Friday was a beautiful day for a bike ride. The temperature reached the mid-70s and there wasn’t a cloud in the sky. Donna took off on her road bike and headed east on Adobe Street. Shortly thereafter, I unloaded my mountain bike from the trailer and took a ride.
There are nine canals in the Phoenix area that supply irrigation water. In addition to the nine major canals, there are smaller canals called laterals that interconnect the major canals. Some of the laterals are underground. Most of the laterals south of the Salt River are large ditches.
Eastern Canal south of University Drive
I followed the Eastern Canal, which was built by the federal government in 1909, south. I made a loop through Mesa and stopped in at a couple of RV lots to kick tires. I also stopped at two trailer sales lots to see if I could find a pneumatic tire for the front jack on our cargo trailer. I have a six-inch wheel on there now, but it’s made from hard plastic and doesn’t roll well unless the trailer is parked on a hard surface. If I drop the trailer in gravel, it’s difficult to move it. I didn’t have any luck in my search though.
Donna spent the remainder of the afternoon working. I went to Lucky Lou’s at 3pm for an early happy hour. I met up with the usual gang there.
Patrick, Leendert, John, Mike and Jodi at Lucky Lou’s
Mike Hall told me about a 1978 Mercedes 450 SL he’s working on. It has a cooling system issue – the electric fan doesn’t work. I threw out a few ideas, then told him I would stop by and have a look on Saturday.
When I arrived at his place on Saturday and looked at the car, I was surprised to see the radiator has an engine-driven clutch fan in a shroud behind the radiator and an electric auxiliary fan in front of the radiator. When we spoke the day before, I assumed it only had the electric fan.
Mike had a Haynes manual for the Mercedes, but it didn’t have any information on the auxiliary fan nor did the wire diagram show the fan circuit. I searched online but couldn’t find anything useful. I spent the next two hours following wires back to the fuse panel and relay panel. It was a real head scratcher. We had already confirmed that the fan motor worked by jumping power directly from the battery.
There are two temperature sensors in the cooling system – a single pole sensor and a double pole sensor. After looking around and thinking a bit, it occurred to me that the single-pole sensor was a simple temperature switch. The double-pole sensor must be for the temperature gauge.
I disconnected the single-pole sensor and had Mike turn the ignition on. Sure enough, I had battery voltage going to the sensor. Here’s what I was thinking. The single-pole sensor is probably a simple bi-metallic switch. It has a metal strip in the center made of two dis-similar metals. As the coolant heats up in the sensor, the metals expand at different rates, causing the strip to bend. When the strip bends far enough, it touches the metal housing on the sensor, grounding the circuit and the voltage at the connector flows. This low-current voltage activates the relay which, in turn, supplies current to the fan motor.
To test this theory, I grounded the wire connected to the sensor with the ignition key on. Voila! The fan started running. We have a defective sensor. It isn’t grounding the circuit, so the fan relay doesn’t activate. The single-pole sensor is easily replaced and the part is available online.
With that done, Mike bought me lunch at Red, White and Brew. I spent the rest of the afternoon cleaning up the engine compartment on our coach and re-securing some insulation that came loose in the compartment. I also cleaned and waxed the right rear corner of the coach. The lawn sprinkler behind our site sprays the right rear corner and leaves hard water spots.
Today is NFL Conference Championship day. I think I’ll hang out and watch football. Donna’s heading out for another bike ride.