About a month ago I experienced a complete failure of the electric coolant pump on my FWC after a very low estimated operation time of 10 hours. The pump was the much cheaper Mustang supercharger intercooler pump, like $59 (made in China, referred hereafter as the Chinese pump). I had no specifications when I bought and tested it but the running amperage and flow were comparable to the 3X to 4X more expensive Johnson CM-30 pump. It worked fine up until it failed. I was fortunate it failed at the slip, more so that I was watching the temp gauge at the time so things didn’t get totally out of hand.
The Failure and Autopsy
It turns out the failure was not electrical as I first suspected. My alternator is pretty aggressive, puts out 14.7 volts. That output level is not by choice or design, it’s how the alternator was manufactured (non-adjustable). I became aware of the voltage during the hot coil, electronic ignition and ballast resistor studies. I thought the high voltage might have beat the stuffing out of the pump. I brought it home and took it apart. The design of the motor is a permanent magnet on a shaft that is surrounded by a coil. There are no brushes and no contact between the magnet and coil. Between the mag and coil is a plastic sleeve that was chewed up enough to bind the magnet thereby locking the rotor. I can't see the purpose of the sleeve but accept it is there for a reason. Reassembling the failed pump without the sleeve allows it to work fine. I was discussing this with another list member and he found the specifications online. The allowable voltage for the Chinese pump is 6 - 24 VDC so that wasn't the problem. The allowable liquid temperature maxxed out at 158F. Now there's a problem, I was running at 180 – 185. I sure could have used those specs before I decided to use the Chinese pump, they would have influenced me away from an attractive price. Speaking of price, I invested $118 + tax in two Chinese pumps (one installed, one spare) which approaches the cost of the Johnson CM-30 at $145 + no tax and free shipping so I didn’t save a red cent going on the cheap.
What to do about it
A quick check of the specifications for the Johnson CM-30P7-1 pump showed it's suitable for temps to 212F so we're good. Well maybe not so good. The allowable voltage range is much, much narrower, 12.0 - 13.8 VDC. According to the Johnson tech I contacted, operating outside those voltages will shorten the life of the pump. I'm way outside the range and striving to get a rock solid FWC system means I should stay within the mfr's specs. I’ve learned my lesson courtesy of China.
I bought the Johnson pump ($145 and free shipping, $75 less than I'd seen elsewhere) and also found an inline voltage regulator with adequate specs to tame the voltage at the pump. I bench tested the regulator and it performed well. Took it to the boat, installed it and couldn't get the output voltage greater than 10.8 volts (input of 14.5V down from 14.7V due to harness voltage drop). After more testing on the boat I found I could get 12.2V output with no load attached but still only 10.8V with a load (pump load). This won't do.
I contacted the seller and described the problem; he suggested I give the regulator higher input voltage. No, can't do that because it will wreak havoc with everything else on the boat, the voltage is a little too high as it is. And that's the last I've heard from him so the inline regulator idea is a no-go. Besides, installing it ahead of the pump gives me added complexity and one more component to fail. Good thing it only cost $8.
I suspect the regulator is affected by the pulsing nature of an alternator. That it worked on the bench suggests the power source for the test was steady. It doesn’t really matter, it doesn’t work in the intended application. Done.
The Solution
The Johnson CM-30 pump is installed and works great. My 100 amp Delco internally regulated single wire alternator I've bragged about so much is off to Lewco Electric in Newport Beach to have its regulator replaced with one a little lower, like 14.0V – 13.8V, the measured harness voltage drop of 0.2V will reduce it to 13.8V maximum at the pump meeting Johnson’s specification. 13.8V was the charging voltage standard for decades with an excellent performance history. If I sacrifice a little charge for the benefit of FWC it's worth it to me. Remember on the Catalina 30 we have no choice other than electric FWC due to zero space at the flywheel.
Tentacles that reach well beyond FWC
With this new, lower operational voltage I recalculated my ballast resistor and the existing resistor is still good, no need to replace but the recalculation needed to be done. Also, at the lower charging voltage I'm now married to conventional lead-acid batteries that I prefer anyway. No gels or AGMs in my future.
The Failure and Autopsy
It turns out the failure was not electrical as I first suspected. My alternator is pretty aggressive, puts out 14.7 volts. That output level is not by choice or design, it’s how the alternator was manufactured (non-adjustable). I became aware of the voltage during the hot coil, electronic ignition and ballast resistor studies. I thought the high voltage might have beat the stuffing out of the pump. I brought it home and took it apart. The design of the motor is a permanent magnet on a shaft that is surrounded by a coil. There are no brushes and no contact between the magnet and coil. Between the mag and coil is a plastic sleeve that was chewed up enough to bind the magnet thereby locking the rotor. I can't see the purpose of the sleeve but accept it is there for a reason. Reassembling the failed pump without the sleeve allows it to work fine. I was discussing this with another list member and he found the specifications online. The allowable voltage for the Chinese pump is 6 - 24 VDC so that wasn't the problem. The allowable liquid temperature maxxed out at 158F. Now there's a problem, I was running at 180 – 185. I sure could have used those specs before I decided to use the Chinese pump, they would have influenced me away from an attractive price. Speaking of price, I invested $118 + tax in two Chinese pumps (one installed, one spare) which approaches the cost of the Johnson CM-30 at $145 + no tax and free shipping so I didn’t save a red cent going on the cheap.
What to do about it
A quick check of the specifications for the Johnson CM-30P7-1 pump showed it's suitable for temps to 212F so we're good. Well maybe not so good. The allowable voltage range is much, much narrower, 12.0 - 13.8 VDC. According to the Johnson tech I contacted, operating outside those voltages will shorten the life of the pump. I'm way outside the range and striving to get a rock solid FWC system means I should stay within the mfr's specs. I’ve learned my lesson courtesy of China.
I bought the Johnson pump ($145 and free shipping, $75 less than I'd seen elsewhere) and also found an inline voltage regulator with adequate specs to tame the voltage at the pump. I bench tested the regulator and it performed well. Took it to the boat, installed it and couldn't get the output voltage greater than 10.8 volts (input of 14.5V down from 14.7V due to harness voltage drop). After more testing on the boat I found I could get 12.2V output with no load attached but still only 10.8V with a load (pump load). This won't do.
I contacted the seller and described the problem; he suggested I give the regulator higher input voltage. No, can't do that because it will wreak havoc with everything else on the boat, the voltage is a little too high as it is. And that's the last I've heard from him so the inline regulator idea is a no-go. Besides, installing it ahead of the pump gives me added complexity and one more component to fail. Good thing it only cost $8.
I suspect the regulator is affected by the pulsing nature of an alternator. That it worked on the bench suggests the power source for the test was steady. It doesn’t really matter, it doesn’t work in the intended application. Done.
The Solution
The Johnson CM-30 pump is installed and works great. My 100 amp Delco internally regulated single wire alternator I've bragged about so much is off to Lewco Electric in Newport Beach to have its regulator replaced with one a little lower, like 14.0V – 13.8V, the measured harness voltage drop of 0.2V will reduce it to 13.8V maximum at the pump meeting Johnson’s specification. 13.8V was the charging voltage standard for decades with an excellent performance history. If I sacrifice a little charge for the benefit of FWC it's worth it to me. Remember on the Catalina 30 we have no choice other than electric FWC due to zero space at the flywheel.
Tentacles that reach well beyond FWC
With this new, lower operational voltage I recalculated my ballast resistor and the existing resistor is still good, no need to replace but the recalculation needed to be done. Also, at the lower charging voltage I'm now married to conventional lead-acid batteries that I prefer anyway. No gels or AGMs in my future.
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