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Old 03-06-2021, 02:08 PM   #1
Bcmonks
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Default 1982 Volvo 240 - Low Voltage

Hello,

I was driving my 240 back from work yesterday and noticed that the Turbo, Battery, Brake Failure, Parking Brake, and Sombda? (Can't remember the exact name of that last one) All came on and my voltage was reading right on the red line. Weirdly the headlights did not seem dim though.

I got home fine and went to check the battery and it read 12.2V. I had my wife start it while looking at the voltage of the battery and it dropped to ~11.5V and didn't go back up after about 15 seconds, and it also started with no issue.

Does anyone know what this could be? I believe I had the brushes replaced in the Alternator maybe 5 years ago. I checked the battery terminals and the connections seem tight; I'm just hoping it's something I can fix over the weekend as my other car is dead in the water due to a bad transmission, and this is my only transportation to and from work.
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Old 03-06-2021, 04:43 PM   #2
dl242gt
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Your alternator or the wiring is the problem. You want to make sure the small red wire is feeding 12v to the alternator to 'excite' the alternator to charge. Also there is a case ground wire that goes from a stud on the back of the alternator to the engine. If either of those circuits are bad you won't get the alternator to charge. Use a test light to check that the small red wire lights up the test light. You can put the clip on the alternator case and touch the large red to test that the ground is good. If the wiring checks out. Then it's the alternator itself.
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1982 242 turbo. 338k miles. MVP coilovers and 3" exhaust. Flowed 405 with a V15. Cossie turbine housing with upgraded compressor housing. 90+, IPD remote oil filter. Some other goodness, too. Been lots of fun over 25 years. Restored in 2k. Now ready for a 2nd restoration.

1993 245 Classic, 430k miles, enem V15. IPD bars and chassis braces. Simons sport exhaust from Scandix. sbabbs ezk chip. Been a good road warrior. Genuine Volvo rebuilt leaky M47.
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Old 03-06-2021, 07:01 PM   #3
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Quote:
Originally Posted by dl242gt View Post
Your alternator or the wiring is the problem. You want to make sure the small red wire is feeding 12v to the alternator to 'excite' the alternator to charge. Also there is a case ground wire that goes from a stud on the back of the alternator to the engine. If either of those circuits are bad you won't get the alternator to charge. Use a test light to check that the small red wire lights up the test light. You can put the clip on the alternator case and touch the large red to test that the ground is good. If the wiring checks out. Then it's the alternator itself.
I tested the ground and it seemed good, but for the life of me I can't figure out how to fit the test light in to test the exciter wire. I have a turbo right above it so I can't come in from above, and right behind the alternator is the oil filter, then below it seems to be the axle and associated bits which aren't giving me enough clearance to put the test light in there. I tried pulling out the wire, but it either doesn't come out, or I can't get enough grip on it to make it come out. Is there another way to check the excite wire?

Also, I checked my battery before doing this work and it was back at 12.2V

Unrelated, but might be related. I noticed a pretty good amount of green liquid (assuming coolant) around the alternator but not on it. It was on the alternator wires as they were touching the engine though. Unsure where that coolant is coming from but I'm not sure if that's related to this issue at all; thought I should add that just in case.

EDIT: I also just tried tightening the alternator belt as a little bit ago I did replace my timing belt. I'm not sure if it got any tighter, but it doesn't seem too loose. Definitely couldn't come off of the track but not as tight as the belt between the crank and AC pulley.

Last edited by Bcmonks; 03-06-2021 at 09:56 PM..
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Old 03-06-2021, 10:37 PM   #4
carver
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Check the brushes before you do anything else. When they get worn down you'll experience that kind of behavior. Cheap fix.

Quote:
Originally Posted by Bcmonks View Post
Hello,

I was driving my 240 back from work yesterday and noticed that the Turbo, Battery, Brake Failure, Parking Brake, and Sombda? (Can't remember the exact name of that last one) All came on and my voltage was reading right on the red line. Weirdly the headlights did not seem dim though.

I got home fine and went to check the battery and it read 12.2V. I had my wife start it while looking at the voltage of the battery and it dropped to ~11.5V and didn't go back up after about 15 seconds, and it also started with no issue.

Does anyone know what this could be? I believe I had the brushes replaced in the Alternator maybe 5 years ago. I checked the battery terminals and the connections seem tight; I'm just hoping it's something I can fix over the weekend as my other car is dead in the water due to a bad transmission, and this is my only transportation to and from work.
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Old 03-07-2021, 03:49 PM   #5
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Check the brushes before you do anything else. When they get worn down you'll experience that kind of behavior. Cheap fix.
Okay I took the brushes out, do these look bad? It looks like the left one is a lot shorter than the other one.

Last edited by Bcmonks; 03-07-2021 at 03:55 PM..
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Old 03-07-2021, 05:30 PM   #6
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The length looks fine. Usually they start losing good contact at about 5mm (less than half of your pic).

If you also have a battery light, it only comes on if you have a good connection from brushes to alternator AND it's not charging. If the brushes just lose contact, no light.

It's quite possible that after wearing out the previous brushes, then popping in new ones for another 5 years, that the copper slip rings that the brushes ride against are worn down to nothing. Peek inside the alternator hole where the brushes go and see what they look like.

Here'a a typical "new vs old" pic.

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Old 03-07-2021, 06:11 PM   #7
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The length looks fine. Usually they start losing good contact at about 5mm (less than half of your pic).

If you also have a battery light, it only comes on if you have a good connection from brushes to alternator AND it's not charging. If the brushes just lose contact, no light.

It's quite possible that after wearing out the previous brushes, then popping in new ones for another 5 years, that the copper slip rings that the brushes ride against are worn down to nothing. Peek inside the alternator hole where the brushes go and see what they look like.

Here'a a typical "new vs old" pic.

It doesn't look too bad:




Also I was able to check the exciter wire, with the Key in the II position, the test light turned on. It was harder to test than the ground as the wire went almost into the alternator instead of a nut on the top, sort of like this one:



I recently changed my timing belt, could that be it? The belt to the Alternator seems to have a little slack if I push on it, but I'm unsure if that's okay or not.
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Old 03-07-2021, 09:27 PM   #8
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You could take it to a car parts store and ask them to check the alternator to verify whether the problem lies with the alternator or elsewhere.
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Old 03-08-2021, 12:43 PM   #9
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Default Voltage drop test

Run the engine and put a meter on DC V and one lead to the alt case and the other lead to clean engine metal (like the intake) The reading should be less than 0.2V. ---------Higher=bad alt ground.
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