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700/900 Series General Forum for the Volvo 740, 760, 780, 940, 960 & S/V90 cars |
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Intermittent death - lots of potential causes checkedViews : 4072 Replies : 75Users Viewing This Thread : |
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May 18th, 2022, 18:22 | #11 |
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Following on from Laird Sooby's point about broken earth cables, it might be informative to try connecting the battery negative pole to the engine block with a jump lead. If this improves things, it more or less proves there is a faulty earth somewhere.
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May 18th, 2022, 18:59 | #12 |
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That's common diagnostic practice during a charging investigation/diagnosis but in this case where it's also not starting would certainly be a worthwhile pointer!
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May 19th, 2022, 20:19 | #13 | |
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There is more than one cable attached to the clamp and as well as the clamp secured to the post there is a secondary arrangement which can if loose cause the engine to die as this has happened to me while travelling at 60 mph l blew my horn at a cyclist and it was enough to break contact on the battery post. Took a while to sus too.....worth a look. |
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May 19th, 2022, 20:23 | #14 |
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Those pesky cyclists cause all sorts of problems, don't they Andy?
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May 19th, 2022, 21:23 | #15 | |
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he was one of those guys that assumed that he owned the road up to the white line out in the open countryside on a double centre white line. Problems began after l blew the horn the engine died and l coasted to a stop only for him to cycle past me........................... |
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May 19th, 2022, 22:34 | #16 | |
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They view any overt attempt at communication as aggessive (whether it is or not) and use that (assumed) negative energy to invoke gremlins to attack your vehicle and/or you. They should never be trusted and certainly never communicated with! I thought it was just me and i'd been unlucky having encountered a one-off Voodoo Cyclist but you are the latest in a long line of many that has confirmed similar experiences. Last one i encountered caused the output cable from the alternator to break away from the crimp terminal on the back of the alternator on my last 740GLE. Late at night (~2330 hrs), car trailer on the back with a Rover 827 Coupe on it and the headlights start getting dim about 6 miles from home. They'd not been right for a while by then but with the lighting on the motorway/dual carriageway and lighting from others on the A roads it hadn't really been noticeable. A USA spec car pulled out of the road i was going to turn into soon and his left-hand-drive headlamps dazzled me so i touched the brakes to reduce my speed so i could see enough of the road to continue safely. That was enough to stop the fuel pumps which killed the engine and i coasted into a lay-by. After a very long day (and only vaguely remembering the cyclist on the roundabout in Milton Keynes that had cut me up) i didn't think of the obvious but my passenger did - swap the battery from the Coupe into the 745 and get home that way. Meanwhile that cyclist in MK thought he got one over on me!
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May 20th, 2022, 13:54 | #17 |
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Ideally yes, but its not "bad" either, possibly a higher load test with high beam would drop it further closer to 13V which you could then deem as bad. The loom does gradually increase in resistance with corroded compression connections. Most cars work fine with a bit of resistance, but gradually they will run into slow charging + short journerys and battery damage and dim lights.
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May 20th, 2022, 14:23 | #18 |
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13.8 v
13.8 V shows that in any case the alternator is charging, otherwise the voltage measured directly at the battery terminals would be closer to 12 V.
It does not explain however, the sudden voltage drop to 5V or slow drainage of the battery. If all the electric connections are in order, it would take quite a heavy load (closer to a shortcut) for the battery voltage to drop from 12 to 5V. That would not go unnoticed. It is therefore more likely that somewhere an electrical connection is intermittently failing. Crucial is to know where this 5V is measured. After the battery has had time to "recover", does it crank normally or is the starter motor barely turning over? |
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May 23rd, 2022, 09:04 | #19 |
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Dear Chums,
An update. I have the Volvo back. The man who has fixed it says he cannot replicate the fault. He has checked the car is charging the battery and not draining it even with full beam on, cooling fan on, adjusting electric seats and dropping all 4 windows at once. He said the car is most definitely healthy in terms of its ability to charge up. What did he find and what did he do? He cleaned negative batt terminal, removed any earth cable cleaned where it bolts down and re-attached. This included starter and alternator cables. He made a long list of voltages and resistances once he had done this, explaining he was happy with what he had achieved. He 'remade' one earth cable and in his cleaning and tightening regime he found two were a bit loose which would explain intermittent fault and why car was sometimes dead as a doornail and at other times, willing to start after being left or crucially towed which may have jiggled the earth back into contact. As it is, I have done things that would have rendered it 'dead' (5v) like leaving the door open, adjusting seats with only ignition on etc and it starts first crank. Another situation that has caused significant misbehaviour previously, heavy rain, has not had any adverse effect. The chap that fixed it is very pleased that the car is over 200k mi and in use. He also liked the roof rack. He said he cannot guarantee that it is fixed but has spotted and rectified a few things he believes could have been intermittently problematic. Thanks for all the input and willingness to help. I will come back in 1 month to say everything is fine or before if it isn't. P.S. I now owe this car a bit more TLC. Camshaft oil seals are weepy which in turn drip onto water pump seal, eating it. Even though not due a cambelt yet, I will do that whilst in there (is there a forum locking tool doing the rounds?). Not sure if diff oil has ever been done so will do that (always undo top first in case it doesn't undo once you've drained diff). But most importantly, I will just keep using it. |
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May 23rd, 2022, 17:31 | #20 | |
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