The problem is they only have until Wednesday before the launch attempt has to stand down so that an Atlas rocket can be prepared for launch on Friday.
Rules dictate that only one launch vehicle can be fuelled and in the final stages of preparation at any one time. The next launch window for Endeavour opens on 8 May.
NASA management meetings to work out a plan are taking place as I write this and should be finalised soon. Then there will be a news briefing at the press centre at 1030 am (which should be aired live on NASA TV at 3.30 pm BST).
At the moment it seems the weather forecast is ‘red’ for Monday as well, with strong crosswinds and rain showers. It gets better if there is to be an attempt on Tuesday.
The electrical problem is likely either an open circuit in a hydraulic system fuel line heater thermostat or trouble inside an avionics box in the Shuttle's aft engine compartment.
Initial thermostat tests were consistent with a problem in the avionics box but engineers have not ruled out a connector problem or some other wiring issue elsewhere in the system.
If the problem can be isolated to an open circuit in a suspect thermostat, it is possible to install a replacement in time to support a second launch attempt this week.