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Hey guys. When i use an accessory with a heavier electrical load at idle, it creates a noticeable drop in voltage. For example, if i turn on the flashers with the engine running i notice a slight, drop in rpm in time with the flashes. (this is also seen at night in the dome light, which dims significantly when the flashers are on.) When the head lights are switched on, i notice a corresponding drop in rpm at idle as well. When running the heater on the high setting. all lights are dimmed. These problems seem to disappear when the engine speed increases. Just because i had it handy, i replaced the alternator with a known good 1 I had on the shelf. I got the same result with both units. It was kind of a silly test because It almost acts as if its only running on the alternator. (like running a car with no battery at all) Now the battery IS about 3 years old. And driving a tow truck for AAA taught me that modern batteries are a blessing if they make it much longer then that. This one is a Delco unit, and it cranks strong, and can sit for days without seeming to loose any umph. Is this a ground problem? Maybe a corroded hot wire even? I don't like the idea of unintended resistance in these old wires, and id like to correct anything thats wrong for safety's sake. Its my daily driver, and my nephews are in the car almost every day. Thanks for any and all suggestions! Hope everyone's having a great night!
Is the idle speed correct? Connections clean and tight?
Measure the voltage at the battery with the engine running, all the accessories off. It should be 1414.2ish. Next turn on some heavy load accessories and then measure voltage again. Ideally, the voltage should be about the same. Next, measure the voltage at the charging wire stud of the alternator. Still should be about the same. If not, you have some bad connections or you need an alternator with more capacity.
Thanks for the response. When i mention "heavy load" i am referring to the headlights or heater. The car has no after market electrical accessories, apart from a retro sound replacement radio which only powers the 2 dash speakers and uses a negligible amount of power. It has occurred to me that the car was shipped with the current accessories, and lighting packages, and should operate correctly if the wiring is sound. That being said, the alternator has been rebuild by Hart Auto Electric in Glendora NJ and was beefed up to 100 amps. That should be more than enough to power factory accessories, and lighting. The alternator tested at 14.5 when i re- installed it after it's rebuild about 2 months ago, but this problem has persisted since i've owned the car. Ill have to re test everything tomorrow and report back.
I do realize that there will be a voltage drop/dimming effect when the car is idling in gear. This just seemed excessive is all. I guess i'm worried for nothing
Most electrical issues in a vehicle can be traced to the GROUND side of the circuitry. From the description in this thread coupled w/ the description in the phone charging thread, I would suggest you have a GROUND circuitry issue. A rock solid GROUND is the most important factor in any electrical circuit and should not be overlooked. To begin, you need solid ground wires - that means wires in excellent condition; if a 10 gauge wire is called for the GROUND, that's what it requires. It requires every strand in the wire to be continuous e.g. no fraying of wires, no breaks in wires, no corrosion of wires and good insulation of wires which have insulation i.e. accessories in particular.
Locate the (generally speaking) three solid GROUND locations on the car. I'm not familiar w/ the locations of a 1977 Cutlass. The GROUND wire from battery to engine block is critical to the entire car electrical circuitry. Examine the block location (sometimes tied into a ALT bracket or elsewhere) of the GROUND wire from the battery to the block. That wire needs to be rock solid big and beefy in excellent condition. Replace it if it is not. Clean each point of contact ANYWHERE a ground wire contacts the block, frame &/or chassis. Most often you have a GROUND from battery to block, battery to chassis (somewhere by the fan shroud) and a GROUND wire from the back of the engine to the firewall. Various devices use the chassis as GROUND. As you maneuvering about locating GROUND wires, note any peculiarities of wires which make no sense - i.e. a PO may have done anything to this car which has negatively influenced the GROUND path. Remove those wires in particular which go nowhere. OK, I've made my point - perform a thorough review of the GROUND wires. Clean each attachment locations thoroughly with sandpaper, wire brush, etc. and replace any wires &/or cable ends.
Hey, thanks for the replies guys. I'll check all my grounds, and replace whats necessary. The battery cables are factory as far as I know. Its a side post battery. I added a secondary battery to chassis ground, and replaced the engine ground strap. I'll probably replace the ground from the battery to block as well.
Hey, thanks for the replies guys. I'll check all my grounds, and replace whats necessary. The battery cables are factory as far as I know. Its a side post battery. I added a secondary battery to chassis ground, and replaced the engine ground strap. I'll probably replace the ground from the battery to block as well.
Original battery cables on these old dinosaurs can be replete w/ numerous areas of corrosion/oxidation which often can't be visualized under the insulation. Anyways, I think you're trending in a positive direction by examining ALL of your ground wires, terminals & locations. It really is a solid upgrade to maintaining electrical continuity. And, you're good to adding secondary grounds if necessary as long as they're located appropriately.
Ok, so ill definitely change the battery to block ground. Would it be good insurance to add a second engine ground strap? Or is that unnecessarily redundant?
The thing about ground straps is this. The metal (itself) to which any ground strap is attached and importantly - passes through - to any other area must be sound. Think of a big A$$ long floating piece of metal like a cargo container ship 800 feet in length. It may contain eight bulkheads or many more 15-20 bulkheads. Imagine that beast was built in 1950 and is nearing its time for a complete overhaul (it's most likely already had many). Bulkheads deteriorate over time (along w/ many other large pieces of metal). The electrical continuity along a 800' ship must be maintained. If one bulkhead is deteriorating at a far faster rate than others, any electrical devices w/in that area of the ship will begin to fail as they've lost electron flow w/ the deterioration of the metal bulkhead, in addition to any other devices which are (were) dependent on the original GROUND strap wiring. They often replace GROUND straps by securing new secondary GROUNDs into solid metal bypassing deteriorating metal bulkheads; either, maintaining the original GROUND strap or adding new GROUND straps. The important point is continuity must be maintained however/wherever the placement of the secondary ground straps since electron flow does not occur through a rusted out bulkhead. You can liken the same scenario in a car, plane, or other piece of equipment - you need solid metal.
Original side mount positive cable? These were notorious for corrosion under the insulation near the battery connection. Change it or at least take a good look to see if it has swelling under the insulation. I would even cut the insulation near the battery connection open to see what is under there. Very good chance your problem is there.
That's great information provided by stellar. Here's some pretty pics of a failed (GROUND) starrer cable on my Indian motorcycle. It often starts/occurs on most devices w/ erratic behavior of electrical devices/accessories which eventually give way to device failure(s). In this case/scenario eventually the bike gave up the ghost & wouldn't start. Would not have found this oxidation/corrosion unless I removed the insulation/sheathing. Center of the cable is perfect - not so much on one end.
Insulation revmoved One (this) side is good One (this) side not so good Appears suspect I wonder Yeah, not good Tough moving electrons through that mess
I just stopped on the way home from work and bought, and changed the negative battery to block cable. Things have improved considerably. If that cable was bad. Then i can only assume that the positive cable is weak as well. Probably another quick trip to the store before they close. Thanks guys for all the advice and pics. As always, its a huge help.
While it appears you've made progress in one area changing the battery>block cable, don't stop short of the remaining cables - sand, wire brush clean &/or replace terminal ends - you want continuity throughout the vehicle. Good Luck!
Will do! Thanks so much for all your detailed info and examples. The stuff about the ship was very interesting. I guess i never thought about how a big ship was wired. very cool that its a lot like a car at least as far as the grounds are concerned.
Will do! Thanks so much for all your detailed info and examples. The stuff about the ship was very interesting. I guess i never thought about how a big ship was wired. very cool that its a lot like a car at least as far as the grounds are concerned.
The actual point being is this. It is the metal which contains the electrons and where the electron flow occurs. Electron flow occurs in the metal of the vehicle. Without solid metal (metal-to-metal) contact, you will impede electron flow. When you call upon the battery and/or charging system of the electrical circuitry to deliver amperage &/or voltage, electrons must "flow" out of the battery and back into the battery. You want this flow to be unimpeded with little to no resistance that's why the GROUND path is vitally important in any electric circuit. When devices begin to falter, it's almost always the GROUND path has far too much resistance/impedance to electron flow - this is where continuity is vital.
The thing about ground straps is this. The metal (itself) to which any ground strap is attached and importantly - passes through - to any other area must be sound. Think of a big A$$ long floating piece of metal like a cargo container ship 800 feet in length. It may contain eight bulkheads or many more 15-20 bulkheads. Imagine that beast was built in 1950 and is nearing its time for a complete overhaul (it's most likely already had many). Bulkheads deteriorate over time (along w/ many other large pieces of metal). The electrical continuity along a 800' ship must be maintained. If one bulkhead is deteriorating at a far faster rate than others, any electrical devices w/in that area of the ship will begin to fail as they've lost electron flow w/ the deterioration of the metal bulkhead, in addition to any other devices which are (were) dependent on the original GROUND strap wiring. They often replace GROUND straps by securing new secondary GROUNDs into solid metal bypassing deteriorating metal bulkheads; either, maintaining the original GROUND strap or adding new GROUND straps. The important point is continuity must be maintained however/wherever the placement of the secondary ground straps since electron flow does not occur through a rusted out bulkhead. You can liken the same scenario in a car, plane, or other piece of equipment - you need solid metal.
I appreciated your comparison to a ship it brought back memories. I was ship's crew on the USS Dwight D. Eisenhower during dry dock for nind months. Man, they did so much work on that ship, there were three times as many civilains on board at any given time than ship's crew.
Ok, so ill definitely change the battery to block ground. Would it be good insurance to add a second engine ground strap? Or is that unnecessarily redundant?
Adding a ground strap is redundant. My 71 98 has a ground strap on the back of the passenger's side head and the negative battery cable goes directly to the block. There's no need for additional grounding if your battery cables are in good condition.
Grounding must maintain continuity through all of the metal of any device (in this case a vehicle). If there exist breaks in the metal (loss of continuity anywhere), secondary ground straps are often employed in both DC & AC circuitry to provide additional bonding.
No second battery. Everything seems to be related to the very corroded battery to block cable. I replaced it and all is well now. Thanks to everyone for all the advice!
No second battery. Everything seems to be related to the very corroded battery to block cable. I replaced it and all is well now. Thanks to everyone for all the advice!
Grounding must maintain continuity through all of the metal of any device (in this case a vehicle). If there exist breaks in the metal (loss of continuity anywhere), secondary ground straps are often employed in both DC & AC circuitry to provide additional bonding.
^X2^, As the cars age so do the factory grounds through dirty connections, corrosion to the chassis and degradation of the ground conductor/cable itself.
I think we’ve beaten this up nicely but I’ll add ANY time two dissimilar metals contact each other the rate of corrosion can be accelerated x5. x10, x50> more depending on the two metals and environments. 👌
