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I remember a old tale of certain bearing failures in transmissions being caused by missing or unconnected engine to body ground straps. Can't remember the details and not sure if it was for real, but it makes sense. A load looking for a ground path- no strap- finds a poor ground path thru bearings- maybe some arcing??
Good possibility the issue is either (1) lack of ground wire from engine-to-firewall &/or (2) poor blower grounding. Since the issue (headlights dim) only manifests itself when the blower is turned on, it's likely the blower assembly (circuit) is faulty.
(1) There's a chance installation of the non-existent engine-to-firewall braided ground strap 'may' resolve the issue. If for no other reason, installation of this braided ground strap is required for a healthy ground system;
(2) Evaluate the blower ground wire. Since the blower case is fiberglass, the blower gains its ground from a dedicated blower ground wire connected to the firewall as depicted in the following diagrams. It needs to be secure, clean metal-to-metal - check its connection, remove it clean the ends, etc.
...when I turn on the blower motor and my headlight switch is on, I get a voltage drop. It only happens when the lights are on, and it doesn't matter if it's just the parking lights or if the headlights are on.
Dave, you've had the ground side of this problem well covered by Steve, Norm, Joe, and many other experts on this site.
However, there is a possibility that a supply-side problem co-exists. And it's easy to check for...
After you fix all ground problems, operate the engine at high idle, turn on your headlights and use your volt meter to determine voltage between the headlamp and the battery negative. If it's more than a few tenths of a volt below the voltage between the horn relay and battery negative, you need to attend to the voltage supply side.
Good possibility the issue is either (1) lack of ground wire from engine-to-firewall &/or (2) poor blower grounding. Since the issue (headlights dim) only manifests itself when the blower is turned on, it's likely the blower assembly (circuit) is faulty.
(1) There's a chance installation of the non-existent engine-to-firewall braided ground strap 'may' resolve the issue. If for no other reason, installation of this braided ground strap is required for a healthy ground system;
(2) Evaluate the blower ground wire. Since the blower case is fiberglass, the blower gains its ground from a dedicated blower ground wire connected to the firewall as depicted in the following diagrams. It needs to be secure, clean metal-to-metal - check its connection, remove it clean the ends, etc.
Norm, I discovered this just now...is this the blower ground wire? As you can see, it goes into a connector which isn't attached to anything.
Since I cannot see the other end of that wire I can’t validate. However, with that said considering it is a braided ground wire of/near the location in question I’d suggest it most likely is the blower ground wire. You should be able to validate via the CSM. Likely in the AC/Heater section(s).
Since I cannot see the other end of that wire I can’t validate. However, with that said considering it is a braided ground wire of/near the location in question I’d suggest it most likely is the blower ground wire. You should be able to validate via the CSM. Likely in the AC/Heater section(s).
It goes into this connector that isn't connected to anything. The other side of the connector has a brown wire which runs down under the fender and somewhere into the firewall area.
(1) Obviously, there's an issue w/ the ground circuit - no engine-to-firewall braided ground strap. Regardless what we find w/ that wire you posted, the engine-to-firewall braided ground strap is REQUIRED.
(2) Identify the true color of that wire you posted so it is perfectly clear what color that wire is. Wash it and make it clear exactly what color it is.
(3) That wire needs a new ring/eyelet if it is to be used for anything moving forward.
(4) Have you found the blower diagram & the wiring schematic for the blower assembly in your CSM? If not, find it.
It appears you have a significant departure from OEM wiring; yet, I can't validate this thus far.
(1) The connector you state isn't connected to anything is obviously incorrect. Oldsmobile didn't incorporate plugs which didn't connect to anything; therefore, it does not follow OEM wiring. Whoever wired your blower (at a minimum)...possibly the A/C as well was not following OEM wiring (it appears, thus far);
(2) Be aware a PO may very well have re-wired the blower - it appears they aren't following an OEM wiring schematic. Therefore, expect to see departures from OEM wiring I suspect. This will require you to trace/follow each of the wires to validate what wire is connected where. Additionally, this blower assembly may not be original to the car. You've already found some significant departures - don't expect this to be a simple Plug-N-Play resolution.
I wish I could state for you unequivocally: (1) that wire is a black wire; and, (2) that wire is the ground wire. I cannot. This is looking like baby steps to provide a confident resolution. Having a plug which supposedly connects to nothing, a supposed black wire which connects to nothing and importantly isn't even wrapped or secured so as to eliminate the possibility of a short & a missing engine-to-firewall ground strap speaks to someone having already spent time playing in the sandbox adding to the confusion.
Note the purple wire in your image, note the purple wire in the wiring schematic. Are they one in the same? Likely, I cannot validate across the Internet from my armchair. Time for you to start tracing wires.
I "might" make a suggestion - for what it's worth. "If" that plug is connected to nothing, it is 100% "useless" in its current configuration. "If" the black wire, supposedly connected to the useless plug, might be in fact, the normal OEM blower ground wire:
(1) You have no ground wire to the blower; or,
(2) A PO "may" have connected a ground wire somewhere else.
As said, this appears to be far less than a simple Plug-N-Play resolution; yet, it provides some indication of the issue you're experiencing.
I have not been paying complete attention to this thread. The "brown" wire that goes under the fender is the purple wire to the blower motor. Since the motor is bolted to a non-conducting fiberglass housing, there is a separate ground wire that connects to a spade terminal bolted under one of the motor plate mounting screws. The unconnected black wire in the photos is not that motor ground wire.
I have not been paying complete attention to this thread. The "brown" wire that goes under the fender is the purple wire to the blower motor. Since the motor is bolted to a non-conducting fiberglass housing, there is a separate ground wire that connects to a spade terminal bolted under one of the motor plate mounting screws. The unconnected black wire in the photos is not that motor ground wire.
So then it would seem the motor ground wire is non existent...super. Any idea what that connector that isn't hooked up is for? Maybe it plugged into the compressor? Seems to make sense since a PO removed the compressor.
So then it would seem the motor ground wire is non existent...super. Any idea what that connector that isn't hooked up is for? Maybe it plugged into the compressor? Seems to make sense since a PO removed the compressor.
There's no way to know without looking up under the fender. A mirror and flashlight might help.
I dunno...my head hurts at this point...lol. Is there a blower motor ground wire? Is there not?....if so, where?...if not, where do I connect it? At this point I'm going to hook up the grounding strap and go from there. Too big of a pie to eat all at once...lol
Joe, that would indicate that I would have to crawl up under the dash to verify the connections noted above, correct?
No, that is on the engine side of the firewall, under the fender. As I said, try a mirror and flashlight, or better a borescope. Sometimes you can stick your cell phone in there and take a picture.
No, that is on the engine side of the firewall, under the fender. As I said, try a mirror and flashlight, or better a borescope. Sometimes you can stick your cell phone in there and take a picture.
Ahhh...ok. Whew...I thought I was going to have to get in all kinds of crazy positions...lol. I'll see if I can take a peek.
The flat, two-wire plug is definitely the compressor plug. It even still has the ground jumper. It should have a dark green wire inside the wrinkle tubing.
I have not been paying complete attention to this thread. The "brown" wire that goes under the fender is the purple wire to the blower motor. Since the motor is bolted to a non-conducting fiberglass housing, there is a separate ground wire that connects to a spade terminal bolted under one of the motor plate mounting screws. The unconnected black wire in the photos is not that motor ground wire.
Joe, if the purple wire is power to the blower motor, and in my case, the purple wire is on the other terminal of that plug that is disconnected, then how am I getting power to the blower motor?
So then it would seem the motor ground wire is non existent...super. Any idea what that connector that isn't hooked up is for? Maybe it plugged into the compressor? Seems to make sense since a PO removed the compressor.
Please confirm what you've stated (above).
Currently, is there an A/C compressor installed in your car or is there no A/C compressor installed in your car?
Joe, if the purple wire is power to the blower motor, and in my case, the purple wire is on the other terminal of that plug that is disconnected, then how am I getting power to the blower motor?
Take a break.
Then read posts 63 and 55 again.
The disconnected plug goes to the A/C compressor. The wire on the other terminal of the disconnected plug is green. The disconnected ground belongs in the A/C compressor coil circuit. That plug has nothing to do with the blower motor.
I was wrong...the other wire on the plug that is disconnected is in fact brown, but I got crossed up when tracing it and thought it was the wire that goes down under fender. It actually goes to this plug on the side of the housing.
Brown wire on disconnected plug...
Brown wire at the plug on the side of the housing...
...what is that plug for?
I have not been paying complete attention to this thread. The "brown" wire that goes under the fender is the purple wire to the blower motor. Since the motor is bolted to a non-conducting fiberglass housing, there is a separate ground wire that connects to a spade terminal bolted under one of the motor plate mounting screws. The unconnected black wire in the photos is not that motor ground wire.
Originally Posted by 72455
Joe, if the purple wire is power to the blower motor, and in my case, the purple wire is on the other terminal of that plug that is disconnected, then how am I getting power to the blower motor?
Agree w/ Gary it's getting late & likely time to give this a break. I'm either misinterpreting Joe's original statement (above) or I'm not clear on what wires are connected in this "connector" itself. The purple wire is the "HI" side of the blower relay, it is a direct feed from the blower motor terminating into the blower relay. The brown wire is independent of the purple wire. Since this connector is only used for the A/C compressor it can be eliminated from discussion.
Dave - The purple wire you provided an image of should run from the blower motor to the blower relay. The purple wire feeds (gets it power) from the battery [black/orange wire (No. 8)].
Yes, determine if you have a ground wire [This!] at the location indicated in the (below) diagram. Don't worry about other ground sources I've identified (yellow arrows), find out if you have a ground wire at the blower motor.
Another possibility...how do we know the alternator isn't giving up the ghost?
While I can appreciate the value and importance of checking all the grounds and etc......I would not go too far down the diagnostic path without first checking and verifying the alternator output either on the car or off with a volts/amps tester. I've rebuilt far too many alternators with this same problem in my years of playing with cars. Always check the simple things early to save you from tearing the car apart or your hair out at the beginning. A good volts/amps tester can load the alternator and provide info on the output. Once you have this verified, I would go further with the grounds and other potential wiring issues/concerns. Grounds are very important in making things work correctly.
While I can appreciate the value and importance of checking all the grounds and etc......I would not go too far down the diagnostic path without first checking and verifying the alternator output either on the car or off with a volts/amps tester. I've rebuilt far too many alternators with this same problem in my years of playing with cars. Always check the simple things early to save you from tearing the car apart or your hair out at the beginning. A good volts/amps tester can load the alternator and provide info on the output. Once you have this verified, I would go further with the grounds and other potential wiring issues/concerns. Grounds are very important in making things work correctly.
Ok..so here's the next question. If the alternator was the issue, would I not get a light on the dash?
Ok..so here's the next question. If the alternator was the issue, would I not get a light on the dash?
No. not necessarily. Those idiot lights are not all that informative and if the alternator is still charging but is not providing full amperage under load....it may not trip the light. I would just check it if it were me and move past that potential issue right off the bat.
Thank you, Steve. That's a very nice, thorough document. As young mechanics during the early alternator era, we had some of this memorized.
I'm not clear on point 3... Should there be zero VDC or battery voltage at terminal 3?
3. Reinstall alt 2-wire connector, leave 4 lead reg connector disconnected. Engine static, key on. Verify battery voltage present at terminal #3 (the black terminal retainer/connector on the reg is numbered F,2,3 4). There should be zero VDC on terms 2, 3, 4.
Gary
Thanks, Gary,
I corrected the typo and uploaded the edited PDF thanks for catching that. See corrected document on POST # 24
Steve
Ok, I hooked up the ground strap to the firewall and the engine block. It helped, but I still have a voltage drop. With the headlights on and the blower motor running at idle, it drops from 13ishV to around 12V. In gear, it drops to around 11V.
