E-fan Swap Question 1993 3.0 4x4 Splash

[Coop7]

So here's what I think I'm going to go with. Might not put in the high water cut off switch yet as I don't have a good place to mount it at the moment and I'd like to have it out of the way and covered so I don't accidentally bump it.

For the A/C tie in, I suspect tying in a switched ground to pin 85 on either my high or low fan relays should do the trick depending on which speed I want activated for my A/C. I *think* I can tie it in to the switch in the truck, but without a bit more looking into it and maybe a better diagram, I'll have to hold off for a minute.

I realize 12 awg is probably over kill for some of the wiring, but it's what I've got so it's what I'm using. I intend to use 8 awg for the actual power and ground circuits as the fan should pull some amperage.

Any suggestions or mistakes you notice, please point them out.

Oh! Suggestions for a good place to tie in my +12V switched power would be appreciated. Don't really have anything in mind yet, but I suppose that's the next problem I'll be working on.

 

[Uncle Gump]

You have 86 terminal of low speed relay connected to 87a of high speed relay.

That's not gonna work...

 

[Uncle Gump]

Unless I'm missing something... wouldn't the low speed come on first?

 

[Coop7]

Unless I'm missing something... wouldn't the low speed come on first?

So I *think* that way it will only power the low speed relay until the high speed kicks on since 87a is normally closed. But once the hi temp sensor kicks on the next hi relay, that should switch power from 87a to 87 cutting the low speed relay off.

 

[Coop7]

I'll have to double check the wiring instructions on the fan, but I don't think it needs both power sources for high speed, just one for high and one for low.

And I can't take full credit for the relay setup. This is what was suggested on the volvo e fan swap write up. I just modified it a bit to fit my setup. In lieu of using the volvo combination controller, this is the dual relay system suggested. I admit to scratching my head for a bit trying to puzzle it out, but from how it looks they intended low to come on first and then shut off once high kicks on. Does that make sense Uncle Gump? Or do I need to go back to the drawing board. Lol

 

[Uncle Gump]

Ya know Coop... I remember a time when I would scratch my head for days drawing schematics from Mil Spec harness blueprints. They used these Bosch relays in some really strange ways. But that was probably 20 years ago. I also haven't dealt with schematics on a daily basis for a dozen years. So.... I'm a bit rusty.

I got thrown off because I looked at your relay sketch (in the upper right) for which you have it drawn in it's active state even though you have them marked N/O and N/C (I neglected to see that part). After a little internet refresh of my internal memory bank 87a is closed to 30 in the at rest state of the relay. So what you have drawn out should work. Provided that the low speed circuit is suppose to deactivate when the high speed circuit is active.

You also know this could be much simpler if you were dealing with a single speed fan when trying to add A/C operation. lol...

Wiring in an A/C relay in place of that low speed relay would work really well. I might even be tempted to do just that and make the low speed relay stand alone.... meaning... power the A/C relay from 87a of the high speed relay and power the 30 terminal of the low speed relay with it's own power supply (in parallel with the 30 terminal of the high speed relay).

 

[Uncle Gump]

Didn't the fan come with some sort of diagram to add A/C?

 

[Coop7]

Ya know Coop... I remember a time when I would scratch my head for days drawing schematics from Mil Spec harness blueprints. They used these Bosch relays in some really strange ways. But that was probably 20 years ago. I also haven't dealt with schematics on a daily basis for a dozen years. So.... I'm a bit rusty.

I got thrown off because I looked at your relay sketch (in the upper right) for which you have it drawn in it's active state even though you have them marked N/O and N/C (I neglected to see that part). After a little internet refresh of my internal memory bank 87a is closed to 30 in the at rest state of the relay. So what you have drawn out should work. Provided that the low speed circuit is suppose to deactivate when the high speed circuit is active.

You also know this could be much simpler if you were dealing with a single speed fan when trying to add A/C operation. lol...

Wiring in an A/C relay in place of that low speed relay would work really well. I might even be tempted to do just that and make the low speed relay stand alone.... meaning... power the A/C relay from 87a of the high speed relay and power the 30 terminal of the low speed relay with it's own power supply (in parallel with the 30 terminal of the high speed relay).

Nice! Prior service? Which branch?

Yeah, it was a bit silly of me to draw it that way. That's why I added the N/C N/O at the top. I should have drawn it in the normally closed state.

Ohhhhhh... That's a really good idea. Use the A/C switch in place of the low speed temp sender. Hmmm...

Didn't the fan come with some sort of diagram to add A/C?

I'll have to check. I would think so. I'll go dig through the box in a bit.

 

[Uncle Gump]

No military service... I worked on that while at GM... CUCV and some Hummer.

 

[RonD]

Diagram looks like it would work fine

You could add diode wire from AC Compressor 12v wire to on/off switch wire at 86
This would override switch and allow fan system to work if AC was on and temp was high enough

AC Compressor(12v wire)----------------->|---------------switch relay 86

Diode is there so turning switch on wouldn't cause AC compress to turn on

Or use yet another relay activated by AC on to ground the low speed fan relay, overriding temp ground
But fan control switch would need to be on

 

[Coop7]

No military service... I worked on that while at GM... CUCV and some Hummer.

Oof. Hummvees. Those things are a big PITA. Really easy for some things, really not for others. Lol I don't think that I've ever really gotten to take apart a civilian version? Are they pretty much the same?

Diagram looks like it would work fine

You could add diode wire from AC Compressor 12v wire to on/off switch wire at 86
This would override switch and allow fan system to work if AC was on and temp was high enough

AC Compressor(12v wire)----------------->|---------------switch relay 86

Diode is there so turning switch on wouldn't cause AC compress to turn on

Or use yet another relay activated by AC on to ground the low speed fan relay, overriding temp ground
But fan control switch would need to be on

Awesome! Good idea. I've been digging through my Haynes manual wiring diagram ( I know, I know... But it's cheaper than the stealership manual) and seeing if I can tie in somewhere in line. I hadn't considered a diode. That's a really good idea. Wondering if a diode in line on the ground side would be effective? Keep me from shorting stuff out if I tie in on that side? Just spitballing. That may not work at all, I'd have to look and see where I could potentially tie in.

I also may need to redraw my hi and low fan relay setup as they may BOTH need to be active for the high speed side. The wiring diagram provided by derale is... ok. But not great. So I've sent them an email and I'm waiting to hear back.

 

[Coop7]

Okie dokie. Just got an email back from tech support. Looks like my wiring design won't work as it needs power to both hi AND low to run hi. Not a big deal. Will redraw and see what I can come up with. Tempted to run as single hi speed setup, but then I wasted money on that fancy dual speed temp sender... Lol

 

[Coop7]

That should do it. May pick up a bus bar to tie in before the dual relays cause as of now I've got quite a bit of s... tied to one pin. Lol

In addition, I'm still a bit confused on how to tie in A/C here. I like RonD's suggestion of using a diode and tying into the positive, but as I have it set up now that still shouldn't kick on my fan unless the temp senders are at temp and grounded out. Every other diagram I have found so far with Derale fans uses the Derale control module as well, which activates the fan from +12V on pin 86 on a fan relay instead of the ground from the temp switch, but it's always on single speed fan applications. I think I have an idea of how they do it, but it would take at least one more relay, and I already have three of these damn things in my setup, four just seems excessive. Lol

My experience with diodes is somewhat slim, and with designing systems that use them I have no experience at all, which makes me a bit hesitant to design one into my system here. I *THINK* using a diode on a +12V A/C wire and tying it into pin 85 on my low temp relay ground should effectively work as an alternate ground? Since the +12V circuit would have to be completed for the AC system to actuate, meaning tying into it, even on the positive side, would give ground to pin 85 and NOT short out the system since the diode prevents current flow back to the A/C through the same connection. Does that sound right to y'all? (A/C as in air conditioning, not alternating current. Lol)

 

[Coop7]

So this^.

Sorry, I'm REALLY bad at drawing with a mouse.

 

[Uncle Gump]

Told you it would be easier with single speed.

The way it is now... A/C only turns fan on low speed. I would have it turn fan on high speed.

Also changing from pin 87a to power relay to pin 30... why not just jumper from pin 30 on the low speed relay and not high speed relay. Then just splice the 30 circuit in the harness and not actually at the connector. Cleaner and just one 30 circuit and short 87 jumper at each relay.