toddk911

A. My voltage guage has been reading under 12 volts lately, sometimes jsut above the 10V line. BUT I had the bat and alternator checked out and they are fine. Also, when I have the low readings, I check with volt meter and guage shows 10.5-11 and the meter reads 12.5....?????

B. Could the alternator check out ok, but the voltage regulator be bad?

C. Can this issue cause hesitation/stumble in high revs/boost situations?

RKD in OKC

Check cables from alternator to starter and from starter to battery.

These are common places to lose voltage. It can be the cables or just the connectors.

toddk911

Ahh, ok thanks.

And could this cause not enough spark in the higher rpm/boost loads?

VWaddict

You're measuring at the battery terminals and reading 12.5, right?

There may be some voltage drop across the wiring between the two places. It may be on the high side or the low side (high=+ve, low=ground) -Only way to be sure is to measure at the gauge terminals, confirm 10-point-something volt reading, then measure between (1)the -ve terminal of the battery and the -ve terminal of the gauge... and (2) the +ve terminal of the battery and the +ve terminal of the gauge. WHichever reads the higher has the most drop. Might be through the fusebox on the high side, or bad ground cable on the low side.

as to (c), anything's possible...

Keith

toddk911

So where does the voltage guage get it's reading from?

VWaddict

battery to starter cable has no influence on voltage reading at the battery with no engine running, nor should the alternator to starter. -both should be removeable, and the voltmeter should be able to read battery voltage with the engine off, but the key in the 'run' position (not start... obviously!)

Those will cause either "slow turnover" or "slow charging" or both, but not cause the dash gauge to misread battery voltage.

Keith

ehall

Have you actually checked the VR? I've gone through two in the last 4 years.

VWaddict

It reads across the battery terminals, but not all the time. Like most things on the car, it's fused (sensibly) and it comes after the ignition switch. -so when the key is out, it's disconnected. Otherwise, when the ignition switch is on, it reads the full-time +12V (nominal) which the dash uses to run a few things like the lamp test on power on... etc.

Voltage at the battery terminals rises when the battery is under charge, so you have to be careful to take note of and state the condition (engine running/engine stopped) when noting voltage measurements.

Now, all conductors have at least a little bit of resistance (ignoring superconduction, which only happens at close to absolute zero, so I think we can rule that out in Florida!) and resistance causes voltage drop proportional to current. (V=IxR...) If the gauge reads lower as more and more electrical load is placed on a resistive conductor which forms part of the path which supplies voltage to the gauge (the gauge itself consumes only a tiny bit of current) then the gauge will be seen to 'modulate'... like if your turn signals draw current along the same resistive path for example, you'd see the voltage gauge 'twitch' to & fro in time to your turn signals... (Note: Turn signals, not 4-way flashers... since 4-way flashers take their feed from before the ignition switch, and turn signals take their feed from AFTER the ignition switch)

Of course, it's not only WIRES that become more resistive over time (corrosion, etc.) but also the points where conductors (wires etc.) meet other conductors... -such as the ignition switch itself, grounding terminals etc.

That narrows it down by... let me see... oh, not much!!!

Keith

Musche

When I had low voltage readings I would notice erratic behavior of all the gauges and average performance. I did two things, 1) clean the grounds on the back of the engine where the heater valve is located and added a ground strap from here to the firewall, and 2) clean the battery cables at the battery especially the smaller cables that attach to the side of the positive terminal and replaced the bolts that secure them. These were very corroded underneath where you couldn't see and the bolts were weak from corrosion. What a difference in the car! It starts right away, gauges read true, no dimming of lights, etc. I swear it seems like it has more giddyup than before. Something to check, anyway.

rberry951

Also check voltage from the hot side of the batter to the engine block, ground straps are also a point of failure on these engines.

Regards,
Russell

ehall

yep what they said. You really need to get in there and make certqain that you don't have any corroded, frayed, or unprotected leads. I went through this crap for almost a year before finding a battery to starter lead that was damaged and occasional, under heavy boost, would actually get close enough to the bell housing to arc and cause a momentary complete electrical failure. This is a basic problem but you'll need to do a bit of detective work. BTW, I found the bad lead after replacing a bad VR.

toddk911

So where does the volt guage get it's reading?

It seems, and it just started doing this, that once the car has been started and been running, when I go back later to start again it is fine. Only seems when sitting for some time. BUT, the battery is fully charged and alternator is good.

I have actually watched the gauge start at 12 and then on my way home from work, gradually get down almost to the 10 volt line. But I get home, check the volts and reads 12.5 on volt meter and turn the car off; same. then start back up just fine.

As usual....WIERD!!!!

toddk911

I actually have a new one, but have not installed as I did not realize you have to pull the alternator to do so.

toddk911

Ok. Might have to drive to your house

TD in DC

I had a problem with occasional stumbling and hesitation, and it turns out that I had a bad alternator. Apparently, these cars are very sensitive to voltage irregularities/fluctuations. As soon as I got the alternator replaced, the stumbles went away.