Why am I blowing fuses on my HI 2151/30WC or HI 2110WI?

I have a blank display and found the fuse was blown. When I install a correct replacement fuse, it also blows at power up. Why am I blowing fuses on my HI 2151/30WC, HI2110WI, or HI 2151/20WC?

The HI 2110WI, HI 2151/30WC and the older HI 2151/20WC weight controllers are equipped with MOV surge protectors. Surges, sags, and power incidents outside the voltage ranges for these units will cause the MOVs to short, which in turn opens the fuse. Replacing the fuse without checking the MOV condition will in all probability blow the fuse again. You will need to test the fuse and surge protectors.

The latest HI2151/30 has added two fuses on the output of the transformer.  This to fully comply with UL regulations.

WITH THE INPUT AC POWER PHYSICALLY DISCONNECTED:

Use an Ohmmeter to measure across the J6 AC power input (neutral and hot leads pins 1 and 2). An operational unit will read approximately 40 ohms +/- 3 ohms. An open reading indicates a bad fuse. A shorted RV1 or RV2 will show 5 ohms or less. Remove and replace the fuse, RV1 or RV2 MOVs, as required.

RV1 and RV2, 130 VAC MOVs Hardy part number 4802-0008
Fuse F1, ½ amp SLO-BLO Hardy part number 5103-0058

For more detailed instructions, please review the attached tech note.

NOTE: Units showing reading higher than 45 ohms after replacing the fuse, RV1 and RV2, should be returned to the factory for repairs. Units showing a shorted condition after replacing the fuse, RV1 and RV2, should be returned to the factory for repairs.