Flickering lights, engine power loss - Ford Mustang Forums : Corral.net Mustang Forum
 
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post #1 of 7 Old 06-09-2011, 05:02 PM Thread Starter
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Unhappy Flickering lights, engine power loss

My '84 SVO consistently has flickering headlights, interior, dash, and tail lights. Occasionally, the engine loses power dramatically, recovering after I give it more gas. The problem is most noticeable if driving around with the A/C on and the fan switched to high. Reducing the fan speed makes the issue less frequent. It's definitely some sort of electrical loading issue and I'm having a terrible time debugging it.

I've replaced the stock 1G alternator with a 3G that produces 145 amps... the voltage is good coming out of the alternator. Is this a bad ground sort of situation or what's up?


'89 5.0L LX hatch: all 90mm 2.2L Blowzilla Dart Iron Eagle 306 @ 8.4:1, ported Vic Jr heads, TMoss ported GT40 lower, Deka 80# injectors, EDIS8, GUFB-A9L2-Moates tuned, Tremec 3550, 3.31 gears w/31-spline TruTrac
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post #2 of 7 Old 06-09-2011, 10:49 PM
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I would definitely start with examining your grounds. Negative battery to engine block. Ground strap between the engine block and the firewall. Finally there is normally a smaller gauge wire coming from your negative battery cable to the inner fender.


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post #3 of 7 Old 06-10-2011, 10:58 PM
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My car has developed this same problem. My second Fox to have this issue. 89 and 1990. Both with the upgraded alternators but my 89 did it prior to that. The alternator went out on the 1989 and I installed a new one (this was about 4 years ago and I've sold the car). After installing the new one the problem was gone, then came back about a week later. I took it back and got a replacement. The replacement was only slightly better but eventually got worse. Then I put a 3G on it. The problem was noticeable but never got as bad as it had been. I sold that car.

My 1990 has a 3G. I have two heavy grounds coming from the engine to the chassis. Then from the engine to the battery and of course, battery to chassis.

I was thinking there must be some sort of issue with the charge wire in the dash not getting a good ground. Both cars have aftermarket gauges. So if you don't have the alternator wire connected, it never charges. It runs to the factory gauge. It's the only thing I can think of. I get 14-15.5 volts on my digital meter when charging.

With the A/C on and two condenser fans plus the radiator fan going, and A/C on high, I get great 14 volts consistently. A/C blows ice cold. Car runs well. No flicker.

I never notice the car running any different. Just the flicker and it's annoying. I may investigate the charge wire this weekend. I'll post up results if I find any.

FYI, I can also tell it's not related to the head light switch. The interior light flickers with the door open and no head lights on.

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post #4 of 7 Old 06-10-2011, 11:03 PM
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FYI, this is what I'm talking about... I think the current to this wire is causing the problem.


After I installed the Instrument cluster my alternator won't charge. What did I do or not do for this to happen?

When you disconnected the factory cluster the alternator circuit was opened causing the wire that energizes the alternator to be left open. In the instructions there was a special note about how to make sure the alternator would operate. What you will need to do is in the factory wire harness there are 2 wires that need to be jumped. You need to find a 12-volt ignition source and use the jumper wire that was in the electrical hardware bag and jump the 12-volt ign. wire to the Light Green/Red wire. What that will do is it will energize the alternator when the ignition is turned on. That will fix the problem of not having a charging alternator.

Information taken from here...

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post #5 of 7 Old 06-10-2011, 11:24 PM
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Wow, I just fixed it. As suspected it was the green / red wire coming from the alternator. There is a plug on the driver side frame rail area that I unplugged and snapped it back tight. I did that 3 or 4 times to rub off any build up on the connection.

I thought about it again walking out to the garage and remembered on my 1989 I built a new wire coming from over there. I think that is what solved 95% of that car's problem before I sold it and the remaining flicker may have been in the connection in the dash.

My 1990 tonight fired right up, no flicker at all. Zero.

So go find that plug and give it a try. Just trace the wire coming from the alternator. There should be a plug before it goes into the firewall somewhere. It will have several other wires going through it as well. I can take a picture of mine tomorrow if you need it but mine is a 1990, however it was 4 cylinder before the V8.

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post #6 of 7 Old 06-11-2011, 04:32 PM Thread Starter
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Quote:
Originally Posted by seijirou View Post
I would definitely start with examining your grounds. Negative battery to engine block. Ground strap between the engine block and the firewall. Finally there is normally a smaller gauge wire coming from your negative battery cable to the inner fender.
That was it! The small gauge wire from the negative battery terminal was totally destroyed. The car runs perfectly now with all the accessories turned on, including the A/C on max. The headlights still flicker, so I think there's something going on with the light switch, though... I'll take care of that later.

'89 5.0L LX hatch: all 90mm 2.2L Blowzilla Dart Iron Eagle 306 @ 8.4:1, ported Vic Jr heads, TMoss ported GT40 lower, Deka 80# injectors, EDIS8, GUFB-A9L2-Moates tuned, Tremec 3550, 3.31 gears w/31-spline TruTrac
'66 GT 2+2 Fastback: carb'd 289, Canfield heads - EFI transformation pending

'71 Mach 1: totaled - R.I.P.
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post #7 of 7 Old 06-17-2011, 07:33 PM Thread Starter
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Still working on the flickering headlights issue. The car runs fine otherwise. I've seen the AMP light turn on in the dash a few times when the lights decide to go really dim. Not common, but it occurs. Can you post a pic of the connector you mentioned previously? I'll see if I can find something.
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