Page 22 - Summer 2018 GMC Vintage RVing

Technical Corner MAINTENANCE, PARTS, TIPS, INNOVATIONS AND MORENew on the HorizonElectronic Viscous Fan ClutchTom Pryor | 1977 Superior | Lake Wales, FloridaThe GMC tribe has employed about a dozen of the repurposed Mercedes Benz “Sprinter Van” Electronic Viscous Fan Clutches (EVC). Feedback has been mostly positive with comments: “it cools as it should” and “I certainly know when the fan kicks in.”So much so the wife says, “What was that? Is everything okay? Are you sure?” Another wife says “it is the best Mod yet”.”The installation of the EVC is reportedly not problematic but the removal of the old horse collar shroud is the most time consuming. Once removed, the EVC adapter is installed with four bolts on the Oldsmobile engine water pump shaft. The adapter is a LH metric threaded flange that has been employed on virtually all-light truck EVC applications since early 2004. Screw on the fan clutch assembly, plug in the wire harness and attaching wires and coolant sensors are only minor challenges.Setting the “turn on” temperature has been the biggest negative. One owner used the Dynamic EFI EBL module to engageand disengage the EVC with temperature control features built into it. Nothing is perfect when repurposing new technology to our older coaches.Why is this fan/fan clutch not yet a home run?We have yet to unleash its full potential with a Mercedes Benz style control module. That module cannot be employed on our bigblock engines, as we have no engine control management system. The MB module isable to control the viscous flow within thefan clutch with a faucet strategy. When heat reduction is needed, the MB module signals the fan clutch to slowly open the faucet to start the fan and “ramp up” to reduce the engine heat load. Once the heat load has been reduced, the clutch slowly ramps down in such an elegant fashion that the occupants are oblivious to the cooling cycle. Sweet!The only cost effective control module types available to us are “DUMB ON/OFF” systems. “DUMB” modules are purposedto control electric fans. There are many available, but they all are off/on switches like our home heating/cooling thermostats.So what to do?Maybe nothing...but after months of research I have found a source that will supply a module for us to employ. The company is Automotive Diagnostics and Publishing (ADP).We would install the device shown on the bottom of the website page on a coach with an operating MB EVC. That device would have the ability to capture the required data for approximately ten test runs. With that data captured ADP would make sealed a module to cover the conditions we set-forth in test runs and too our liking. Go to the website for more information. If you have a continued interest in this project contact Tom Pryor at [email protected]/pulse_ width_pwm_controller_driver.htmlAfter some negotiations and soul searchingon our part, we now have brought thesehistoric molds back into the GMC Community. Below are some pics of these molds.In the upcoming months we seek to reinstitute selected molds as we find the technology to make them efficiently. For more information, contact me at 407-857-5777 or email me at [email protected] Molds are Back in the FoldJim Bounds | 1975 Transmode | 407-857-5777 | Cooperative Motorworks | gmccoop.comAs you know, the body of our GMC is made up of aluminum and SMC (sheet mold compound) which was heat moldedas all Corvettes have been since 1969.When General Motors cancelled our coach, they sold off everything...all remaining inventory right down to the molds which produced our SMC body parts.These molds changed hands several times over the past 20 years simply being stored.With the two sided front clip mold weighing in at 90,000 pounds, transportation and storage are major considerations, using them in some fashion for such small quantities simply has not been feasible.A big thank you to Don Wheat of Wheat Motor Company who has been the last owner storing these mammoth chrome plated steel molds here in Orlando some five miles from our shop.22 GMC VINTAGE RVING MAGAZINE | GMCMI.COM