Battery Failure and starter problems are about to drive me crazy

Our car managed to break down driving back from the beach this weekend (after we just fixed another problem). Here's what happened.
As soon as dark came (and we had to turn the lights on) we noticed that the battery power would start to die every time we pushed on the gas. It made it about 2 hours and then when we exited to get gas, the car died in the middle of the street. Not sure that it is the alternator because the battery would be stronger when we weren't pushing on the gas.
To give you some background, our car has been breaking down the past 2 weeks. I was having the same problem aas another guy who posted recently. The car would start intermittently - it would always turn over, but not start - usually when it was raining or humid. We replaced the ignition control system (we had a spare) and the car started working again. Then it died at the beach (before the dead battery) and a mechanic friend sparyed some starter fluid into the mass air flow sensor - and voila it started working. But then we broke down again on the way home.
So any advice would be great, we are pulling our hair out on this one. We have a spare volvo (another tragedy so spare parts aren't a problem). I know it is something stupid, but we're just having a hard time diagnosing.
Thanks in advance, Michelle
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Michelle
If the cars voltage is fluctuating like that, then the alternator, or its associated wiring is at fault. Things to check are drive belt tension (it could be slipping more at high revs or high load), security of the ground lead from the engine to the alternator, and security of the main positive output lead both at the alternator and wherever the other end goes, also, worth a check; is the charge warning lamp working? Many alternators need a small initial 'excitation' current to flow through the bulb, to the voltage regulator. Failing all this, the contact brushes on the voltage regulator (Bosch alternator) could be excessively worn, and struggling to maintain adequate pressure on the slip rings. The Bosch type regulators (complete with new brushes) cost about 12 UK pounds, the unit itself (a black inch diameter lump) is held on the back of the alternator by two small screws, very easy to replace, most likely to be the culprit, if everything else checks out.
TTFN, Ken
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Your battery is not getting charged while you're driving; the voltage drops when you get on the gas due to more load from the fuel injectors. They're having to open for longer periods...
Clearly, it's something in the charging system--start by cleaning all connections between the battery and alternator, including ground cables. Use a meter to look for voltage drops under load--with the headlights on, for example--starting from the battery negative terminal to the chassis, the engine, the alternator body, etc., until you see a noticable change.
Have the battery and alternator tested. Could be one of them.
Charge the battery, as well--you can drive quite a bit off of it when it has a full charge, especially during the day.
Gary
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