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Discussion Starter · #1 ·
I have a 70 chevelle SS and when I step on the brakes or turn on the headlights the dash light dim for a brief moment. It’s the same when the headlights are on and I hit the brake the head light will dim for just a second. I know you are thinking regulator. The starter, alternator w/ internal regulator (110 amp) and battery are all new. What else could be the problem?
I’m guessing the there is a constant wire that comes FROM the starter and goes somewhere?? to keep the current flow consistent. I have considered adding a stiffening cap to the system but really don’t wont to vary that far from the factory set up. I have also considered putting it back to the factory way (it was altered before I got it) with the external regulator so the amp gage on the dash will work again…….. If anyone knows where the 4 wires for the regulator go (brown, white, blue and red) IE what wire goes to what terminal I would also appreciate that info or links / emails with wiring diagrams
Thanks for any help you can offer, Darren
http://members.cox.net/darrens70ss/
 

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Sorta think bad ground. Both the brakes and headlights rely on the ground wire from battery negative to the right inside fender. How's that looking?
 

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Discussion Starter · #3 ·
Thanks John,
I replaced both the positive and negative cables when I did the starter. The heavy gauge black wire goes directly the engine block (and the connections are secure and clean). There is also another heavy gauge wire from the engine block to the cars frame. Remembering my first chevelle without this problem there was a strap from the back of the block to the firewall. So if a bad ground situation could be caused by the motor and body mounts we may be on the right track. I will install another ground tonight (from the negative to the BODY) and post the results.

Big D
 

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Discussion Starter · #4 ·
Well I’m sure it didn’t hurt anything, except my wallet, another $25.00. But it didn’t help anything either. I found the ground connection you write of and it is clean and tight. Also added new ground straps from the inter fender to the frame and the block to the firewall. Symptoms remain the same. Any other ideas????????
 

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I would take an educated guess at the regulator or the alternator. If the dim condition is ONLY lasting a brief moment, it has to be one of the two.

Grounds or wiring problems would have a more lasting dim condition.

I have seen alternators do this prolifically and regulators as well. Something that is supposed to react to changing demand on the system is not working.
 

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Discussion Starter · #6 ·
That was my initial thought also. That’s why I replaced them with band new. Symptoms remain the same........
 

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make sure ground to inst panel is good
it is usually conected to the ebrake bracket and runs up to the dash cluster
also but not likely regulater may be adjusted wrong
 

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blue goes to alt (same color at alt)
white also to alt
orange goes to red on alt (this is always hot)
brown goes to bulkhead then inside to a y one is brown and goes to alt idiot light or gauge the other is brown with white stripe and it goes to ignition switch (this wire is a special resistance wire and if bad will need to be repaired properly to work)
 

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oh and the red wire is maybe the hot wire that may have been added when new style alt was added
also make sure to check main 12 volt junction mounted to rad support
 

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Discussion Starter · #10 ·
I have had the dash out and all the wiring is either new or in great shape. All 3 grounds associated with the gauge cluster are also clean and tight. http://members.cox.net/darrens70ss/Dash.htm

Does anyone know what wires are supposed to go to and from the starter?
1. Red battery terminal to the main post of the starter
2. Black wire with a purple trace to the same main battery post on the starter.
3. Purple (crank wire) to the small starter post.
4. At the battery I have a smaller gauge wire going to the horn relay. Is this the wire that powers the whole system? I’m thinking it has to be; it’s the only other B+ wire there is. I vaguely remember another heaver gauge wire coming from the starter and I think that’s the wire I’m missing. Can anyone confirm this??
:confused:
 

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1 main power from 12v to large stud
2 not sure about that one
3 purple to s stud
4 from 12v to junction block on rad support then to a three way split to horn buzzer, alt (red) and regulator (orange)
then from the buzzer to the bulkhead and to the unswitched power in the car
also there is the yellow (or maybe white) wire that goes to the i stud on the starter (this wire is needed for points ignition to keep enough voltage going to the coil during start-up
 

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Discussion Starter · #12 ·
Thanks Tom,
You are correct it’s a yellow wire. Not used on mine Hei. I think my problem has to do with the wire that goes to the firewall. I’ll replace that next.
 

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right on the fuse box the terminal that says batt is the power coming from the engine compartment
hook your meter up to that and your ground and then read the voltages when lights are on and you hit the brakes
there is a possibility you turn signal switch may be going bad which can sometimes cause problems that you would never expect
 

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Darren, that's a nice looking ride you have there. I'm impressed!


Are you running a one-wire alternator? If so, read my last post in this thread. You may want to make some changes.

If not, disregard. I can't add anything that hasn't already been said.
 

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Do you still have the origional style external regulator and alternator? If so, I would expect that you're seeing them work about normally. Even more true with a mechanical regulator.

I even see this type of thing occur on my 2001 S-10 a bit so it's not only limited to these old cars.

Peter
 

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Discussion Starter · #16 ·
No the car was altered before I got it and I have been trying to get it right from the first day I bought it. The starter, alternator (110 amp- internally regulated ) and battery are all new. With the external regulator removed the amp gauge in the dash doesn’t work and I’m still not certain that any of it is hooked up right. Going to give it a couple of days to cool off because now it’s just getting on my fricken nerves and this is supposed to be fun….!?
:confused:
 

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OK you have a good ground to the body and also the dash frame.
Using a larger gage clip lead:
Try jumping from the BAT terminal on the fuseblock to the input side of the tail light fuse. If you want to be extra safe use an in-line fuse holder with around a 10 amp fuse in it.
Pull the headlight switch out 1 notch and hit the brakes. Do the dash lights still dim?
Pull the headlight switch out all the way and hit the brakes. Do the dash lights still dim?
Just trying to see if it's on the positive side or the negative side causing the problem.
The ammeter is probably disconnected on one side but doesn't have much to do with these.
 

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Discussion Starter · #18 ·
Used a jumper wire going from the battery terminal at the fuse box to the positive side (towards the fender) of both the park fuse and the stop fuse nether produced any different results. Drove the Chevelle to auto zone and had the alternator and battery both checked just for piece of mind. Both tested fine. Relocated the ground for the taillights from the trunk latch assembly to a new clean ground site, this did not help either. * one thing to note the tail and stop lights still worked (but still not right) with that ground NOT HOOKED UP?
 

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So Darren,

Ya going to be a the HCC meeting on Sunday??? We could talk there about those pesky electrical gremlins.

Joe
 

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Discussion Starter · #20 ·
Possibly, can you give me a little more info like where and when?
 
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