Anybody Know Electrical Stuff?

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Anonymous

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I'm back to getting my Falcon going after a complete rebuild on the engine. I've been struggling with a rough idle and a couple things are buggin me.

1) I installed an aftermarket ammeter under the dash and while the engine is idling, the needle is bouncing all over the place. Once the RPMs start to pick up the needle is steady.

2) I attached a diagnostic tachometer under the hood to help me adjust the idle speed. Every so often the needle drops off then picks back up again. It is almost like the engine missed a beat.

Anyone have any ideas? Are these two problems related in some way?

Thanks,
Jeff

63 Falcon Convertible, 200CID, 5200, 252 Comp Cam, Duraspark
 
Jeff,

I'll take a stab.

1) Do you have any other extra load equipment on your car? (ie: after market radio, ignition, amp, etc). If so, your alternator may not be putting enough power out at idle and what is happening is the alternator is getting overloaded. I had this happen on my old truck.

The other thing that could be happening is your voltage regulator may be going bad.

2) I thing #2 may have a small effect on #1 in that if you are misfiring occasionally, the alterntor may not be getting the required power to turn it enough to produce the required output for your car. That may be effecting you as well.

Slade
 
8) if you still have the stock generator, then that could be part of the problem. generators dont start charging untill the rpm's go over about 1500 or so.
 
Thanks.

I don't have any aftermarket items on my car. The only thing different is the addition of a Duraspark ignition.

Yes, I have a stock generator. The voltage regulator is brand new. Actually everything was changed out from the old generator over to an alternator when I built the 200. As soon as I touch the gas, things get steady the ammeter.

I haven't had the opportunity to get the car out on the road. I'm still trying to get it running right. My real concern is the tach dropping off. This might be part of the rough idle problem I'm having. Can the Duraspark module be defective and causing the intermittent pause?
 
It's possible the inductive pickup for your underhood tach isn't getting a good signal. Try a different plug wire and see if it does the same thing. Your tach doesn't care which wire you use.

Just as rbohm indicated, the generator has to be spinning pretty good to generate a steady output. Ever notice how your headlights dim when you come to a stop and get brighter just as you step on the gas? Check your voltmeter once you get the engine up off idle around 1500 - 2500rpm. If it's still bouncing all over, then you might want to double check all your connections, and verify all your grounds are clean.

Did you remember to polarize the generator?
 
I made a mistake and told you I had a generator. Sorry, I swapped out to a new ALTERNATOR and voltage regulator. Does this change anything in regards to the problem?

I just came from the garage after running the engine. The intermittent drop off on the tach went away. Probably due to getting a better connection on the tach this time.

My ammeter is still bouncing around. I want to get it on the road and see what happens.
 
YOu might try temporarily swapping a real VOM meter instead of the ammeter. This way instead of a needle you can get actual numbers and with the long meter leads you can pull it out for easy viewing. Then I would check the number of amps as you turn on/off each item of the car..IE.radio, lights, open doors, turnsignal, brake lights...also you can check the number of amps at different RPM levels. This might help you.

As I got through my old 66 I have found that many of the wires have corrosion on them inside the strands. (Green powder from the copper) As this condition goes on unchecked the resistance of the wire increases and more amps are required to do the same job. This is the source from the some of the fires and shorts that often happen in older cars. (Not to mention bad and frayed wire insulation.)
 
A bouncing ammeter comes from a relay & points type voltage regulator. I just hooked up my ammeter the other night and it jumps around at low rpm also. I still have the generator but I think the type of regulator is where that comes from or from worn brushes.

I like the needle type current and volt meters so you can see the surges that can happen. A digital meter requires a sample time and will smooth the reading out. I want to add a voltmeter which is more useful but I like having both. I'm going to add a large ciruit breaker where I hook to the battery cable at the starter relay in case my wire shorts to ground anywhere from there to the regulator where I hook back in. A short would create a fire from the red hot wire.
 
No doubt that sometimes analog is just the thing for real world info...and digital has its place...I have three Fluke meters avail to me and the are quite nice...one has a port to PC to sample voltage/amps for chart recording...much to sophisticated for the 66..but sometimes it can tell you alot....go with what you know..A portable meter lets you sample current at many different places in the harness to determine what draws the most current..for me its my lights..and wiring..so I am doing two things..new wires and LED replacement bulbs.(except for rear brake and stop)
 
The first thing you need to do is swap the regulator if you used the original generator version. An alternator specific solid state regulator is only about $15.
 
Is it the one-wire alternator? Mine won't do anything until it get's excited.... :oops:
 
Everyone, thanks for the input

I have a voltage regulator specific to an alternator system. It's brand new. It is not a one wire alternator system. Since the car has been sitting for some time now and I've cranked it over quite a few times already, I think I need to get it on the road (I've got some issues with my 5200) and get the battery fully charged up before I worry too much about it.

Thanks,
Jeff
 
OKIE....Taken out of context it is kinda funny....Mine wont work without permission ..(married with children)... I would like to explore the 1-wire system...do you have info on part numbers and how to wire..
 
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