My cobra 1500 watt inverted doesn't come on wen I

have you repaired the component that burned these resistors out? if not then you cannot replace them as they will just cook again.

The serial number on the unit case should be enough.

Here is the way to hook them up in series, or in parallel.
There are 3 batteries in top (series) pic, but a 4th would be added in same wiring manner. Disregard the letters "ve" in diagrams, but the +/- polarity is vitally important in hookup.
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Note that four 12v batteries hooked up in series will be 48 volts at the end terminals. (If all four are hooked up in "parallel" then the total would still be 12 volts).

If you want to supply a 12v inverter, you need to hook 12v batteries in PARALLEL.

should probably connect it straight to your battery or you are trying to use something that requires too much power.

Make sure the battery connection is solid, if the 12 V collapses at the inverter -> no power. If that is OK, make sure to apply first a known good load, like a light bulb, if that still causes a problem the inverter is broken :-(

Is your 12 volt source able to supply 1500 watts of power? You can't draw more watts out than you put in. What is your 12volt source? A standard automotive alternator cannot make close to 1500 watts.

It would show overload if you're drawing more power than it can supply. 1500 Watts is a very high output for an inverter but that is the maximum it's capable of. As with any electrical supply you should not draw the maximum power it's capable of as this can cause it to burn out. Around 1200 would be the max you should draw continuously. You need to check the power requirements of whatever you're running on it. Also you need to check that it's capable of taking 13.8 volts. If 12 volts is the recommended input, putting in 13.8 will increase the voltage output which could damage appliances being run on it.

Could it be L.U.P. it's really L.V.P. but the V looks like a U. If it is it's low voltage protection. If the incoming voltage drops below 10.5 volts, it begins to flash. If the voltage drops below 10 volts it shouts down. If you supply it with 12 v it should restart. If you don't have manual you can view/download one from www.cobra.com.
The low voltage could caused by low battery. Poor connetions. Wire too small for load being supplied.Inverters over 1500 watts will require #1/0 or larger cable, in the shortest possible length. NOTE: Cable size recommendations may vary among inverter brands and models; check the Owner's Manual for the model you purchase before you buy the wire for it.

in a word no!,,,,it cannot and you may blow it up if you hook it up to the 115ac volt supply,,,in side it there is a switch mode power transistor,,that bumps up the 12 volts to 115 volts it only works the one way,,that is 12 volts dc in and 115 volts ac out,,,,

Yes you can. Then it would now operate on 12 volts.