2002 Jaguar XK8 - Electrical Headache
#3
So, with car running, just after starting sending a dump of amps to the starter, that cable/wire is too hot to touch. Pos and Neg battery cables are not hot on the battery, no other bolt down connection on any of that mega fuse pack is hot. JUST that one in question, in the photo...
Is it that the section of exposed wire is so corroded that it is offering resistance to current? Heating up?
Is it that the section of exposed wire is so corroded that it is offering resistance to current? Heating up?
#4
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#8
I think my problem is going to be not having long enough leads on my DMM to touch both ends of the cable/wire at the same time... Don't know if I'll get an accurate reading if I use some kind of extender wire.
Sheeeesh... Expect the unexpected. As hot as that's getting it can't be driven this way. Thankfully I have 2 more junky cars I can drive, lolololololololol
Ive disconnected the battery and am going to clean up what I THINK is the other end of that cable in the engine bay. If someone could confirm that that pilar/ECU enclosure is the "other end" I would be super grateful.
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PKWise (09-01-2020)
#9
So, I took a measurement (I think) from the heavy wire that is attached to the ECU enclosure and the boot wore in question. Pretty sure I have my meter set up right (I ran it thru all settings) at 200ohms the lowest setting and got little if any resistance. That's with an extension wire that also read no resistance. Interesting... I will go back in and check for continuity between the two ends but I think I have it right.
The bolt down in the engine bay side of that cable/wire was not hot, either. Something is odd here...
Could the heat I'm feeling be a heat associated with the recharge of the battery after start up?
The mega fuse set up (not wires and cables which are OE) and fuses are fairly new, within a year.
Reading across battery terminals, cables off, car off, is 12.6 12.7...
The bolt down in the engine bay side of that cable/wire was not hot, either. Something is odd here...
Could the heat I'm feeling be a heat associated with the recharge of the battery after start up?
The mega fuse set up (not wires and cables which are OE) and fuses are fairly new, within a year.
Reading across battery terminals, cables off, car off, is 12.6 12.7...
#12
SOLVED!
So,,, I hate counting chickens,,, but I think I solved my problem.
Dont know if there ever was one BUT I introduced a copper washer between the connector and the face of the mega fuse and the heating stopped and charge across the battery when running has increased. Needless to say I will be going in now and inserting a copper washer at all these little connection points in the mega fuse set up.
Damned-est thing.
Thanks good people!
Dont know if there ever was one BUT I introduced a copper washer between the connector and the face of the mega fuse and the heating stopped and charge across the battery when running has increased. Needless to say I will be going in now and inserting a copper washer at all these little connection points in the mega fuse set up.
Damned-est thing.
Thanks good people!
#13
The way I took NBCat's advice is to measure the resistance between the exposed copper wire in your photo and the connector also in your photo! The high resistance is likely to be in the crimping of the wire in that connector. Edit; Looks like you got there as I was posting!
Last edited by astromorg; 09-01-2020 at 12:58 PM.
#14
Count me WRONG
The way I took NBCat's advice is to measure the resistance between the exposed copper wire in your photo and the connector also in your photo! The high resistance is likely to be in the crimping of the wire in that connector. Edit; Looks like you got there as I was posting!
I will do ask you just suggested... But (and I have limited electrical knowledge) is that possible? Will the reading be only between that small section of wire and exclude the 10ft remaining? The section that heads forward to the engine compartment...? One sec, I'll go try.
Ok, you guys are RIGHT! If I use the probe and poke it thru the insulation of the cable just before that damaged section I get 14.20, 14.15... after, I get 13.6 13.7... I am losing voltage in that weird area of damage. If I pin the probe at the mega fuse getting 13.6,,, then I pinch and poke the damaged section of cable, it bounces around up to 14.15, down, up down...
When I measure at that post under the hood I get 14.15 - 14.20volts.
Do I need to replace this whole damn section of cable, thru the car and all? Repair, splice and make a connector and use the OE cable? Is a repair of cable of this sort possible?
Today was supposed to be light, lololol...
Oh these wonderful cars!
#16
Getting about 1 to 1.5 ohms of resistance in the short section of the longer cable.... Which I guess is a lot,,,, don't know how to break down expected heat product considering resistance and number of volts or amps. But, I guess this 1 - 2 ohms makes heat.
Question is,,, what now. That cable seems to run under the car. Don't know yet.
Question is,,, what now. That cable seems to run under the car. Don't know yet.
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michaelh (09-01-2020)
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+1 to both above
Looks like either the crimp slackened, some corrosion got in there or both.
If we conservatively assume a starter load current of at least 100A, then the heat produced (=watts) is 10,000 x R where R is the resistance in the joint. You can see that even a fraction of an ohm will result in a not inconsiderable warm-up.
If there is enough slack in the cable, cut it where it exits the existing connector, or clean the end as much as possible.
The problem with applying the amount of heat required to make the joint is that the insulation tends to shrink up the cable, so the heat-shrink sleeving is a good idea. Clean the excess flux afterwards.
Looks like either the crimp slackened, some corrosion got in there or both.
If we conservatively assume a starter load current of at least 100A, then the heat produced (=watts) is 10,000 x R where R is the resistance in the joint. You can see that even a fraction of an ohm will result in a not inconsiderable warm-up.
If there is enough slack in the cable, cut it where it exits the existing connector, or clean the end as much as possible.
The problem with applying the amount of heat required to make the joint is that the insulation tends to shrink up the cable, so the heat-shrink sleeving is a good idea. Clean the excess flux afterwards.
#20
+1 to both above
Looks like either the crimp slackened, some corrosion got in there or both.
If we conservatively assume a starter load current of at least 100A, then the heat produced (=watts) is 10,000 x R where R is the resistance in the joint. You can see that even a fraction of an ohm will result in a not inconsiderable warm-up.
If there is enough slack in the cable, cut it where it exits the existing connector, or clean the end as much as possible.
The problem with applying the amount of heat required to make the joint is that the insulation tends to shrink up the cable, so the heat-shrink sleeving is a good idea. Clean the excess flux afterwards.
Looks like either the crimp slackened, some corrosion got in there or both.
If we conservatively assume a starter load current of at least 100A, then the heat produced (=watts) is 10,000 x R where R is the resistance in the joint. You can see that even a fraction of an ohm will result in a not inconsiderable warm-up.
If there is enough slack in the cable, cut it where it exits the existing connector, or clean the end as much as possible.
The problem with applying the amount of heat required to make the joint is that the insulation tends to shrink up the cable, so the heat-shrink sleeving is a good idea. Clean the excess flux afterwards.
yes, it's remarkable... I've been cleaning up the existing wire/cable and voltages are going up and heat is down. This can't be long term, but she is my daily... I'm going to have to figure something out,,, make a salad dressing in the mean time... I'll report back in a minute...