an electrical level sensor.  The module then decided if the level needed to be changed or if it was just a transient condition that didn't require adjustment.    If the module decided the car was low it would activate a relay which would then power the pump motor which would raise system pressure which would raise the car.  When the car was at the proper height it would turn off the relay/motor.    Similar if it was too high, module sends power to the vent solenoid on the motor which bleeds off system pressure. 

The way the old system worked was more like a home air compressor.   The compressor was kind of a stand alone unit that just maintained tank pressure.   It didn't know or care what was going on with the rest of the system,  it just knew tank was full or not.  If it wasn't full it worked to fill it.     Tank was connected to the level sensor at the back axle.    The level sensor was a valve assembly with a damping mechanism in it.  Car goes low valve shifts and connects tank pressure to the shocks which raises the car.   Car goes high valve shifts to vent off some pressure.   

I think the option I would try would be to get a small air tank and a pressure switch connected to the new compressor so it works like the old one,  it just maintains pressure.    The rest of the system should not know the difference. 

If you don't go that route then you will have to either be fully manual and rig up a up/down switch that will either operate the motor or the solenoid or you will have to find and wire up an original level sensor and control module.   The modules didn't appear to be especially reliable and were difficult to repair. 
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
75 Eldo rusty but trusty
80 Eldo Diesel
And other assorted stuff I keep buying for some reason

Offline James Landi

  • Posts: 688
  • 2007 XLR
    • CLC Member
      CLC Member #21920
  • Name: James Landi
« Reply #2 on: June 13, 2017, 12:18:50 AM »
TJ's explanation is spot on--- and he is assuming that your old level controller is still on the chassis with its arm still attached to the rear axle. Assuming that he is correct in his assumption, his adapting "device" seems like a good idea... your new pressure pump world pressurize a separate small air tank that would have three places for fittings.  One would be from your new pump, another would be the output to your rear level controller and the other would be an air pressure actuated switch that you'd electrically connect  through the battery and would actuate the electric pump when the internal pressure in your new little tank drops below 80 psi.  Another approach would have you find a load level device from an 80's Cadillac that electrically "matches" your pressure motor and run the pump off that that device.  The only other part that you'd need to purchase is an electric relay that will connect your pump to the car battery and would "trigger the relay from the low amperage switch built into the rear axle controller.

The simple "work around" would have you connect your new electric pump directly to your air shocks and have you "act" as the controller of the level height by way of a heavy duty "momentary on" button with the switch in the car.  If you connected your pressure "output" through a "Tee" you could mount a pressure gauge next to the momentary switch and simply adjust the height by monitoring the gauge pressure.  I've done this as a "work around" on one of my Cadillacs, and eliminated the height adjuster, substituted a tee at the rear for the shocks... I found that I rather enjoyed having the rear end of the car somewhat higher.  It also helped with rear visibility.   


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