fan control

I am looking to control (2) 2 wire fans from the existing hi and low speed relays.

I need to turn on both fans when the computer commands either the hi or low speed.

The this is going into is a 04 SSR that had (1) 3 wire fan.

I need to insure that there is no feed back to the other relay when the fans are turned on, so that there is no feedback to the ECM.

I was thinking of adding relays to make this happen, using the pos. output that would have been sent to the fan originaly.

Help!

Thanks in Advance

Lance

Have you connected the fans in series to see if they will spin at a useable speed? 

This will only work if the fans turn at an acceptable speed when wired in series.    Also the low speed wire needs to remain hot when it switches to High speed.  If both of these criteria are met, here is your diagram.

First I think that the fans will spin slower.

Second the original fan was grounded to the chassis and only the power was switched from wire to wire from seperate relays.

The power from each pos. feed from both relays goes away!

This truck is supercharged and needs all the fan speed it can get. The fans are Spal 11" if this helps.

Yes.

Wire from battery and to fan needs to be 10 Ga or larger.  WIres connected to 85 and 86 can be smaller.  18 Ga. or so.