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Adding Lumbar to '69-70 Mach 1 Seats

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This past Spring & Fall, I rebuilt my Mach 1 Seats using new foam, springs, burlap, and felt.   At the same time, I added Rostra Rear Mount Power Lumbar kits (250-1453).   These kits come with 3-way momentary switches to pump up the lumbar bag and deflate it.   Normally you would mount these switches in the side plastic trim of a modern car seat … something absent from a classic Mustang Seat.   Not being able to think up a simple solution to this I instead modified the switch harness extending it to above the radio to use the two empty switch spots there and used two standard SPDT momentary 3-way toggle switches for a 1/2" hole.

Problem is, the Rostra Lumbar switches are not normal ON OFF ON, instead the "inflate" direction energizes both the pump and the dump valve and the "deflate" direction energizes only the dump valve.   So, since my std. switches only energize one or the other, the pump will run but not inflate the lumbar bag.

Even though I can't wrap my head around HOW this Rostra circuit can possibly work this way, I've figured out how to duplicate the Rostra Switch circuit using DPDT switches and two jumper wires per switch instead of the SPDT that I have in there now.

Question for you electrical gurus … I was also wondering if I could just add a Diode of some sort between the two switch terminals that would allow current in the one direction but not the other.   The circuit uses a 5 AMP fuse, so I'd guess the Diode would need to be good for 5A.   I would think you could even add this Diode at the pump which would not require me to remove the whole dash pad, etc. again to get to my switches.   If this will indeed work, can someone recommend a part number of what I need to order ?? 

I did write-up with lots of pics on my seat rebuild / lumbar install … see attachment.

Thanks,

Doug

 

          

Rebuilding 69-70 Mach 1 Front Seats.pdf

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I can maybe help you out, but I will need more information.  I need to know more about these wires.  How many wires does the Rostra system have,  and where to the wires connect?  It looks like the pump has one harness to the switch, and probably another wire to the +12v, and one last wire to ground?  Is this the case?   How many wires go to the switch? 

It would seem to me that the Rostra switch is a On-Off-On momentary contact switch, just like the switch used for convertibles that goes in  the same location.   You should be able to use any On-Off-On switch and connect the wires the same way the rostra switch is connected.

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Ground Wire runs to pump motor & dump valve.

Power Wire runs thru 5A Fuse then to switch

Two wires from switch go to positive motor & dump valve 

Switch is a momentary 3-way switch, however it powers BOTH the pump motor & dump valve wires when you want to ADD air to bladder then just the dump valve when you want to remove air from the bladder.

I have normal 3-way SPDT momentary switches in there now, but being normal they only power either the pump or the dump valve.   If you power just the pump, it runs but you get "0" air out of the hose.  

As I said in my 1st post, how this actually works has me sort of baffled.   I'm a hydraulic/pneumatics guy and to me this should be a simple energize the pump to inflate and energize the dump valve to deflate.   My curiosity got the best of me so I pulled the pump assy. out of the padded pouch it comes in to see if that helped me make sense of it.   Pump does run through the dump valve, so maybe instead of being a single check in the dump valve to hold air in the bladder (which would allow the pump to pump air through it while de-energized) it is some sort of double check in this valve which would require it to be energized with the pump.   And being in series with the pump, it actually bleeds bladder down backwards through pump when just the dump solenoid is energized.

Pic of pump / dump valve assy:

1744096971_PumpDumpValve1.thumb.JPG.e4c90054c17a4c3319d848ef4551a1f8.JPG

     

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If you look at the pic you have posted the yellow wire goes to a dump valve which lets the air out without the pump running the green wire goes to the pump and energises the pump but not the dump valve. 12v supply from the accessory side through a 5amp fuse. The black wire is ground.

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Nice write-up, now I'm going to have to do it dang nab it! There are various ways to deal with this. The attached PDF will show you two. Personally I would go with the top one. It uses a single switch like this: https://www.zoro.com/honeywell-toggle-switch-dpdt-10a-277v-screw-12ts15-7/i/G4674092/feature-product?gclid=EAIaIQobChMIiO7msZjA3wIVjqOzCh28eAfMEAQYASABEgICWfD_BwE.

The lower one uses a diode like you suggested, but it only drives the valve with forward current. You wouldn't want to make it 5A because that would be a honking big diode, so you would need to put an ammeter on the valve and see how much current it uses- when the alternator is charging (that raises the voltage and current goes up with it).

 

LUMBAR CIRCUIT.pdf

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9 minutes ago, unilec said:

Do you have a wiring diagram for the switch?

If you are referring to me, then YES- its in the above attached pdf called "LUMBAR CIRCUIT".

No offense, most people have a difficult time with electrical stuff. Can you open it and identify the DPDT switch? Its the six dots and two levers just to the right of B+. Maybe I should have drawn a border around the switch. Does this help- see attached

lumbar2.pdf

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Yes, either the DPDT switch or the diode idea will work.  The diode might be easier, because you already have the swtiches.  Something like a  6A10T from Diodes Inc.  It is available from DigiKey for 47 cents each.  it is a 6 amp part, that will work fine for you.   The link is below.

https://www.digikey.com/products/en/discrete-semiconductor-products/diodes-rectifiers-single/280?k=6a10t&k=&pkeyword=6a10t&sv=0&v=31&sf=0&FV=ffe00118&quantity=2&ColumnSort=0&page=1&pageSize=25

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48 minutes ago, danno said:

Yes, either the DPDT switch or the diode idea will work.  The diode might be easier, because you already have the swtiches.  Something like a  6A10T from Diodes Inc.  It is available from DigiKey for 47 cents each.  it is a 6 amp part, that will work fine for you.   The link is below.

https://www.digikey.com/products/en/discrete-semiconductor-products/diodes-rectifiers-single/280?k=6a10t&k=&pkeyword=6a10t&sv=0&v=31&sf=0&FV=ffe00118&quantity=2&ColumnSort=0&page=1&pageSize=25

Interesting, I did a search on Digikey earlier today and didn't find anything available- all were obsolete. Guess I'll have to tweak those search parameters differently next time. The only good thing about a single switch is just that- its a single switch, and nothing else is needed.

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Here is a pdf of the Rostra Circuit & troubleshooting page … no switch detail in the drawing, just an explanation how to test /troubleshoot the switch at the bottom of the page stating both sides are powered when switched to "inflate".

I also scribbled up a quick sketch of how I would wire up a std. DPDT switch.

Thanks DANNO on finding a Diode that will work … that route looks good and easy too.

Thanks,

Doug

DPDT Lumbar Switch Circuit.JPG

Rostra Lumbar Circuit & T-S.pdf

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