Adding a 2-Speed Engine Fan to a Diesel Pusher Motorhome

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1 Adding a 2-Speed Engine Fan to a Diesel Pusher Motorhome Bill Halberstadt November, 2004 Ownership of a motorhome usually presents many opportunities for improvement over the original design and construction. After several smaller projects on my 2 year old 2003 Safari Cheetah 36 foot, rear radiator, diesel motorhome, I decided to change from the original direct drive fan to a two-speed version for the 330 hp Caterpillar 3126e engine. This document will describe exactly how I installed the fan and how it performed. The purpose is to let others evaluate the possibility of performing such an upgrade, or having it performed. Here are some of the reasons I decided to do the conversion: I have had three (count em; 3) radiators replaced in the two years, apparently due to gravel and other debris from the roadway being flung into the radiators by the fan. I did install a makeshift set of rock guard screens in the air path underneath the coach in the time between radiator replacements number 2 and 3. I believe that a fan running at a much slower speed (most of the time) will reduce the possibility of further damage. I have never seen the engine or intake manifold temperatures rise above normal, even under prolonged full throttle hill climbs. This indicates to me that I have enough excess cooling capacity that a two speed fan could often run at the lower speed. It wouldn t hurt to have the extra horsepower and fuel consumption back that is wasted by the fan at full speed. I am a retired engineer and cannot help fiddl, er, improving things. I had heard of other two-speed fan installations, usually on Cummins engines, and scuttlebutt had it that Horton was a reputable manufacturer of such fans. I called them and found that they did not have a ready-made fan drive for my engine and coach combination, but put me in contact with one of their product managers. He and I discussed the situation and Horton agreed to fabricate the necessary spacer to allow one of their units to fit my application. Following are the steps I took to prepare for and to perform the installation. If your coach is not a 2003 Safari Cheetah, then, of course, many specifics will differ. Performance data and conclusions are at the end of the document.

2 Installation: 1) Remove the radiators. In my case there are three, as shown here: Turbo charge air cooler on top; engine radiator on bottom; transmission cooler at right (covering upper right quadrant of engine radiator). Removal was pretty much just identifying and removing obvious bolts and clamps, after removing a plastic air dam above the charge cooler. I did loosen the overflow tank and move it to the left. The transmission cooler will swing back and to the right, out of the way. The charge air cooler has two large clamped connections, one on each side. The engine radiator has two main clamped connections, both on the left, plus a small tube next to the upper main connection. Despite looking like a close fit, the main radiator does slide easily out the rear access doors. Be careful not to damage the delicate radiator fins.

3 2) Remove the fan. It is now very accessible, and held on by 6 bolts. After removal, you will be looking at this (note also the rock guard screens I installed previously): Radiators and fan removed (belt partly removed, but no need to do that)

4 3) Remove the hub-to-fan spacer. This is the six-pronged spacer in the photo above, and probably requires a few hits with a soft hammer. Here is a close-up of the spacer and the appearance after it is removed: Close-up of hub and spacer After spacer removal

5 Here are the parts I received for the fan upgrade: Electrical connector Spacer New fan (with 2-speed drive mounted), spacer and electrical connector 4) Mount the new spacer to the original hub. I used red Loctite on the six bolts: New spacer mounted. Threaded portion toward you is left hand thread.

6 5) Preparing the fan: Mount electrical connector to the matching prongs on rear of fan drive. I used Loctite on the two screws at the fan drive end of the connector (screws not in place yet here): New fan drive with electrical connector plugged in. 6) Mounting the fan: Temporarily hold fan up to hub spacer and thread it on a turn or two (counterclockwise). Move electrical connector around (it swivels 360 degrees around the fan axis) and check for best location to secure the end of the plastic wire support. I ended up using a long bolt threaded into an engine mounting hole. I then removed the fan and applied red Loctite to the spacer threads before putting the fan back on. The left hand threads should be secure, but I did maneuver a very large set of channel-locks behind the fan to snug the hex-headed nut that holds the fan drive to the spacer.

7 You can now secure the electrical connector plastic wire guide. Note that I used a stack o washers on the long bolt to provide the necessary spacing between the engine and the connector wire guide mounting tab. You may find a more elegant method: Electrical connector guide mounting. Make a secure waterproof splice of a wire (long enough to reach a good ground point) to the black wire from the fan drive, and another wire (long enough to reach the electrical bay) to the white wire from the fan drive.

8 The installation now looks like this: New fan completely mounted. Electrical wiring: Note the white wire above. The fan electrical connector has one white and one brown wire. The brown one goes to ground. The white one connects to the white wire seen above, which I routed up to the electrical bay (wherever most of the 12 V connections and relays are in your coach). Make sure all connections near the fan are very secure and waterproof. You can now replace the radiators, air dam, and reservoir bottle and reconnect all radiator and cooler connections. The ECM (engine computer) on the Caterpillar 3126e engine has an output signal meant to control 2-speed fans such as this. Based on engine coolant and intake manifold temperatures, the computer puts out 12 V for fan low or 0 V for fan high. This is the same logic the Horton fan drive uses, but a relay is needed to isolate the computer and handle the current requirement of the fan (2 amps).

9 Here is a diagram of the electrical circuit: I used 14 gauge wire throughout, but 16 gauge would be adequate. The relay could be similar to those already in the coach, or one commonly used in headlight circuits, as found in auto parts stores. It must have a set of normally open contacts, rated for 5 amps or more, continuous duty. The 5 amp fuse should ideally be located closer to the ECM connector than I placed it. The switch is twoposition. The optional indicator light could be integrated within the switch. The purpose of the switch is to permit the fan to be set to always high if desired. The signal for fan control comes from pin 11 of the ECM-to-chassis connector. This is not the other connector to the ECM, connecting to engine sensors, but the one connecting to coach chassis circuits. On my coach, this connector is almost inaccessible. To reach it, I had to remove the engine air filter and perform some contortions. Since pin 11 did not already have a wire at the connector, I obtained a socket (female) pin from my local Cat dealer, with about a foot of wire already crimped to it. To install it, you unscrew the connector screw, unplug the connector, then push the white rubber plug out of the pin 11 position. Then push the new socket pin into the connector until it locks into place with a click. Replace the connector and tighten the screw. Use a waterproof splice to connect this wire to the long wire that will be routed to the 12 volt electrical bay. To illustrate the connector s location, here are 3 photos, each one from a position closer to the connector:

10 Clamp for air filter (removed) Connector almost visible View of right rear bay. Strap used to hold wires out of the way Air filter clamp Portion of connector Closer view.

11 New wire at pin 11 position Connector holding screw Close-up of connector. After routing the above wire and the wire from the fan drive up to the 12 volt electrical bay, install and wire the relay and fuse. Route the appropriate wires up to the driver s console and connect to the switch and optional light. Double-check the wiring for correctness. To the left is what the switch installation looks like in my case. The new switch is at upper right. The While the Cat ECM has the capability for fan control, the default is off. Any Cat dealer, and most other diesel shops, can reprogram the ECM to turn on this feature. You want the parameter Fan Control Type to be changed from None to On-Off. Optionally, you can have the parameter Fan with Exhaust Brake On changed from No to Yes. This will set the fan to high speed whenever the throttle is fully released, so that the fan will add a bit more drag to the engine as the exhaust brake activates, to enhance the braking.

12 The fan will be set to high (0 V to fan drive) whenever any of the following are true: Engine is off, or is cranking, or for 2 seconds after first reaching idle speed. Engine coolant temperature is above 205 degrees F (back to low at 198 degrees F). Intake manifold pressure (boost) is above 10 psi and intake manifold temp is above 162 F. Intake manifold temperature is above 189 degrees F (back to low at 127 degrees F). Exhaust brake has been on for at least 2 seconds. Active diagnostic code for colant temperature sensor failure. Switch at driver s console is set to Hi Any failure that causes loss of voltage to fan drive.

13 Performance: After installation, I noticed two things immediately: There is a significant delay between application of 12 volts to the fan drive and the fan actually going to low speed; and when the fan does go to low speed, there is an amazing reduction in noise. At low, with the coach parked, there is less air flow from the radiator area at any engine speed, then there was at an idle before. At high, the fan sounds and appears to move air, as before. On the road, there is a significant noise reduction at the driver s position at speeds below about 60 (the wind noise dominates at higher speeds). In the bedroom at the rear of the coach, the noise reduction is dramatic at any road speed. My vehicle is a 2003 Safari Cheetah motorhome, type A, 35 8 long, currently weighing 24,780 lbs. In all tests, the coach was towing a Jeep Grand Cherokee weighing 4,400 lbs. The coach engine is a Caterpillar 3126e, rated at 330 HP. At an engine speed of about 2000 RPM, it takes about 20 seconds for the fan to go to low after 12 volts is established. At about 1700 RPM (60 mph for my coach in high gear), it takes about 45 seconds. Below about 1500 RPM the transition takes at least several minutes (if at all). The fan will go to low during normal acceleration to highway speed. During a trip from Delaware to Oregon in July and August of 2004, I was able to acquire good operation data, mostly via my laptop computer hookup to the engine and transmission data bus, via SilverLeaf s VMSpc connector and software. This allowed me to monitor and log many engine variables, including coolant temperature, transmission temperature, intake manifold temperature, road speed, engine rpm, engine load, boost pressure, and fuel MPG. Averaging many separate segments of constant speed on level roads, with the fan at high or low, I found a 1.0 (±.2) MPG increase in fuel economy (from 7.5 to 8.5 MPG). Several 0 to 60 MPH runs on level ground averaged 2.5 seconds faster (to 31 seconds) with the fan on low. Horton estimates an available horsepower increase of 25 HP with the fan at low. One unexpected effect was that the engine ECM almost never commanded the fan to high. The only times it did so were long uphill runs at full throttle, with outside temperature around 90 degrees. This means that, for my coach, I will get essentially the full benefit of the horsepower recovered by not having the fan running at full speed. When the ECM did ask for high fan speed, it was almost always for engine coolant above 205. I only saw it go to high on intake manifold temperature a few times. The ECM command does not consider transmission temperature. I did not see it ever approach an overheat condition. Conclusions: For my coach, the installation took about 16 man-hours plus the price of the fan drive, a switch, a relay, a fuse, and some wire. I could do it again in about 8 man-hours. A professional could probably do it in 4. In my case, the fan will run at low speed over 99% of the time. The benefits are reduced noise, increased fuel economy and power, reduced chance of radiator damage, and perhaps

14 less engine wear. I am pleased with the results. I hope that this document will help you judge the pros and cons of such an installation for yourself. For information about possible fan drives for your coach, you can contact Horton at (800) Feel free to contact me as shown below, for any information about my installation. Bill Halberstadt 505 Lark Drive Newark, DE (302) halberstadt@mindspring.com Rev 11/28/04