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I noticed my new battery seemed to be getting tired, and while running tested the voltage at the POS & NEG and found it just under 12V. Made sure wiring was all intact at alternator and regulator (rather a quick glance and push on 4-wire connector at regulator) and checked my fuses (all good) so assumed it was dead alternator. Put in a new one - still no charging to battery. Assumed it was dead regulator. Put in a new one - still no charging.
Any ideas? Brand new alt belt too, good and tight.
I noticed my new battery seemed to be getting tired, and while running tested the voltage at the POS & NEG and found it just under 12V. Made sure wiring was all intact at alternator and regulator (rather a quick glance and push on 4-wire connector at regulator) and checked my fuses (all good) so assumed it was dead alternator. Put in a new one - still no charging to battery. Assumed it was dead regulator. Put in a new one - still no charging. I attached a couple pics of the regulator incase I screwed something up; but not sure what can be screwed up. The 4-wire connector only goes in one way. The round/tubular ...resonator or radio noise suppressor is connected to the wire that comes up from engine harness with the rubber connector - pretty sure I put that back on properly. Is there a fuse somewhere?
Any ideas? Brand new alt belt too, good and tight.
My very first inclination would suggest you thoroughly clean your ground connections - ground to engine block (most important) then ground to chassis/frame (top metal plate near radiator shroud) - should be a wire off the negative battery post which goes to the chassis/frame. Thoroughly clean (e.g. wire brush, pocket knife, sandpaper, whatever) the metal and the cable end terminals. You can also perform a voltage drop test &/or measure ground via a multimeter.
My very first inclination would suggest you thoroughly clean your ground connections - ground to engine block (most important) then ground to chassis/frame (top metal plate near radiator shroud) - should be a wire off the negative battery post which goes to the chassis/frame. Thoroughly clean (e.g. wire brush, pocket knife, sandpaper, whatever) the metal and the cable end terminals. You can also perform a voltage drop test &/or measure ground via a multimeter.
That sounds like a great path to pursue, thank you. Amazing how many problems get traced back to bad ground. (Wish I had thought about this about 3 days ago - before I bought new alternator and regulator, though probably was close to needing them anyways).
Check and clean grounds first and re-test.
If no charge, jumper terminals F and 3 on the regulator, if charge bad regulator. If no charge bad alternator or wiring problem.
Does the charging/alt lamp in the instrument cluster work?
Check and clean grounds first and re-test.
If no charge, jumper terminals F and 3 on the regulator, if charge bad regulator. If no charge bad alternator or wiring problem.
Does the charging/alt lamp in the instrument cluster work?
Good luck!!!
Is F ground and 3 12v "hot"? I'm not great with electricals but my brain tells me, if F is ground and 3 is hot than that's a short waiting ...so I must be wrong. So when I jump them, you're saying - if after that and I run the car if the battery is getting charged, then it's a bad regulator. If no charge, then bad alternator or wiring; right? Just weird where both alternator and regulator are brand new.
Which makes me think it's a bad ground. I'll get busy on that and report back. Thank you!!
Jumping F to 3 energizes the field in the alternator but it can't be left that way as it would overcharge. The F and 3 are stamped in the regulator plug,. IIRC it's dark blue wire to red wire.
Yes, if it charges when jumped the regulator is bad.
Jumping F to 3 energizes the field in the alternator but it can't be left that way as it would overcharge. The F and 3 are stamped in the regulator plug,. IIRC it's dark blue wire to red wire.
^x2^
If you suspect possibility of a bad cable, slicing into the outer insulation of the cable at each end will reveal if the cable exhibits corrosion. Significant corrosion could be the culprit. You want a nice tidy clean flow of electrons moving through the cable(s). Here's an example of a motorcycle cable I replaced after determining the cable itself was heavily corroded. You might not visualize this corrosion if you don't remove some insulation to witness.
Cable peeled away Corrosion Sliced cable to reveal corrosion Corrosion revealed Heavy corrosion yields increased resistance to electron flow
^x2^
If you suspect possibility of a bad cable, slicing into the outer insulation of the cable at each end will reveal if the cable exhibits corrosion. Significant corrosion could be the culprit. You want a nice tidy clean flow of electrons moving through the cable(s). Here's an example of a motorcycle cable I replaced after determining the cable itself was heavily corroded. You might not visualize this corrosion if you don't remove some insulation to witness.
Cable peeled away Corrosion Sliced cable to reveal corrosion Corrosion revealed Heavy corrosion yields increased resistance to electron flow
Thank you! I'll keep all this great info in mind as I go through checking my grounds and wiring itself.
On a vehicle of this age, which most likely demonstrates some rust & common corrosion of the chassis/frame and metal (block, firewall, etc.) areas, as you work your way through areas, take the time to remove cables and clean the posts, brackets, braces, electrical terminal ends, screws, nuts, bolts, etc. or replace those pieces of hardware. The alternator obtains its ground from the alternator bracket using the hardware to mount the bracket - the ground is provided via the block battery ground terminal. But, in general, you want a good hotbed of electron flow throughout your entire 51 year old metal beast. Electrons "flow" from the negative (-) anode battery post through all metal in the vehicle (block, frame/chassis, dash, firewall, etc.) and return "to" the positive (+) cathode battery post. Corrosion along the ground path (in particular and most importantly) will/can significantly increase resistance to electron flow - seriously inhibiting electrical components.
Have you checked voltage at the alternator OUTPUT post with engine running? That will tell you if it's an alternator problem or a voltage regulator problem. Less than 14.5vdc there, you have a bad alternator.
Check voltage at the junction block post with engine running. It should be same as at alternator output post. If not, VR or wiring problems. Likely a corroded wire or faulty fusible link.
Wiring diagram in your CSM will help here.
Also, and very important, make sure you have the correct alternator for the car. It's possible you've got hold of an internally regulated alternator which, combined with an external voltage regulator, will create all kinds of charging problems. If alternator's two-wire plug looks like | | it's an external regulator unit. If it looks like - - it's internally regulated.
Last edited by rocketraider; April 4th, 2023 at 07:43 AM.
^ I don't agree but am open to an explanation/learning moment...The voltage to the alternator regulated by the VR is what controls alternator output. The alternator will not produce a higher voltage output if the regulator isn't allowing it the correct voltage at the correct frequency/interval.
Have you checked voltage at the alternator OUTPUT post with engine running? That will tell you if it's an alternator problem or a voltage regulator problem. Less than 14.5vdc there, you have a bad alternator.
Check voltage at the junction block post with engine running. It should be same as at alternator output post. If not, VR or wiring problems. Likely a corroded wire or faulty fusible link.
Wiring diagram in your CSM will help here.
Also, and very important, make sure you have the correct alternator for the car. It's possible you've got hold of an internally regulated alternator which, combined with an external voltage regulator, will create all kinds of charging problems. If alternator's two-wire plug looks like | | it's an external regulator unit. If it looks like - - it's internally regulated.
I have an alternator with the two verticle connectors, not horizontal. I'm measuring 11.2 at the rear of the alternator output large red wire. FIRST THING I'M GOING TO DO IS CHECK ALL GROUNDS
Have you checked voltage at the alternator OUTPUT post with engine running? That will tell you if it's an alternator problem or a voltage regulator problem. Less than 14.5vdc there, you have a bad alternator.
Check voltage at the junction block post with engine running. It should be same as at alternator output post. If not, VR or wiring problems. Likely a corroded wire or faulty fusible link.
Wiring diagram in your CSM will help here.
Also, and very important, make sure you have the correct alternator for the car. It's possible you've got hold of an internally regulated alternator which, combined with an external voltage regulator, will create all kinds of charging problems. If alternator's two-wire plug looks like | | it's an external regulator unit. If it looks like - - it's internally regulated.
I spent an hour or so disconnecting battery, then disconnecting the wire off the NEG cable to ground by radiator - as well as taking off the alternator, alternator bracket, loosening power steering pump and bracket to loosen the big'*** NEG cable to block ground... Cleaned and wire brushed both areas very well, applied dialectric grease and retightened. The NEG cable connecting to battery is uber clean. Still having "no charge" issue at battery with brand new alternator and voltage regulator. Interestingly, when I got the new alternator and v regulator, the gentle glow of the "GEN" light in dash cluster went out. Now, after cleaning the grounds - it's back. When I rev the engine, it goes out.
Don't become reliant on new = good, test. Have seen many "new" defective parts, that's why new items come with a warranty in the event they are bad. Good luck!!!
Finally (since it's nearing my sleep time) & my golf tee-time is early morning - you do have a ground wire from the engine head to the firewall installed, correct? Review your wiring diagram and note where the VR obtains its ground. Good Luck & Good Night.
Relative to Post #5 - if you prefer to follow a video, this is the exact method to test if ALT is functioning (capable of putting out 14.3V minimum). https://youtu.be/N1JKKUfgCtk
Additionally, if you have a Rear Window Defogger - review Rob's post here >>> Post 3
Great video. When he's testing at the voltage regulator, and says "test here to see if you're getting power or 12V" or whatever he says at the 1:30 mark, he doesn't show which of the 4 wires he tests and shows he's getting 11.xx and then says "we are". Which wire did he measure? Bottom line, I can certainly disconnect my new voltage regulator and jump 1 & 3 and then - I assume - measure at the battery and see if it's getting 13.xx volts - ergo the alternator is charging it. I gather I can also measure the terminal in the back of the alternator where the large red wire is connected as that's where the "juice" flows from the alternator?
You first need to perform the jumper test as Sugar Bear has already suggested to see if your ALT is even capable of producing ~14V.
I found that there was no ground strap on the regulator. So I built one and loaded up with dielectric grease and attached to one of the frame braces in the engine bay and one of the regulator securing bolts. Made no difference in terms of registering anything more than 11.58 V at the battery. Did the jumper test between F and 3 and measured at battery again: 14.13V
I found that there was no ground strap on the regulator. So I built one and loaded up with dielectric grease and attached to one of the frame braces in the engine bay and one of the regulator securing bolts. Made no difference in terms of registering anything more than 11.58 V at the battery. Did the jumper test between F and 3 and measured at battery again: 14.13V
What the deuce???
Am I supposed to know what "What the deuce???" means. Sorry, I don't get it.
While you're at the parts store buying a new VR (see Post #5), grab some new sheet metal screws of various sizes & a new condenser, cleanup that firewall area where the VR mounts. Those rusty screws/bolts & bracket are creating an electrolytic corrosive nest. That should be cleaned up. The ground strap (Post #22) is supposed to be BIG & BEEFY (like a ground strap) and it's attached to the passenger side engine (the head I believe). You want a deep pool of electrons. Large pieces of metal with significant mass are your best ground sources - i.e. the engine. Might need use a flashlight to find the ground strap mount point on the engine.
Unfortunately, my 1972 PIM doesn't have the page demonstrating the engine ground strap location. So, I'm posting an image of my 1971 PIM engine ground strap location. It may not be exactly the same engine location, but it's going to be very close. Use a flashlight, it's kind of tough to see. You'll note there's a little difference where it says screw STRAP TO DASH (below) since '71 VR is not in the same location as the '72 VR. But as you can see in Post #22 (above) the ground strap end is attached to the VR bolt on the firewall.
Thank you. Just curious if there’s a way to test it on the bench, resistance from one pole to another or something. It is brand new but that obviously doesn’t mean anything.
I’ll be cleaning up the firewall where it mounts and getting a proper ground strap - making me think it may not be the VR but the stuff around.
Unfortunately, my 1972 PIM doesn't have the page demonstrating the engine ground strap location. So, I'm posting an image of my 1971 PIM engine ground strap location. It may not be exactly the same engine location, but it's going to be very close. Use a flashlight, it's kind of tough to see. You'll note there's a little difference where it says screw STRAP TO DASH (below) since '71 VR is not in the same location as the '72 VR. But as you can see in Post #22 (above) the ground strap end is attached to the VR bolt on the firewall.
Unfortunately, my 1972 PIM doesn't have the page demonstrating the engine ground strap location. So, I'm posting an image of my 1971 PIM engine ground strap location. It may not be exactly the same engine location, but it's going to be very close. Use a flashlight, it's kind of tough to see. You'll note there's a little difference where it says screw STRAP TO DASH (below) since '71 VR is not in the same location as the '72 VR. But as you can see in Post #22 (above) the ground strap end is attached to the VR bolt on the firewall.
One other question: (Sorry I’m not smart enough to know how potentially stupid this question is): Is it possible, when I installed a new starter, that I could have connected the two smaller gauge wires to the solenoid incorrectly? I know I got the massive POS cable correct (have to be an all time idiot to get that wrong). But I recall looking at the, IIRC, the white or yellow and the purple and going “the white one goes on this terminal and the purple goes on that one”. I will say that the new starter works just fine - so I assumed I “got it right” but just putting it out there as you all remotely help me.
Not a stupid question, actually a good one. If the yellow and purple wires are on separate terminals and the car starts and runs I'd say your good. Sorry but I don't remember which wire is outboard for sure and a guess would be useless. Another member will know for sure and respond.
One other question: (Sorry I’m not smart enough to know how potentially stupid this question is): Is it possible, when I installed a new starter, that I could have connected the two smaller gauge wires to the solenoid incorrectly? I know I got the massive POS cable correct (have to be an all time idiot to get that wrong). But I recall looking at the, IIRC, the white or yellow and the purple and going “the white one goes on this terminal and the purple goes on that one”.
The only stupid question is the question which never gets asked. Never be afraid to ask a question - never.
From the factory, your car had three wires on the starter, a battery cable to the large post on the solenoid, a purple wire to the "S" (for START) terminal, and a yellow wire to the "R" (for RESISTOR BYPASS) terminal.
Purple>S
Yellow>R
GREAT BIG WIRE>GREAT BIG POST
If the starter is working correctly, chances are you got it correct. Never hurts to double-check your work once you have confirmation.
You're collecting some decent illustrations. Here is the starter cable OEM wiring (1972 Oldsmobile Product Information Manual - PIM). At some point, you' be well-served to get a copy of the PIM.
April 3rd, 2023, 03:06 PM
