Fan Disconnect
Q: My motorhome has a 1997 Chevy 7400 Vortec V-8 engine with a Banks lifetime air filter. Can you explain how to connect the air-conditioner fan to a switch so I can turn it on and off when I want to (only the fan, that is)? The reason I’d like to do this is when I go up hills in the summer months with the dash air on, the engine starts to heat up, the engine loses horsepower, and the fan clutch makes a lot of noise. By making this modification, I could turn off the dash air-conditioner compressor and leave the fan on until I reach the top of the hill, at which time I could turn the air conditioner back on again. If I forget to turn the fan off, I don’t think it’s going to hurt anything. Do you disagree? The only other thing I can think of is that when the engine is running the air conditioner, the fan is running also. Is that correct?
Hope you can clarify this for me. The maintenance seminar that I went to suggested that we try this to keep the fan clutch from coming on too soon. Can you tell me why they would tell us to try this?
The older engines had a temperature switch in the radiator, and all you had to do was connect it to one of the wires and ground it out and the fan would come on (the ignition has to be on, of course). My radiator does not have a temperature switch on it.
Walter Terry, F187061
Union City, California
A: I understand what you want to accomplish regarding some modifications to your motorhome engine air-conditioning system’s electric motor-driven condenser fan and the air conditioner’s compressor clutch.
Allow me to possibly clarify some of these key engine components. The fan clutch is typically a round, finned aluminum-body device (6 to 8 inches in diameter) and is mounted between the large multiblade (front) engine fan and the water pump hub/pulley. This fan clutch is sealed and contains a viscous fluid. It must not be altered, modified, repaired, or serviced.
The compressor clutch is mounted within the pulley on the front of the air-conditioner compressor assembly. The air-conditioner fan “” which I believe you’re referring to “” is in reality known as the air-conditioner condenser fan. (Some engines have one large condenser fan while other engines have two smaller fans.) This is mounted directly in front of the air-conditioner condenser, which is a radiator-like device mounted directly in front of the large engine radiator.
To temporarily turn off the A/C compressor clutch (with a switch) at the bottom of the hill would remove some load from the engine and help control engine heat. In addition, to turn on the condenser fan (with a switch) at the bottom of the hill would add cooling to the condenser/radiator at the start of the climb to the top of the hill and help control engine heat. Typically, the original-equipment integral sensor may not turn this fan on until the engine reaches 235 degrees Fahrenheit.
This was done successfully for many years on the older non-computer-controlled carburetor engines and on throttle-body, fuel-injected, computer-controlled 7.4-liter motorhome engines (a big help in hot weather and high mountains). I suspect that there may be some misunderstanding or misinterpretation of certain details, possibly by someone who may have presented this idea to you.
Your 1997 Chevy 7400 Vortec engine with electronic fuel injection is a fully computer-controlled OBD-II system, and the air conditioner may be controlled by a body control module (BCM). That is not to say that your suggestion can’t be done. I am saying that a lot of research and planning would be required to accomplish this without (possibly) turning on the “Check Engine Light,” which may create false trouble codes in the engine computer.
Goodyear Tire Information
Q: I need some advice about some Goodyear tires I purchased. When I got home and inspected them, I noticed that several had the DOT information “ground off,” and I couldn’t tell anything about their date of manufacture. I’m wondering whether they would be legal, for if not, I will take them back. Would you know the answer to this question?
Mike Warr, F309302
Cherry Valley, California
A: Tires have the DOT information on only one side. If you can’t find the information on the sidewall facing outward, check on the inside of the tires. I’m sure you’ll find it there.
Suspension Trouble
Q: I enjoyed your explanation regarding suspension trouble (“Suspension Question,” September 2005, page 20). One thing I think you missed is bell crank wear. The bushings used in the original equipment can wear out within 5,000 miles. I had a motorhome built on a 1990 P-30 chassis and had to change both bell cranks by 10,000 miles. Thanks for a good answer.
Willard Lasseigne, F50305
Lafayette, Louisiana
A: You’re right. I did not mention the bell cranks because I was unaware that they could wear that quickly; however, I have since learned they can. Bell crank replacement is covered in the suspension-related article that appears in the February 2006 issue of Family Motor Coaching.