Wire Fan to A/C Switch

[art1029]

1993, MT, 2WD

Need some help from the guys that have added the dual speed electric Volvo fan to your Ranger. How do you wire the fan to turn on when the A/C is turned on?

Right now I have it set to turn on with a temp sensor in the upper radiator hose. When the A/C is on before the truck to warm enough, the condenser will get too hot and the high pressure A/C hose will get too hot and push all the freon out.

My thought is that I wire one speed to the temp sensor in the upper radiator hose and then second speed fan to the A/C switch. You think this will work?

 

[RonD]

No, that won't work

The Volvo temp switch is a Ground control switch
It has a ground wire, then 2 ground wires out, one for low speed relay and the other for high speed relay
As the switch warms up it grounds the low speed wire
If switch gets hot enough it grounds the high speed wire


AC clutch control is 12volt, so can't be hook up directly to ground wires

You will need to add a relay, activated by the 12v going to AC Clutch
The relay would then Ground either the low speed wire or high speed wire on the switch, your choice

Standard automotive relay looks like this: https://www.gtsparkplugs.com/images/mini-automotive-relay-wiring-840x.jpg

85 and 86 are used to activate the relay
30 and 87 are then connected when relay is activated

So run a ground wire to 85 and 30, they share the same wire
Then AC Clutch 12v wire to 86, to activate the relay
Then 87 will connected to either the low or high wire, spliced

When AC is on one of the temp switch's ground wires will be grounded thru the relay, so fan on
When AC is off temp switch still controls the fan for both speeds


Heads up on upper rad hose temp switches
Make sure the switch is on the side or lower part of the hose as these temp switches can only read fluid temp, not Air Temp
So if system gets low on coolant/fluid then fan can shut off if switch no longer has fluid flowing past it

 

[97Ranger3.0]

No, that won't work

The Volvo temp switch is a Ground control switch
It has a ground wire, then 2 ground wires out, one for low speed relay and the other for high speed relay
As the switch warms up it grounds the low speed wire
If switch gets hot enough it grounds the high speed wire


AC clutch control is 12volt, so can't be hook up directly to ground wires

You will need to add a relay, activated by the 12v going to AC Clutch
The relay would then Ground either the low speed wire or high speed wire on the switch, your choice

Standard automotive relay looks like this: https://www.gtsparkplugs.com/images/mini-automotive-relay-wiring-840x.jpg

85 and 86 are used to activate the relay
30 and 87 are then connected when relay is activated

So run a ground wire to 85 and 30, they share the same wire
Then AC Clutch 12v wire to 86, to activate the relay
Then 87 will connected to either the low or high wire, spliced

When AC is on one of the temp switch's ground wires will be grounded thru the relay, so fan on
When AC is off temp switch still controls the fan for both speeds


Heads up on upper rad hose temp switches
Make sure the switch is on the side or lower part of the hose as these temp switches can only read fluid temp, not Air Temp
So if system gets low on coolant/fluid then fan can shut off if switch no longer has fluid flowing past it

Would this be an accurate diagram based on how you described it?

The only thing I changed is I used the A/C relay to bypass the temperature switch when activated. The reason being, I'd imagine you wouldn't want the possibility of the A/C relay activating the High side of the fan motor and the temperature switch activating the Low side simultaneously. Or would that not matter?

 

[RonD]

No

Here is how to wire the Volvo fan unit IF..........you want a switch in the cab OR key on only Fan

https://www.therangerstation.com/tech_library/images/volvo_relay_diagram.PNG

Other wise you do not need the relay, just fused power to Volvo relay 30
Now if the engine was hot when you shut it off the fan will continue to run until coolant temp is under low speed temp setting
Many vehicles have it set up that way
If you are worried about the battery draining then used the relay with key on power

So in your diagram "12v all" would be key on 12v or switch in cab on/off 12volt(although I would use the ground, 85, to a switch in the cab, just need 1 wire that way, whole cab is a ground, lol)



AC side is separate
Its relay is grounded, 85
12v from AC clutch , 86
30 ground
87 to Temp switch high
Nothing on 87A

The Volvo relay set up only powers low speed or high speed fan wires, that is all done inside the relays
i.e. the coolant heats up and low speed wire is grounded, if coolant gets hotter then high speed wire is also grounded, but low speed is still grounded, so if it cools off low speed power comes back when high speed power is off

AC relay will ground high speed or sensor will, doesn't matter, to activate the high speed fan
It will do that whether or not low was on or high was already on

I would wire to the low speed wire, because fan will come on with AC on even when engine is cold, also in winter when using Defrost
High speed will come on if coolant gets hot enough, so you don't really need AC to go directly to High speed, in my opinion

 

[97Ranger3.0]

No

Here is how to wire the Volvo fan unit IF..........you want a switch in the cab OR key on only Fan

https://www.therangerstation.com/tech_library/images/volvo_relay_diagram.PNG

Other wise you do not need the relay, just fused power to Volvo relay 30
Now if the engine was hot when you shut it off the fan will continue to run until coolant temp is under low speed temp setting
Many vehicles have it set up that way
If you are worried about the battery draining then used the relay with key on power

So in your diagram "12v all" would be key on 12v or switch in cab on/off 12volt(although I would use the ground, 85, to a switch in the cab, just need 1 wire that way, whole cab is a ground, lol)



AC side is separate
Its relay is grounded, 85
12v from AC clutch , 86
30 ground
87 to Temp switch high
Nothing on 87A

The Volvo relay set up only powers low speed or high speed fan wires, that is all done inside the relays
i.e. the coolant heats up and low speed wire is grounded, if coolant gets hotter then high speed wire is also grounded, but low speed is still grounded, so if it cools off low speed power comes back when high speed power is off

AC relay will ground high speed or sensor will, doesn't matter, to activate the high speed fan
It will do that whether or not low was on or high was already on

I would wire to the low speed wire, because fan will come on with AC on even when engine is cold, also in winter when using Defrost
High speed will come on if coolant gets hot enough, so you don't really need AC to go directly to High speed, in my opinion

Sorry, my handwriting is bad, what looks like 12V ALL is 12V ACC - like you had said I added that relay so that the fan would only come on with the key on.

Thanks for the clarification on the temp switch - I didn't realize the switch would ground both at the same time when the temp gets hot enough to activate the high side. But looking at this other diagram from that article I understand now why that isn't a concern, since it's setup to where both relays are not activated at the same time even if both are grounded.

 

[97Ranger3.0]

When it comes to wiring I'm very visual and need to draw it out lol. So would this be correct? The main relay is optional for power only when the key is on, or just go straight fused from the battery as you said. And the A/C relay 87 wire could splice into either low or high.

 

[RonD]

Perfect

 

[85_Ranger4x4]

I used a four relay block off of amazon. On my truck the efan switch is a ground and the dash switch to the A/C compressor is 12v, so I wired it so either way it would ground the two relays for my dual fans (each fan has its own relay too)

'85 Ranger Restomod

Well anyway it did funeral stuff without missing a beat: Been driving it and I think everything is going to stay together. Header collector leak persists but it is the side I am going to redo so it can just have a good time while it can. So one thing I want to do is get the front efans to...

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