Caterham 7 repeated total electrical failure, after 2 miles
Discussion
Put this up on PH some weeks ago, and it seems to be some kind of earth fault. The car starts and runs normally but each time it is taken out on the road it suffers a total electrical failure after about 2 miles of driving. I have checked and remade all of the earth connections (not just those at the battery which has 12.9 volts when checked with the multi meter), at which point the car normally runs again, and it will run indefinitely including being revved when on the drive, but take it out on the road and it gives up after about two miles, No lights, no hazard flashers, no horn or heater motor, or windscreen wipers etc just totally dead as a door nail.
I have cleaned and re made the all the earth connections several times, and checked them for electrical continuity, and have not found any problems with any of them. My only guess is that it might be a break in a wire, which pulls together when the car is cold, but when it heats up, the sheathing expands and pulls the wire apart, but because the car runs indefinitely on the drive it may not be down to just heat either, Since absolutely everything cuts out, so that not even the side lights will come on, it seems to be some kind of major fault with one of the earths, or the earth wires. If anyone has any suggestions as to what the problem might be, or have had something similar happen to them, and found a fix for it I would much appreciate any advice they might have on the subject.
I have cleaned and re made the all the earth connections several times, and checked them for electrical continuity, and have not found any problems with any of them. My only guess is that it might be a break in a wire, which pulls together when the car is cold, but when it heats up, the sheathing expands and pulls the wire apart, but because the car runs indefinitely on the drive it may not be down to just heat either, Since absolutely everything cuts out, so that not even the side lights will come on, it seems to be some kind of major fault with one of the earths, or the earth wires. If anyone has any suggestions as to what the problem might be, or have had something similar happen to them, and found a fix for it I would much appreciate any advice they might have on the subject.
I had a very similar fault.
In my case it was the +12V connection(s) at the rear of the starter motor. They were barely hanging on and when moved with the car on the road caused it to cut out. Standing still it was fine.
Try checking all of the positive connections as well as the earths.
In my case it was the +12V connection(s) at the rear of the starter motor. They were barely hanging on and when moved with the car on the road caused it to cut out. Standing still it was fine.
Try checking all of the positive connections as well as the earths.
It's obviously something pretty major on the main battery/earth connections.
I once had identical symptoms on a Westfield, which I eventually (after much checking of connections and scratching of head) turned out to be the main cable from the battery to the starer motor had broken internally - the wires in the conductive metal core had broken, but the insulating PVC sleeve remained perfectly intact, so it was very difficult to spot - even when you tested continuity with a multimeter, it came up OK until you wiggled the cable about a bit.
Not saying that it will turn out to be the same problem for you, but clearly it's something simple, and major, enough to either stop all power getting from the battery to the fuse box, or all earthing between the battery negative terminal and the chassis (individual components are earthed separately, so it can't be further down the chain than the main battery-chassis earth).
I once had identical symptoms on a Westfield, which I eventually (after much checking of connections and scratching of head) turned out to be the main cable from the battery to the starer motor had broken internally - the wires in the conductive metal core had broken, but the insulating PVC sleeve remained perfectly intact, so it was very difficult to spot - even when you tested continuity with a multimeter, it came up OK until you wiggled the cable about a bit.
Not saying that it will turn out to be the same problem for you, but clearly it's something simple, and major, enough to either stop all power getting from the battery to the fuse box, or all earthing between the battery negative terminal and the chassis (individual components are earthed separately, so it can't be further down the chain than the main battery-chassis earth).
Thank you for your replies. They are much appreciated. As the fault results in a complete failure of the electrical system, I agree, that the fault is both major, (as no power even gets to the lights and hazard flashers) which hope fully should make it easier to locate as the main connections to the battery seem to be where the problem will lie. I did remake the positive and negative connections, and the battery has 12.9 volts so the most likely culprit will be the main leads coming away from the battery.
If I find the problem I will post what I found, but again thank you for your comments.
If I find the problem I will post what I found, but again thank you for your comments.
It would help to know the age of the car. If it is an early (ish) metric chassis then the wiring for the rear wheel speed sensor can cause problems that far out way it's own importance. Although that usually blows fuses, it may just be tripping the immobilizer. I would suggest disconnecting it and see if it helps.
DCL said:
It would help to know the age of the car. If it is an early (ish) metric chassis then the wiring for the rear wheel speed sensor can cause problems that far out way it's own importance. Although that usually blows fuses, it may just be tripping the immobilizer. I would suggest disconnecting it and see if it helps.
Thank you for your reply. the car is a 1989 chassis, and has no rear wheel speed sensor, just the usual geared drive off the transmission tail shaft. The fuse board is also a basic item with ten fuses (all OK) and 3 plug in modules for the horn, flashers, and auxiliary cooling fan. The total loss of electrical supply, is leading me to believe the fault lies with the main leads from the battery (which as stated before holds a charges of 12.9 volts, Even the sidelights and hazard flashers (which technically should remain usable even when the car is disabled) also fail to come on, it is as if there is no electrical supply whatsoever in the car, and as though someone had completely taken the battery out of the car, Even if the battery was dead (which it isn't) the alternator would supply enough power to run the electrical and ignition systems, whilst the engine was running but the car just cuts completely, so I will focus on the main connections to the battery
downsman said:
This may well be wrong, but if all the major positive and negative cables turn out to be OK, it might be worth trying a different battery. It's just possible there could be an internal fault despite the voltage being OK.
Again thank you all for your replies.The problem could be with the battery, but its nature is still baffling. having re made all the earth terminals (several times). the car will start and run normally, with everything working as it should, but when I take the car on the road for a test run, it will go about 2 miles, at which point all the electrical energy (in the car, (but not necessarily the battery) simply disappears, and it is as if there is no electricity in the car whatsoever, as if the battery had been removed from the vehicle. This in itself is strange, because even if the battery dies completely, with the engine running, there would still be electrical power being generated by the alternator sufficient to keep the ignition and all the electrical circuits working, but it does not, there is absolutely no electricity in the vehicle, even with the battery itself showing it has 12.9 volts . This one has really got me stumped, I will probably have to try an auto electrician who may be able to set equipment up which identifies what is happening at the time the electricity completely leaves the vehicle, but why does it only do this after two miles running on the road, but not when the car is running for over half an hour on the driveway?
In terms of what is different between driving the car and it sitting still is probably the battery. What are the fluid levels like in it? 12.9 volts, although not flat, is not what you'd expect on a full charged battery (charges at ~14.4 volts and should hold nearer 14 volts for a while after a run).
The car's ECU will shut down the engine if voltage drops to around 9 volts IIRC. So one possibility is that voltage is dropping to a level that stops the car after 2 miles. For the cost of someone looking at the car, you may want to try another battery first. A battery can developing an internal fault (perhaps a cell is going short circuit), and that may sorts itself out when it is not shaken about. I'd also check the alternator is working correctly ie not overcharging, or undercharging.
The car's ECU will shut down the engine if voltage drops to around 9 volts IIRC. So one possibility is that voltage is dropping to a level that stops the car after 2 miles. For the cost of someone looking at the car, you may want to try another battery first. A battery can developing an internal fault (perhaps a cell is going short circuit), and that may sorts itself out when it is not shaken about. I'd also check the alternator is working correctly ie not overcharging, or undercharging.
Thanks again for the latest replies. All the leads to and from the battery have been checked, and are all sound, and all the grounds have been cleaned and re made several times. It could quite possibly be the battery which has an internal fault, which only shows when the car is on the road and being charged at normal rate from the alternator, and get to a point where it breaks the continuity of the electrical supply to a point where no current is able to pass through it, resulting in the total failure of the electrical supply to the vehicle. I will have to look at the ways I can test the battery to try to determine if there is a fault. It is strange, because when the electrical supply is available there is so much power it spins the engine over rapidly on the starter, and the cars starts instantly. I will as promised post up what I eventually find (IF I do!) and thank you all for you appreciated comments. P.S the car does not have anything so advanced as an ECU, which may in the long run be a help in determining the problem!
I had this same problem with a V12 Jag, took it to a few specialists, none could solve it.
I walked in a car battery shop to buy a battery for another car and started to tell him about the problem.
He stopped me and said something along the lines of " is it a Unipart bla bla bla battery?"
Yes why I said. They fracture inside and started to go intermittent.
New battery and car was fine.
I walked in a car battery shop to buy a battery for another car and started to tell him about the problem.
He stopped me and said something along the lines of " is it a Unipart bla bla bla battery?"
Yes why I said. They fracture inside and started to go intermittent.
New battery and car was fine.
tight fart said:
I had this same problem with a V12 Jag, took it to a few specialists, none could solve it.
I walked in a car battery shop to buy a battery for another car and started to tell him about the problem.
He stopped me and said something along the lines of " is it a Unipart bla bla bla battery?"
Yes why I said. They fracture inside and started to go intermittent.
New battery and car was fine.
Since I have checked al the leads, circuits etc, and remade all the earths etc, I am starting to think along this line too. If every thing else has been checked and seems to be fine, I am guessing an internal fault in the battery, is about the only thing left which might be causing the problem I am experiencing.I walked in a car battery shop to buy a battery for another car and started to tell him about the problem.
He stopped me and said something along the lines of " is it a Unipart bla bla bla battery?"
Yes why I said. They fracture inside and started to go intermittent.
New battery and car was fine.
I will put in a new battery, as the last resort (that I can use) before engaging an auto electrician, since its cost will likely be less than the call out fee for an auto electrician. the worst that could happen is that I will end up with two batteries for the car. Thank you for your help.
Having now re made all of the earth terminals, and checked the main cables to and from the battery one more time, plus again checking that the battery is in good condition, the problem seems to have been rectified, and the car is running normally again.
The good thing about the failure being a total absence of electricity in the car, where not even the hazard flashers, or side lights would work, meant that whilst being a major failure in the electrics it really had to be something wrong with the earths owing to the total absence of electrical power,
I took off and checked each main cable for continuity, and because the cables were fairly generous in length, I was able to cut the ends off, and re solder new end terminals to each main cable. I also ground the lands where the cables attach to the engine block and chassis, The car now starts instantly, (it always did anyway) but more importantly it now continues to run, instead of failing completely after circa two miles on the road.
Just to say thank you for all your comments, there were all much appreciated.
The good thing about the failure being a total absence of electricity in the car, where not even the hazard flashers, or side lights would work, meant that whilst being a major failure in the electrics it really had to be something wrong with the earths owing to the total absence of electrical power,
I took off and checked each main cable for continuity, and because the cables were fairly generous in length, I was able to cut the ends off, and re solder new end terminals to each main cable. I also ground the lands where the cables attach to the engine block and chassis, The car now starts instantly, (it always did anyway) but more importantly it now continues to run, instead of failing completely after circa two miles on the road.
Just to say thank you for all your comments, there were all much appreciated.
Good to see you may have fixed it, but just one thing, you state that you have checked all of the earth connections, does this include the earths that use the wiper motor bracket?, easily forgotten as you really need to remove the scuttle to check. The reason I ask is that's where my problem was, and like yours nothing worked when it failed.
Tazio77 said:
Good to see you may have fixed it, but just one thing, you state that you have checked all of the earth connections, does this include the earths that use the wiper motor bracket?, easily forgotten as you really need to remove the scuttle to check. The reason I ask is that's where my problem was, and like yours nothing worked when it failed.
Hi there. The main connections to the battery on my particular chassis are as follows. The battery negative cable is fixed to a terminal secured to one of the engine mounting bracket bolts, The battery positive cable runs directly to the starter motor. A further heavy cable runs from one of the bolts which secure the clutch bell housing to the engine block to the bolt that secures the brake light switch to the chassis. As posted I re made these several times, after which the car would start instantly and run normally whilst on the drive, but would lose all its electrical power, after a circa 1 -2 mile run on the road.As the cables were all of sufficient length, I cut the existing terminals off them, and re made them with new terminals at each end of each cable. the car now starts instantly as it always did, but now keeps on running for longer than the 1-2 miles it was completely failing at before. It may have to run for a good few miles before I can completely trust it, but (so far
it appears to be running properly again. All comments I have received on this have been much appreciated so thank you all once again.. Gassing Station | Caterham | Top of Page | What's New | My Stuff