1998 S70 Cooling Fan Hard-wire; bypass relay

Post by **kickin_it** » 20 Sep 2014, 18:31

I have a high mileage s70 I am just trying to keep alive. My cooling fan relay is shot and it looks like the wires were also cut by the fan or some outside force. My question is if there is anyway to hardwire the fan to run only when the motor is on. I do not want to replace the relay, I want to bypass it. I don't mind the noise of the fan but I also do not want to have it running when the car is off for obvious reasons. I just need it to get me to work and back 15 min away. It does not overheat unless the car is run hard for a longer time or stationary for about 10 minutes. Any diagrams or photos of a possible fix would be greatly appreciated. Thanks.

Post by **tryingbe** » 20 Sep 2014, 22:57

Why not just replace the relay and fix the wiring. It'll be cheaper and easier.

Other wise, you're looking to add wiring, adding relay, finding an ignition on wire, splicing into that wire to new relay and add more wiring...

Why would you want to go thru all that when you can just fix the existing wiring and replace the relay.

Post by **BEJinFbk** » 21 Sep 2014, 00:24

+1
Fixing it correctly will not only be easier,
it'll save any future owner the trouble of
figuring out the hack and making it right.

Post by **kickin_it** » 23 Sep 2014, 21:15

This car will not have a future owner, believe me. Not really what I asked for but thanks for the opinions anyways.

Post by **Ozark Lee** » 23 Sep 2014, 21:38

The problem is that you really can't just tap a slot in the fuse box for the engine cooling fan and expect for it to work for very long. The fan relay supply has a fusible link, directly tied to the battery, that is rated for 60 Amps. The B+ line on these cars is pretty weak to begin with and taking on that much more current draw to the fuse box might significantly hasten the car's ultimate demise.

It would be easy enough to use either the yellow or the yellow/white wire to trigger a relay (the triggering is done by those wires going to -) and then tie the relay output to either the red or the green wire on the fan. It all depends on what speed you want the fan to run at.

...Lee

Post by **BEJinFbk** » 23 Sep 2014, 22:39

We're talking about a 60 amp relay here.
These aren't just laying around like a 30 amp
bosch SPDT 5 pin. Might as well just fix it.

Bad relay? Hit the junk yard. It doesn't have
to be expensive to fix it "right". And at the
end of the day, it WILL be easier.

Post by **tryingbe** » 24 Sep 2014, 02:05

kickin_it wrote:Not really what I asked for but thanks for the opinions anyways.

If you want to put more work into it and do it the way you want, by all means, do it.

I've added Volvo fan to my Dodge Daytona, Dodge GLH, Shelby CSX, and a Volvo 240. You would think my opinion would count heavily.

Daytona install

CSX install

GLH install, custom shroud

Post by **phils94850** » 24 Sep 2014, 06:57

turbo dodge.. ive had a few of those...

Post by **jimmy57** » 24 Sep 2014, 07:24

IF you have a pick n pull type JY near you the relay will be cheap and you can cut the harness to get some wires for repair. The wires that failed I would assume are the two small gauge relay trigger wires. Those can be installed back onto relay even when the plastic molded stuff fails and the wires no longer stayed put in the connector.
The cooling fan relay is the same for 850, 92 and later 940/740/960/s90/v90 so the models you could pluck one from is pretty wide.
You will not find a switch that will handle the fan load for cheap so you would likely spend more money rigging around the std setup than you will at a pick n pull.

richardgengle · Post by **richardgengle** » 02 Jan 2022, 18:50

could i connect the fan's purple wire to battery hot or ground ... or maybe to the alternator [thinking it would only have voltage when engine is turning?]

i ask this because the fan only seems to work if i reverse polarity to the 2 big wires.