can I make my jeep electric fan run two speed with a volvo relay?

[superwade57]

So I have an electric fan from a 02 jeep grand cherokee, I believe this is a single speed fan. I also see its very common to run a factory fan relay from many volvos, they are two speed, extremely durable, and plentiful, which makes them affordable. Combine that with a single, dual temp, switch from a BMW makes a pretty bullet-proof and affordable and clean electric fan setup. My question is can I convert my single speed jeep fan to a dual speed fan using common parts and reliable techniques? I'll flush mount the jeep fan into my factory shroud, and I'm running a 355 with a large 4 core rad from a 454 suburban. I'm combining this mod with a serpentine conversion from an 89 Camaro so I'll already have the upgraded the Alt.

Wiring Gurus Unite!

Thanks in advance for your help!

[wraprail]

Thats a lot of cooling for Wisconsin. Seems kinda overkill

[superwade57]

Problem is I almost never reach temp cruising, truck is a 6 speed so rpms are pretty low on the highway with a clutch fan. Don't be fooled WI will see 90-100 pretty consistently through the summer. Plus I like to take it places. But the real issue becomes traffic. It overheats in town. It's a pretty stout 355, as can be seen near the end of this video linky....

https://youtu.be/h4qC41gRM2w

[wraprail]

That link you posted on the other thread was some interesting stuff. I guess I have been lucky, I have never had any issues cooling since I went to that ford OE fan (TBird, Taurus can't remember) and an ebay tstat and a plain old 30 amp Bosch relay. Temp goes up to around 200 in drive thru for example and you can watch the gauge drop, fan turns off. Simple setup and I never have to think about it.
The OE ford fans have the shroud molded in and really move some air compared to the aftermarket fans I have seen.

[wraprail]

Fan never comes on at highway speed. Hell this time of year it can idle for half an hour before the fan comes on.
]

[hatzie]

The 2002 Jeep fan is slowed by using a PWM speed control. If you feed it 12v it's running as fast as it's ever going to.

If the jeep fan isn't giving you enough cooling and you have no issues at highway speeds then your fan needs to move more air.

The Lincoln MK VIII fans were 2 speed units. The MK VIII shrouds are 19"x22". Rumors are that they can move 4,600 CFM... My guess is closer to 3,000 CFM. The MK VIII fan, when switched to HI, on my 2000 GMC C2500 Classic 6.5L sounds like a Cessna. It moves a LOT of air on high.

The MK VIII fan draws more on HI than a 70A F7 ISO power relay will put up with over time. I burned them out. Probably not really intended for continuous duty. The reeds and contacts are discolored in the failed units and the reed is broken. My AC clutch power was/is is set to trip the fan LO contactor. I added a 1N4007 2W diode inline to avoid the fan switch tripping the AC clutch.

When the high speed F7 relay burned up I got seriously irked and used a pair of Continuous Duty 150A 12v Golf cart contactors to run that fan motor. You can get em for $10-$15 new. Inrush current is 300A. They're weatherproof, cheap, industrial, and you will not burn them up. Hi, Lo, and Ground wires to the motor are installed with stake on ring terminals and solder. I used an ANL 100a fuse on an ANN/ANL holder. I mounted the contactors facing east and west, so the control and incoming juice studs were adjacent, and the ANL fuse on a steel plate on the LH side of the RH battery tray. ANN fuses are the same form factor as ANL but they are "Fast Acting". Motors need slow acting ANL fuses because of the startup or inrush current. ANL fuses and mounts are cheap. You could use a Bussman CB185 or similar circuit breaker. Convenient but they are more money.

The high current feed is wired directly to the RH battery. I formed a U shaped Copper buss bar for joining both contactor incoming supply studs.
The control voltage through the temp sensor is on ignition power so the key kills the fans.

If you want to allow the fans to run on LO after shutdown it can be done with a 5 terminal Mini ISO relay tripped off the ignition.
Put the HI temp wire from the thermal switch on terminal 30 (Common), the HI contactor trip wire on terminal 87a (NO), the LO contactor trip on terminal 87 (NC), and the thermal switch common terminal off the battery through a fuse rather than through the ignition. I didn't do this but if you want the fan to run after the ignition is off you'll want it on LO.

[superwade57]

To clarify hatzie, right now I'm running a clutch fan, I'm going to be switching to the serp. And electric fan in the next few weeks to prep for summer. I understand I can run the fan at 12v to get a "high" setting, I guess what I'm looking to do is run it at like 8v to create a low setting because I have such a huge rad. I'll probably never need to utilize the full 12v fan speed. So I'd like to run the low setting to turn on at like 185* at like 8v. And if I ever needed for it to run on high, kick on at like 205* with the full 12v. I know the BMW temp switch and the volvo relay will do what I need, but is there a way to run a dual lead into my jeep fan, one regulated at 8v or so and then the other allowing the full 12v?

[hatzie]

You'll either need a 2 speed fan or a PWM controller.
The Jeep fan is not a 2 speed motor.
https://www.google.com/search?q=pwm+...oller&ie=UTF-8

[SkinnyG]

GM recalled a ton of Cavaliers/Sunfires because they take so long to start while cranking, that they would catch fire and burn to the ground. You can get a killer relay from the recall from any Cavalier/Sunfire in the wreckers.

[superwade57]

Originally Posted by SkinnyG

GM recalled a ton of Cavaliers/Sunfires because they take so long to start while cranking, that they would catch fire and burn to the ground. You can get a killer relay from the recall from any Cavalier/Sunfire in the wreckers.

An electric fan relay? What are the specs on it? Is it also a pulse width mod. Or just a relay?

[SkinnyG]

No, it's just a relay, but big enough for the starter on a Cavalier. Your fan switch will trigger it, and the relay will connect the current to it. It's just a big, cheap, plentiful, relay at the wreckers.

[mcmlxix]

I have a 2 speed fan from a Jeep Grand Cherokee... I thing it was an 04 with HD tow package. Its a true two wire fan with two separate windings.. It fit perfectly into my 72 SBC fan shroud... Not sure about 73+

[Rich84]

I do not understand why you would want to run a "slow speed" fan. Just get a thermostat and a fan controller set at the proper temps and let them do their job. The faster the better. I have a 180 thermostat and the fan set to come on at 195. Fan rarely turns on unless in traffic. I can watch the gauge go back to operating temperature.
I don't think low voltage would be good for an electric motor. It kills our power tools.

[hatzie]

Dual motor winding 2 speed fans, like my Lincoln MK VIII fan, draw a lot less current on low speed.

PWM control and a resistor to lower the voltage are two very different animals. PWM is outputting a square wave pulse at 12v amplitude that is literally turning the fan on and off at lower speeds but still at full rated voltage. A resistor cuts the voltage down by wasting power as heat. Cutting the voltage will damage a motor. PWM control will not.

I do agree it's better to just run the fan and have done with it. His cooling issue may simply be a missing shroud.

[Rich84]

Hatzie, Running an electric fan all the time would probably shorten it's life quite a bit as well..No?

[hatzie]

Originally Posted by Rich84

Hatzie, Running an electric fan all the time would probably shorten it's life quite a bit as well..No?

I never said to run it 100% of the time and neither did the OP. I have a pair of thermal switches on my GMC. 190F and 210F. It almost never runs on HI and not that often on LO. That MK VIII fan moves an insane amount of air even on low. His proposed setup is the BMW dual thermoswitch.

The OEM and Aftermarket PWM controllers typically turn low speed on at 180-190F and ramp up the speed if the temp doesn't drop.

[hatzie]

Originally Posted by SkinnyG

No, it's just a relay, but big enough for the starter on a Cavalier. Your fan switch will trigger it, and the relay will connect the current to it. It's just a big, cheap, plentiful, relay at the wreckers.

Those are just Metripack 630 Mini ISO relays in the 18ga wire on the control side of the starter solenoid. 30A at most probably more like 20A.

The reason they used them is to isolate the BCM or anti theft module output that controls starter cranking. Controlling the starter using the BCM is part of the theft deterrent system...