lights flickering at idle

[pollock]

I noticed this morning that my headlights, instrument lights, HVAC panel backlights, and the lights in my autometer gauges are all flickering at idle.

Just above idle, it goes away.

Voltmeter is solidly at 14.5 V. Alternator is maybe 1.5 years old.

Any ideas? Should I just have the alternator checked?

[1987cp]

What charging system do you have? The only experience I have with that symptom was when I was driving a 1G car ('79 Squire) with a bad regulator. Charge voltage looked fine at the battery, but $10 for a new regulator fixed the flickering.

[pollock]

Stock '89 grand marquis.

[gadget73]

Dirty battery connections, dirty connections at the regulator, and/or bad grounds can cause this. A bad voltage regulator will do it too, and so can a cooked rectifier in the alternator. If the connections are all good, I'd have the alternator checked. Could also be flaky connections at the voltage regulator plug, and in the plug where the regulator connects to the body harness over on the passenger side fender.

[1987cp]

BTW, you'll probably want to take the alternator off and take it into the store. Some auto parts stores only check your charging voltage.

An '89 could have a 1G if it's equipped with that fancy windshield deal. Does your alternator have just two plugs on the side, or does it have one or more studs on the back?

[pollock]

BTW, you'll probably want to take the alternator off and take it into the store. Some auto parts stores only check your charging voltage.

An '89 could have a 1G if it's equipped with that fancy windshield deal. Does your alternator have just two plugs on the side, or does it have one or more studs on the back?

I am going to take it in for a test.

My alt has 2 plugs on the side.

Is there a link where I can read up on 1G vs. 3G? I don't know what that means.

[gadget73]

1G is externally regulated. If you have a silver box on the driver's fender that says Electronic Voltage Regulator, thats what you gots. Stock on everything till 1985, and stock on cars with the 100 amp alternator after 1986, usually those are InstaClear windshield cars but police cars have them too. Early are about 55-60 amps, but there is a 100 amp version.

2G is internally regulated. It has two plugs, one for the voltage regulator and a larger one for the charge output and stator input. This is stock on most 86+ and produces 65 amps.

3G is an evolved 2G, same voltage regulator but uses a stud for output instead of the plug. Internally they are revised for better low RPM output. Only panther these came stock on is the 1990 Towncar, but its a fairly easy job to stick one of these in place of a 2g and get better charge output. Common ratings are 95 or 130 amp.

[BigBrownVic]

ive been having this same issue since last week, everything checks out ok, but im gona try to replace that voltage regulator. my 91 LTD has the Instaclear windshield

[gadget73]

Check to make sure the bolts aren't rusty. The regulator grounds through those bolts, and if the connection isn't good you'll run into problems.

[pollock]

I took the alternator in for a test and it passed. It's less than 2 years old and the voltage regulator bolts look brand new still.

I checked the connectors, including the one on the inner fender and they all look good. I guess for now I'll just keep an eye on it - it's more of a mild annoyance than a real problem.

It's a 2G alternator, BTW.

[86GmLsCoupe]

I think the alternator is fine itself, but they really just have very poor low rpm performance. I had put in a "heavy duty" 2g about 5 years ago that had a stat sheet showing it peak around 118 amps, but I still had some flicker and it died after 2 1/2 years. I very highly recommend a 3g conversion when this alt goes, and it will.. You'll save yourself tons of headaches. Plus there's tons of info here on how to do the swap.