ELECTRICAL PUT NEW ALTERNATOR AND BATTERY ON. STILL WON'T START, DASH LIGHTS, AND HEATER WON'T WORK.

The regulator is inside the alternator. Get a new alternator or disassemble the alternator and install a new one. My option is get another alternator.

test the alternator it may be bad. but it could be something simple as a wire did not get hooked back up correctly. and then there is the other option you didn't disconnect the battery before working on the electrical system and shorted something out. check your ground wires and the plugs for the alternator and anything else you worked on. my neighbor worked on his Honda and it had three bad alternators and he had to go with the orginal expensive alternator to make it run again.

It is electrical, could be initiated by mechanical (shift lever mechanics are pinching a wire in reverse) or a shorted wire or solenoid in the reverse light system or transmission solenoid circuit. Need a detailed wiring diagram to determine path of circuit for that fuse. That is where you need to start. Try your local library or dealer for a service manual. Look Online also.

The new alternator is probably ok.
I would say you burned a fuseable link in the wiring harness.
The alternator has a fuse wire between it and the battery to protect it from overload.
Have someone check the wires coming out of the back of the alternator. The big wire should have battery voltage, the small wires energize the alternator when you start the engine.

Check your fusible link.It is tied into positive battery cable,goes to starter and alternator,it is burnt up.

Who told you the alternator was fine? Sounds exactly like an alternator issue, fuel relay cant stop your dash gauges from working. An alternator should be putting out 13-14.5 wolts with the car running. Do you have any lights on the dash? like a battery light or anything out of the ordinary?

CHECK ALTERNATOR FUSE AND FUSE LINK ALTERNATOR NOT GETTING NO POWER FROM BATTERY.ALSO CHECK ALTERNATOR WIRES CONNECTORS FOR DAMAGE OR BROKE WIRES IN THE ALTERNATOR ELECTRICAL CONNECTORS. I HAD SAME PROBLEM WITH CHEVROLET THE VOLTAGE REGULATOR WIRES CAME OUT THE CONNECTOR I HAD TO BUY NEW CONNECTOR CRIMP IT SOLDER THEN SEAL IT WITH ELECTRICAL TAPE IF FUSE AND FUSE LINK OKAY MORE LIKELY YOU HAVE DAMAGED WIRES AT CONNECTOR MAKE SURE DRIVE BELT TIGHT AND NOT SLIPPING.

CHECK ALTERNATOR DRIVE BELT COULD BE LOOSE NEED ADJUSTING OR GLAZED NEED REPLACING. IF ALL IS GOOD, CHECK ALTERNATOR VOLTAGE OUT PUT AT BATTERY SHOULD BE 13.5 - 14.5 VOLTS. IF NOT ALTERNATOR FAULTY BUT CHECK ALTERNATOR BATTERY FEED AND VOLTAGE REGULATOR WIRES FOR LOOSE CONNECTION OR DAMAGED FRAYED WIRES. CHECK ALTERNATOR FUSE.CHECK THOSE THINGS BEFORE BUYING NEW ALTERNATOR.FIRST TURN OFF RADIO BEFORE DISCONNECTING BATTERY CABLE TO KEEP FROM LOCKING OUT RADIO.

If both the alternator and the battery are good, either the alternator isn't turning fast enough (slipping belt or engine idle speed too slow), or you have a wiring problem.

To check your wiring, look for the "1" terminal on the back of the alternator (left side of spade terminal connector). When you turn the ignition key to the run position without starting the engine, the alternator warning light should be at full brightness. If the bulb is burned out, the alternator will not get the excitation current it needs to start up (it goes through the bulb). With the engine running, you should measure 12 Volts at the 1 terminal (this is the excitation terminal).

Another thing to check is whether the battery charge wire is good. If it is corroded inside at the battery clamp end or burned out, you won't get charging even though the alternator appears to be working. If you don't have an ohmmeter, you can make a quick test by adding a new 8 AWG wire between the output terminal and the battery clamp. If the battery now charges, the original wire is bad. If this works, I recommend installing an inline fuse at the alternator end no larger than the largest size used in your electrical system, just in case something happens to the jumper wire. That way you won't burn out your alternator.

The heater/AC issue could very likely be a separate problem, but inadequate power may keep that system from running properly. (Note: low idle speed or belt problems will also be detrimental to AC performance.)

It sounds like your alternator is bad. East way to confirm, take it to local auto parts store (IE: Autozone, Advance, etc) and have them do a FREE charging system test. Couple of thoughts; you have two new batteries and your poor alternator has to work twice as hard. After you put new batteries in, you've been running on straight battery power. Alternator normally runs all your electronics and recharges battery(s) but if Alt has gone "south" then you're on straight battery power.