1G weird elelctrical issues at idle

[excel8951]

I just bought my 91 talon tsi AWD and its running great; however:

At idle it seems to get starved for voltage. The head lights dim slightly and the battery, ebrake, and coolant light all "glow" but only at about half or quarter intensity. as soon as you give her a little gas every thing returns to normal but once the RPMs settle down, everything dims out again. the car seems to do this only at idle and other wise runs and acts absolutely perfect.

The alternator and battery are both new so I doubt its either. I know that the car is burning a bit rich and thought that maybe it might just be flooding slightly at idle and maybe I should lean it out a little using the MAF translator.

Any thoughts on where to start?

 

[Jungy]

What are your voltage readings at idle? Its a common thing with dsm alternators to run real low voltage at idle.

 

[Absit]

What's your tach drop to when you think you're "flooding"?
Check fuses and relays, have the alternator tested.

 

[excel8951]

The car idles at about 900 rpm. Measured the voltage and its about 12.1 volts at idle.

I noticed this morning that when I hit a puddle, the battery, ebrake, and coolant lights all come on at full intensity for about a second then go back out.

Any ideas?

 

[steve]

Sounds like the alternator is failing. You should see at least 13.6v at idle if the alternator is working.

Check the wiring between the alternator, alternator fuse, and the battery along with the grounds. Make sure the belt isn't slipping though they usually screech if they are.
If they are all good then it may be time for a new alternator.

 

[excel8951]

Checked the idle voltage again after letting sit for a while and dry out. Its up to 13.2 now.

Also noticed the belt looks pretty slacked at idle. Thinking it might just be slipping.

How do I increase the belt tension?

 

[GRAVEDIGGER]

12.1 volts isn't gonna cut it. Do like Steve said and check all the wiring, but I bet you'll find that your alternator is junk. I like to see anywhere from 13.5-14.6 volts from a good alternator.

edit* 13.2 volts still isn't enough
You tighten the belt by adjusting the alternator to pull the belt tighter.

 

[excel8951]

so i went to advanced and had the battery and alternator tested; they're both well within the specs which is what I expected from parts that are only one year old. I checked the wiring as well and did see a small exposed spot on the VR where the positive lead was exposed but didnt see any evidence that it had been shorting. I taped it just to be safe and alleviate a future issue.

despite all that, the car still acts up. I went home and started poking around and looked at the belt with the engine idling through the front left wheel well where the belt actually goes around the crank. The belt has slack to say the least; so much so that I pressed on the belt with it idling and could visibly see slack reduction. So my thinking is that the belt is stretched and slipping especially when it gets wet. The car had a leaky power steering pump until recently when I replaced the seal and I'm thinking that the fluid finally worked its way into the nearly new belt and that the belt dressing I applied to it may have reacted and actually made things worse.

I spent 30 minutes trying to figure out how to slack the alternator so I could get the belt off and replace it but on account of the 30 mph winds and rain, i said to hell with it and made an appointment for the local garage to replace it monday.

hopefully this is an easy fix

 

[TalonEvo]

Any update on this? I am having the same problem. The battery, brake, and coolant lights all glow but not fully light up when I drive it, and they actually seem to go away when I am idling so I may have a little bit of a different problem. I just had the alt tested and its perfect, and the battery is new as of yesterday. Getting 12v at idle, which is too low. When I turn on the blower fans, the radio temporarily dies out and comes back on. Sometimes the windows dont work when I first turn it on, but start working once I'm driving. the connections are very tight, but I'm definitely going to try changing the terminal connections and sanding down the ground connections because they do look kind of corroded. Is there a voltage regulator that could be going bad, or is this not a common problem with these cars?

 

[excel8951]

The belt replacement didn't fix it but a new alternator did.

I don't understand why the last went so quick but that was it.

 

[steve]

Top three reasons:

Heat
Fluid Leaks
Low Quality Rebuilds

The alternator is pretty close to the exhaust pipe and turbo. It's not unusual for the factory heat shields to be gone.

It sits under the power steering pump and often get soaked with oil and PS fluid.

The Auto Parts Chains tend to buy parts from the lowest bidder who in turn have to source parts from the cheapest places they can find. Put together, it's a wonder any of them work. They have a lifetime warranty thinking that you'll get a good one by the luck of the draw or give up out of frustration from changing them.