I have a recirculating pump connected to a 4 yr. old 80 gal water heater. This pump was replaced 10 months ago.
This week the hot water went out. Sandy deposits were in the water faucet strainers when using the hot water.

I replaced the two 4500 watt heating elements after draining the tank. I didn't check the anode.
After refilling the tank I'm not getting full hot water. It shifts between hot & cold (seems like the recirculating pump).
I increased the thermostat settings to about 135 degrees.

Any Ideas?

How do you check a thermostat with a multi meter?
How do you check the Pump?