I hate the inefficiency of a mechanical fan. Even with a fan clutch, it's a drag on the engine. Also every time I'd get on the gas I could hear it. Chrysler has a technical service bulletin on replacing it with a quieter one but I think it's the equivalent of putting perfume on a turd.

A turbo Mopar friend of mine who is also into turbo Volvos turned me onto Volvo’s 2 speed fans. It comes in the FWD cars. This thing on high moves some air! I put one in my Dad's 2.2 turbo '85 Chrysler T&C wagon because it has the smaller radiator to accommodate the intercooler. It solved his running hot in the Arizona summer problem. The best part about the Volvo fan, is if you can find the right one, the fan shroud is almost flat and you can adapt it to almost any radiator. If you do get a Volvo fan from a junk yard, get the relay block and wiring that plugs into it. There are four wires to wire up: battery positive, battery negative, and one ground wire for each speed.

The fan:



The fan fit the radiator almost perfect. It did fit perfect between the tanks. I had to build a couple of straps to hold it in place. I used the factory holes in the radiator incase I ever have to replace a radiator on the road. I'll have sockets and wrenches with me but not a drill. I had to flip the fan upside down because it would have hit the water pump. In doing that, the flaps in the shroud are now upside down and wouldn't stay closed. So I had to drill new holes so I could hang the flap down.





Fan control:

We all know that with a mechanical fan, the computer doesn't control the fan on/off schedule. So what to do on the cheap? I worked at an import shop for a awhile. I know that '90's Honda's have a temp sensor to turn the fan on and off, not the computer. So I went to the junkyard and snagged a couple of these switches and plugs. The switch opens at 200* and closes at 190*. Now, where to put it? Anybody who has done a thermostat knows there’s no room on the intake for an additional coolant sensor and if it was a Chevy we'd have an extra port on the head. Well, coolant is always flowing to the heater core and it's right off the intake next to the coolant temp sensor. So I went to ACE and bought some brass fittings to extend the hose barb for the heater core and bought a T for the Honda temp switch. The Honda temp switch threads are 16mm and the brass T is 3/8" pipe thread. I bought a 3/8" to 1/2" pipe thread reducer to adapt the Honda switch to the brass T. 16mm X 1.5 and 1/2" NPT are so close and the Honda temp switch has an o-ring I was able to screw them together and snug it down. I got lucky.

Before:



After:



What to do with the low speed of the 2 speed fan:

Before I opened my own shop, I worked out of my garage at home and used my mini-van to run for parts. I had a switch in my van to manually turn the fan on before I got to where I was going. Most of the time I'd forget, park the van with the engine at 210*, come out and the temp spiked up to 230*, and by the time I got home the temp is still at 210*. So I wanted a timed switch so I can run the fan after I shut the vehicle down to cool things down and I don't have to come back out to shut it off, or come out to a dead battery. I discovered that the factory rear window defrost switch has a nine minute timer. I don't need a rear window defroster in Arizona. So I wired my switch to turn the fan on after I shut the vehicle down, and nine minutes later it shuts itself off. So I decided to do the same thing in my Dakota. But there is no defrost switch. I grabed one out of an early ‘90’s Dodge Spirit. It even has holes to mount it. It almost looks factory.



With a 180* thermostat and a huge radiator, the fan hardly ever comes on. Unless I turn the A/C on. It’s wired to come on with the a/c compressor. The fan from the junkyard cost me $16, the brass fittings maybe cost $15, and the Honda temp switches I got for free because I know the guy. The Volvo relay block did take a crap on me and a new one was $55, my cost.

A.J.

 

Nice write up! I'll post this as well as the others in the FAQ2 for others to use for reference.

 

One comment on how you mounted the switch, it isn't directly in the coolant, and sensors need to be as close as possible to the medium being measured or you don't operate at the setpoints desired.
I wonder if there is room for a 1" spacer block between the intake manifold and the radiator hose/thermostat housing....it would mean an extra thermostat gasket, but you would have a nice place to mount the sensor, just drill and tap a hole in the side of the spacer.

 

The heater core has constant coolant flow. Water conducts heat better than air. The coolant directly touching the sensor may not be flowing but the coolant flowing past the stagnant coolant touching the sensor is going to change temperature as fast as the coolant going past. That's why water to air intercoolers are so much more efficient than air to air intercoolers. Also with the Honda temp sensor opening at such a low temperature (200*) even if there is a 10* lag, I'm okay with that. With the 180* thermostat I have in there, my idiot temperature gauge stays at about 1/4. When sitting at a red light, the hottest it gets is to the left of middle. With the 195* thermostat and the mechanical fan, it was always in the middle. Some may argue that it's now too cold. But with the fact that Chrysler heads crack so easily, I think colder is better, as long as I'm reaching closed loop in the computer. With my Snap-on Solus Pro hooked up reading the computer, the temp the fan comes on is about 200* (maybe a few degrees higher) and fan shuts of around 190*. This was the first modification I made to the truck. I should have posted it before my exhaust write-up. I did this back in the heat of an Arizona August because my fan clutch was crapping out (causing my A/C to not blow as cold at idle) and instead of spending the money on a fan clutch just to replace it with my electric fan, I had to expedite my electric fan. At first, I didn't even have the temp switch hooked up, it only came on with the a/c compressor. Since it was hot out and I wasn't going to go anywhere without the A/C on I wasn't concerned. So I've had this set-up since August and I am more than pleased with it's performance. Except for the junkyard relay crapping out and having to buy one for $55.

I like your idea about the 1" spacer block, but there is NO room back there. You've got the alternator to the right and the A/C compressor to the left of the thermostat. Also how much would a custom spacer cost compared to my $15 worth of brass fittings? For what, 2*-5* more accuracy? Anybody is welcome to expand or modify my ideas here to fit their needs. For cost and speed, I think my way is the best.

A.J.