Marine Air Systems error “HHH”

As the manual says, two things can cause the HHH error code on these common marine A/C units installed in many manufacturer’s vessels.

1. Over pressure of freon (unlikely unless recently serviced (by someone who didn’t know better)).

2. Lack of seawater flow from the seawater pump. Check: Is the A/C seawater pump turned on?!? If yes: Check strainer etc. How is the discharge / flow?

(This was NOT our problem as the flow was great / normal.)

3. NOT in the manual!

A third cause is a failure of this sensor switch, pictured below. It will fail OPEN protecting the compressor and prevent it from coming on. From what I’ve been told, a failed switch will also produce the HHH error on the panel.

This morning, a “neighbor” / dock-mate disconnected one of our two 30Amp shore power cords. It was for pole #1 which powers the A/C Pump (which provides seawater to both A/C units on our MS 390. The pump went off, and the forward A/C unit went off. However, the aft / salon A/C unit kept running until it failed with the famous HHH error code.

The aft A/C unit is on pole #2, which still had power. However, it was not getting any seawater due to the pump being off.

Once negotiating a restoration of shore power to our pole #1 with the dock master and everyone else on our dock, our A/C pump was pumping again and the forward A/C unit was back on.

Unfortunately, HHH persevered on the aft salon A/C unit’s control panel. Waiting 30, 60, 90 minutes did not help. The flows were great out of BOTH forward and aft A/C seawater return lines.

SOLUTION (temporarily): bypass this switch with a test lead, as shown below. IF the switch has failed, this bypass will get your A/C working so the Admiral is happy for a day or three. DO NOT stay operating like this for weeks … as it is unsafe. GET A NEW SWITCH! For example, if the same problem happens again to pole #1 there is nothing to protect the condenser running with this switch bypassed!

Actually, today I decided to combine both poles by using the “Parallel” breaker. So pole #2 is now piggy backing off of pole #1. If the power is disconnected, both the salon A/C unit on #2 and the A/C sea water pump on #1 will go off together sparing any chance of damage from the condenser running without sea water.

Details to follow on model number and source for the part.