Where to start to find electrical problem?

I have a 99 astro van AWD. My fan only started working on the high setting last summer. Then I noticed the air conditioning never turned off when i had the fan on. Also, last summer I noticed that my gas guage needle would start to quiver back and forth really fast. I have been having hard starting problems for awhile now and I suspect it may have something to do with an electrical problem. It won't start now so today I'm going to try to address the issue. Yesterday when I cranked it I noticed the speedometer was moving around?! So my question is can anyone suggest a good place for me to start? I was thinking of removing the panel and taking a look at the switches that control the fan and heat. Could it be a problem with a wire? ...perhaps a relay...ground?

Any suggestions would be very helpful. I have a digital multimeter.

p.s. My cat Gary is getting pissed because I can't get to the store for new litter.

If those are the only electrical problems you're experiencing, it's doubtful they are related to one common problem. First check the fuses, then battery negative cable connections and body ground wire, both ends.

Areas to check:
Heater blower: High blower relay, passenger side underhood, near evaporator housing, (5 wires going to it, 2 orange, blue, purple, black.). Blower resistor is near the relay, it has 4 wires.

A/C compressor: Should be "ON" in all modes except "HEAT" and "VENT".

Fuel gauge quiver: Check the ground near the fuel tank. The fuel pump and fuel level sender use the same ground, that might be your hard starting concern as well.

Speedometer: Possibly low battery voltage, or a ground problem, (just a guess)

Hope this helps, post your results.

If your heater motor is only running on high, I had the same problem and it would be your heater motor relay located behind your windshield washer fluid bottle in the fan box. It is just a matter of removing the screws and pulling the old relay out and plugging in the new one. I can tell you that it was not cheap!

The heater blower relay is most likely my problem for my fan. The speedometer moving around is because of low voltage. (it only does it after cranking awhile and my battery gets low) I checked the ground from the fuel pump and it seems fine...although a little rusty it seems to be screwed tightly to the frame. The oil pressure gauge still moves a lot when cranking. It will actually sort of almost run sometimes after cranking...the engine kind of diesels for about five seconds before quitting. Yesterday I got it started under the same hard starting conditions. I drove it around and it ran pretty well..It felt like it was missing occasionally but did not stall. I hope it's not the fuel pump again as I already replaced the pump twice in the last three years. Could it be condensation in the distributer? It did the same thing last year at this time when it was rainy and damp. I keep it outside because I have no garage.

Thanks.

... I checked the ground from the fuel pump and it seems fine...although a little rusty it seems to be screwed tightly to the frame.

I hope it's not the fuel pump again as I already replaced the pump twice in the last three years.

Could it be condensation in the distributer? It did the same thing last year at this time when it was rainy and damp.

Thanks.

A poor ground connection could be what's causing your pump to fail. Take the bolt out and clean the terminal and the frame with a file or sandpaper.

Condensation is a possibility, distributor cap and rotor and/or plug wires should take of it .

I took off the ground bolt today and sanded it to the bare metal but engine still fails to start. The cap,wires and rotor and spark plugs are only a few months old. The check guages light stays on. Battery voltage guage seems low. If I keep the pedal floored while cranking it almost starts...it kind of coughs and gasps but doesn't quite start. I wonder if it could be the fuel filter? I haven't changed it in about 5,000 miles.

Have you checked fuel pressure lately?

Fuel pump operation:
The fuel pump circuits are designed to energize the fuel pump continuously any time the key is in the START position. When the key is in the RUN position the fuel pump will operate provided the engine is running. If the engine stalls, or is not running for any reason, the ECM will shut off the fuel pump after approximately 2 to 3 seconds.

Fuel pressure test:
Install the fuel pressure gauge to the test port near the distributor. Turn the key to the RUN position but do not start the engine. While the fuel pump is running, fuel pressure must be 60-66psi. After approximately 2 to 3 seconds, the fuel pump will shut off. Fuel pressure must remain between 55-60psi for several minutes. A drop in pressure below 55psi indicates a leak. The most likely place is the fuel pressure regulator, or the lines under the upper intake manifold.

No I don't have a pressure tester or the money to buy one right now.

Is the battery symbol supposed to flicker on and off when cranking?

Here's a link for a fuel pressure tester, inexpensive but will do the job satisfactorily.
http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=92699

The voltage regulator has voltage to it when the key is in the RUN or START position. When the voltage regulator detects alternator output, the voltage regulator turns off the battery icon. It's possible for the light to flicker or even go off during cranking, (normal).

Thanks for the link. I decided to try a new fuel filter. I replaced it and it started right up! I'm suprised the old filter was so clogged. I can never afford to keep my tank very full so perhaps condensation inside the tank or dirty gas? Anyway I'm happy it was a cheap fix. Thanks for your help.

Glad you got her going. Don't allow the tank to drop below 1/4 full. It costs the same to fill the top half of the tank as it does to fill the bottom half. ;)