Charging Problem

[MileHi50]

Hello everyone,

I just heard about the forum today so I signed up. I've been having some difficulty with my car lately. I have a '89 Mustang GT. I am the original owner of it, and it just turned over 58,000 miles. I'm hopeing that someone here may of already had the troubles I'm currently going through and can offer some advice.

My voltmeter started to fluctuate back in May, after I started driving the car again from it's hibernation over the winter. I replaced the alternator with a brand new one from Napa thinking that the original one was tired after 14 years. Well the gauge worked ok for a few days and then it started to fluctuate again. It was dropping down to the 10-11 volt marks on the gauge. It has always sat between the 13-14 marks for all it's life until now. Well they replaced the alternator, and things were ok again for a few days and then the gauge started to drop again. I took the alternator out of the vehicle and had it tested in several shops, trying to rule out any incompetence or mistakes. And it was good everywhere that checked it for me.

My question is, what do I do now? Is there a wiring problem or just a bum voltmeter in the dash? I'd appreciate any and all advice.

Thanks
Jim

[HiFlow5 0]

Hummm, interesting. Are you having troubles starting the car at all? How old is your battery? Are you running underdrive pulleys? When I run underdrives my volt meter reads 11 volts at idle and 12-13 volts driving. With the stock pulleys the volt meter reads 12-13 volts at idle, and 13-14 volts driving. I also have an aftermarket gauge cause the stock one is worthless when it comes to accuracy.

[MileHi50]

Hi there.
No trouble starting the car (yet). Just tap the key and it fires right up.
I bought the car brand new on 6-29-89. It has 58K miles and is embarrassingly original. The tires on it are over 12 years old now (2nd set). Original clutch, brakes, etc.

Anyways, right now the gauge is just sitting at around the 11 volt mark. It's not fluctuating anymore, it's just down today. I parked it after driving it like that for 15 minutes, and it started right up. I pulled the alternator again and went to Napa this afternoon and had them check it. Looks good. Went to Autozone and had them test it. Looks good.

The battery is 1 year old. I had the guys @ Napa check it out and they did a load test and it works just fine.

I am thinking that possibly the gauge has gone bad. My speedometer has also gone beserk this week-end and I think it's broke. Still puts on the miles, just reads real crazy like 140+mph while doing about 50. Fuel gauge also has been reading full until the tank is almost empty. I think I need to pull the dash apart and address all these problems.

What do you think about adding some decent Autometer gauges? They should install easily I imagine and be much more accurate.

Thanks

[Unit 5302]

Take a multitester. Put the positive lead onto the positive terminal and the negative lead on the negative terminal while the car is running and measure the voltage output.

Should read around 14 volts. If it's lower than 13.5 volts, something is wrong.

The Fox Mustang's have 2 12 gauge wires coming from the alternator that merge into a single 10 or 12 gauge wire about 12" away from the alternator. I've seen that connection go really bad before. Perhaps it's part of the problem? I've also seen my fair share of bad rebuilt alternators, hehe.

[MileHi50]

Alternator output is good. It is a "New" unit and not a rebuilt. It is quite possible the gauge is defective.

I am thinking of just replacing the stock voltmeter with a quality one from Autometer. I'm sure some of you may have added this to your 'Stangs already. Is it a easy install? Any particular model of voltmeter that you guys might like more than another?

[GTStang]

Autometer is the name in guages

[HiFlow5 0]

If you are having no problems starting the car and everything checks out ok, then I bet the gauge is at fault. I know my stock gauges differ from what my autometer gauges read. The autometer volt gaues is very easy to install. You will just have to decide what series you want to get now. I have the Lunar series, and love them.

[MileHi50]

Well today I was still driving with a voltmeter reading around 11-12 volts. Made several stops and then went home. Went back out after 10 minutes and the car would'nt start. The battery was dead. I pulled the alternator out and took it to Napa. They checked it and it failed. So I ended up with a replacement unit and also left my battery there to charge up.

After putting everything back in order, I checked the battery flow per the Chilton's manual. They tell you to close all doors and then put a test light between the + battery past and the +cable and see if it lights up. No light. So there should'nt be any shorts that are draining the battery.

Well I started the car and the voltmeter went up to the 13-14 volt zone where it has been all it's 14 years. So this is beginning to be weird. I hope to be checking the wiring this saturday to see if there is any problems. But I am beginning to think I have tapped into a batch of bad alternators, and my car is ok.

What do you guys think??