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Sept 28, 2014 17:16:50 GMT
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Hi folks of Retro Rides. I need a bit of a knowledge check - I am suffering from flat batteries in my Jag. The garage I gave it to to do some work on the starter motor told me they thought the battery was on its way out as it tended to loose charge when left overnight. I hadn't had much trouble until I took it to the Goodwood Revival and came back to a flat battery at the end of the day. I changed the battery, and thought I would check the voltage across the battery with the engine running which gave me a figure of about 12.4v at idle, increasing to 12.6v when revved - my understanding is that it should be about 14v. The alternator looked a bit tired, and I had a spare in stock so I thought there was nothing to lose by replacing it. With the new alternator I get the same voltage readings. The ammeter in the car, has always pointed to mid way between charge and discharge when idling and swings a bit over to "charge" when revved, and does the same with the new battery and alternator. Am I right in thinking that the voltage across the battery should be 14v when running? As a little bit of extra information, at night with the dash lights off, there is a very slight glow from the charging light on the dash, when moving which seems to go away when the engine is idling! Any thoughts would be welcome! cheers Cortinaman
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Old Fords never die they just go sideways
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Rich
Club Retro Rides Member
Posts: 6,237
Club RR Member Number: 160
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strange charging light behaviour!Rich
@foxmcintyre
Club Retro Rides Member 160
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Sept 28, 2014 18:02:09 GMT
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Sounds like both Alternators have had it. Your charge rate is far too low. It would be worth checking all the connections to the battery an the connections to the warning lamp however.
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Sept 28, 2014 18:05:12 GMT
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You want to be charging at 14.4, you can settle for 13 but less than that means your alternator is buggered
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Sept 28, 2014 18:23:58 GMT
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thanks for the replies chaps - I was pretty sure the voltage should be 14ish volts if all was well. I'll check all the earths, connections etc, before I stump up for a new alternator, as it was new and never used! Is there any way to check what the alternator is actually producing i.e. voltmeter directly to the plug on the alternator? cheers Cortinaman
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Old Fords never die they just go sideways
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Sept 28, 2014 19:02:12 GMT
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The cable that connects the alternator to the battery. Measure from the STUD on the alternator to the battery terminal. This will give you the correct reading. Also, you could use a clamp ammeter to measure the current output.
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Sept 28, 2014 19:25:06 GMT
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thanks for that reida1994, what do you mean by the "STUD" on the alternator - mine has a three spade connector type plug on the back?
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Old Fords never die they just go sideways
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93fxdl
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Sept 28, 2014 19:47:06 GMT
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Occasionaly can get a situation where battery is fully charged, so will not take any more, try testing again with lights, heated screen etc on Ttfn Glenn
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Sept 28, 2014 19:57:49 GMT
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Occasionaly can get a situation where battery is fully charged, so will not take any more, try testing again with lights, heated screen etc on Ttfn Glenn Cheers Glenn, I'll give that a try.
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Old Fords never die they just go sideways
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Sept 28, 2014 20:47:04 GMT
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Then you will need to measure from the connection. I said stud, because a lot of cars have a cable on a stud, people often try measuring from the nut, when it's the stud that you need to measure from.
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Sept 28, 2014 21:04:24 GMT
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Then you will need to measure from the connection. I said stud, because a lot of cars have a cable on a stud, people often try measuring from the nut, when it's the stud that you need to measure from. Cheers for that, I'll give it a try.
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Old Fords never die they just go sideways
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sparkyt
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selling stuff
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Sept 28, 2014 21:10:38 GMT
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May sound daft but it's something that I missed in the past . My alternator had a smaller pulley on it than it should of . Seems somebody had changed it for another just before selling the car on ..
The Ault needs to be turning fast enough at idle to maintain the voltage ..
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Sept 28, 2014 22:12:00 GMT
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I'de check and recheck the condition of all the wiring involved, also (and this is very random) on my old Diesel Astra the brand new battery was stuffed, it would only accept about a 5amp maximum charge so would gradually go flat over the space of about a week or so, it was just luck figuring that one out as after changing 2 alternators, and rewiring I threw on an old battery one day that I knew was on its last legs and lo and behold problem solved.
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Rich
Club Retro Rides Member
Posts: 6,237
Club RR Member Number: 160
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strange charging light behaviour!Rich
@foxmcintyre
Club Retro Rides Member 160
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Sept 28, 2014 22:14:52 GMT
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Occasionaly can get a situation where battery is fully charged, so will not take any more, try testing again with lights, heated screen etc on Ttfn Glenn Err, no. The voltage will still read at 14v for a healthy charging system regardless of the state of charge of the battery. If the alternator is showing 12V it's generating 12V, which isn't enough to keep a battery charged.
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Copey
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Sept 28, 2014 22:48:32 GMT
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Occasionaly can get a situation where battery is fully charged, so will not take any more, try testing again with lights, heated screen etc on Ttfn Glenn Err, no. The voltage will still read at 14v for a healthy charging system regardless of the state of charge of the battery. If the alternator is showing 12V it's generating 12V, which isn't enough to keep a battery charged. agreed, i have a permanent voltage meter hooked up in my Saph and its always on somewhere between 13.8 and 14.2 depending on what lights are on, with the engine running i have never seen it drop anywhere near 12
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1990 Ford Sierra Sapphire GLSi with 2.0 Zetec 1985 Ford Capri 3.0 (was a 2.0 Laser originally)
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Sept 29, 2014 8:01:45 GMT
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find a little elec repair back street place , they will test the alt for next to nothing and be able to sell you the bits to fix it
on all my old cars i get some 4 gauge cable and some ends and replace the big three as its called...new starter , alternator and battery cable , and fresh earths everywhere i can see , seems to help alot
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91 golf g60, 89 golf 16v , 88 polo breadvan
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Sept 29, 2014 10:21:29 GMT
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Not sure if it's relevant to you but I was having alternator issues - battery running out of charge whilst actually driving and whilst standing - earlier in the year due to relocating my battery to the boot. (Not sure if your battery is in the original location)
I resolved the issue when I ran an additional 25mm2 cable (fused) directly from the alternator output stud to the + battery post.
So similar to SteveOs post above.
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93fxdl
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Sept 29, 2014 16:11:41 GMT
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Err, no. The voltage will still read at 14v for a healthy charging system regardless of the state of charge of the battery. If the alternator is showing 12V it's generating 12V, which isn't enough to keep a battery charged. agreed, i have a permanent voltage meter hooked up in my Saph and its always on somewhere between 13.8 and 14.2 depending on what lights are on, with the engine running i have never seen it drop anywhere near 12 I was going on the slightly glowing charge light Ttfn Glenn
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Rich
Club Retro Rides Member
Posts: 6,237
Club RR Member Number: 160
Member is Online
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strange charging light behaviour!Rich
@foxmcintyre
Club Retro Rides Member 160
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Sept 29, 2014 18:25:57 GMT
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agreed, i have a permanent voltage meter hooked up in my Saph and its always on somewhere between 13.8 and 14.2 depending on what lights are on, with the engine running i have never seen it drop anywhere near 12 I was going on the slightly glowing charge light Ttfn Glenn Which would indicate the charging system isn't functioning correctly. Not that the battery is 'fully charged'
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Thanks for all the advice folks - I now just need to find some time to work on the car!! Not sure if it's relevant to you but I was having alternator issues - battery running out of charge whilst actually driving and whilst standing - earlier in the year due to relocating my battery to the boot. (Not sure if your battery is in the original location) I resolved the issue when I ran an additional 25mm2 cable (fused) directly from the alternator output stud to the + battery post. So similar to SteveOs post above. Freshandminty - do you remember what rating of fuse you used when you ran the additional cable? cheers Cortinaman
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Old Fords never die they just go sideways
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Thanks for all the advice folks - I now just need to find some time to work on the car!! Not sure if it's relevant to you but I was having alternator issues - battery running out of charge whilst actually driving and whilst standing - earlier in the year due to relocating my battery to the boot. (Not sure if your battery is in the original location) I resolved the issue when I ran an additional 25mm2 cable (fused) directly from the alternator output stud to the + battery post. So similar to SteveOs post above. Freshandminty - do you remember what rating of fuse you used when you ran the additional cable? cheers Cortinaman My alternator is rated at 90amp so I used a 100amp fuse, not sure if that's the right science behind it but it popped when i accidentally shorted it when removing a manifold heat shield so does the job right, and has been working fine in normal life since May.
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