Bosch dual relay setup.

[brentmc]

I don't know if I have this in the right place or not. Mods feel free to move. Anyway I was looking at the tech pages at the diy dual bosch relay setup for the Taurus fan mod. I noticed on the high speed relay the 86 pin ties into the 87 pin. Shouldn't that tie into a switched 12+ power supply instead?

 

[RonD]

Yes, that does look like a mistake in the diagram.

Diagram is the last one on this page: http://www.therangerstation.com/tech_library/volvo_electric_fan.shtml

"Home made" dual speed relay
High speed relay on the left has jumper from 86(coil) to 87(load), this is incorrect
Jumper should be from 86(coil) to 30(12v)

It doesn't need to be a switched 12volt source since the relay is the switch, the temp sensor is the ground controlling the switch.

As drawn now the high speed circuit wouldn't come on.

 

[brentmc]

True about not needing a keyed switch. I just don't think that the high speed of the fan needs to run after I shut off the engine. According to the diagram the low speed side is wired live the whole time and it'll run till the engine had cooled down.

 

[RonD]

Shouldn't need E-fan to run after engine is off, belt driven fan doesn't.
On vehicles designed and built with E-Fan they often have fan(s) stay on after key is off, this is usually because of smaller profile of rad in transverse mounted engine setups, Ranger retro fit wouldn't need that.
If some one wanted that option then I would add a timer circuit, since rad hose temp sensor wouldn't work well without water pump circulation, natural cooling would eventually shut off fan, but...........kind of an open ended process as far as time, with no real benefit.

One of the available options after E-Fan is installed on a 4x4 is the ability to shut off the fan when water crossings are done, so upper engine compartment can stay drier, i.e. no water being sprayed by fan blades.
So having a manual switch/relay to disable e-fan would be a option to look at.

 

[Jim Oaks]

Ok. I'll work on making a new diagram.

 

[Jim Oaks]

Changed it:

Better?

 

[RonD]

Yup, looks good.

High speed relay is passing 12v power to low speed relay coil(86) via 87A
So when low temp switch grounds out(85) the low speed fan gets power
If high temp switch grounds out High speed relay closes cutting power to low speed relay, and powering up high speed fan