Voltage problems
Discussion
I’m still getting intermittent voltage level problems. They only occur when the car is hot (90+) and after the fans have kicked in at least once. However I’m not convinced it is all attributed to the fans running because today I move the car off the drive while it was still warm and the voltage dropped but the fans were defiantly not on.
Any thoughts ?
I’m thinking it could be the diode pack in the alternator breaking down under the heat and load maybe ?
I’m going to go over all the earth points when I get chance this week but what about this fusible link to the alternator. If this is bust then surely I’d get the ignition light all the time ?
Any thoughts ?
I’m thinking it could be the diode pack in the alternator breaking down under the heat and load maybe ?
I’m going to go over all the earth points when I get chance this week but what about this fusible link to the alternator. If this is bust then surely I’d get the ignition light all the time ?
RAW-SEWedge said:
ut what about this fusible link to the alternator. If this is bust then surely I’d get the ignition light all the time ?
The fuse link can crack at either end due to vibation.
It's an 'I' shape, where the mounting screws go through the top & bottom of the 'I', hence it cracks at the ends of the thin bit.
Once it's cracked contact is lost/remade as the bits vibrate around. This causes arcing to the ends of the broken bits & will eventually cause total failure.
Easy to check/replace, it's in a plastic housing underneath the offside engine mount, new one is appx 75p.
Had the front of the car up and removed the OSF wheel to have a look at the earths and the fusible link. I’ve checked the length of the cable under the engine mount from the starter to the alternator and there is no black box with a fuse in it ? The cabling runs uninterrupted from the back of the starter motor to the back of the alternator.
Am I looking in the wrong place or was this possibly a later addition that I haven’t got.
Am I looking in the wrong place or was this possibly a later addition that I haven’t got.
I can not find your original post, so.What voltage do you see, do for instance,the lights dim in sympathy? My old 390 did funny things and was the poor earth connection between the alternator and the mounting.It would only show sometimes and a good old scrape of both surfaces sorted it. A test would be, start engine and turn on everything, then take a screwdriver and see if the lights lit up brighter, when you scrape between the alternator and the mounting. Of course this could be a complete waste of my one finger typing as its completely different.
shpub said:
the only real way to see it is grovelling under the car time.
I grovelled good with a torch and couldn't see it. Will have an other look tomorrow. If that's no good then it's on the earths in the transmission tunnel.
I was looking forward to working on the car but the most frustrating thing at the moment is I just want to use it. I wish what ever it is would just bust but knowing my luck it will bust in the middle of nowhere !
Sorry to drag this up again but I’ve still not solved this. I’ve had a look over the electrics and everything looks OK. There is no fuse link and the two earths on the front of the car look good. I haven’t checked the ones under the transmission tunnel yet as it looks like a right royal pain in the rear.
I’ve just got the car hot and parked on the drive. Stuck a meter across the alternator and it read just under 14v. So I waited for the fans to come on and put the headlights on full beam and for a bit it was fine then the voltage dropped on the meter in the car so I checked the voltage across the alternator and it was 12.5v which is the battery voltage.
This looks like the alternator is knackered to me what do you think?
Are they susceptible to the heat because it’s unbearably hot by the alternator with the exhaust right underneath and the fans blowing hot air on it to. This would explain why it only happens when the car is hot.
Any one made or seen a heat shield to protect the alternator from the exhaust heat. Think I may look at making one to deflect the heat away a bit in the future.
I’ve just got the car hot and parked on the drive. Stuck a meter across the alternator and it read just under 14v. So I waited for the fans to come on and put the headlights on full beam and for a bit it was fine then the voltage dropped on the meter in the car so I checked the voltage across the alternator and it was 12.5v which is the battery voltage.
This looks like the alternator is knackered to me what do you think?
Are they susceptible to the heat because it’s unbearably hot by the alternator with the exhaust right underneath and the fans blowing hot air on it to. This would explain why it only happens when the car is hot.
Any one made or seen a heat shield to protect the alternator from the exhaust heat. Think I may look at making one to deflect the heat away a bit in the future.
RAW-SEWedge said:
Stuck a meter across the alternator and it read just under 14v. So I waited for the fans to come on and put the headlights on full beam and for a bit it was fine then the voltage dropped on the meter in the car so I checked the voltage across the alternator and it was 12.5v which is the battery voltage.
This looks like the alternator is knackered to me what do you think?
Are they susceptible to the heat because it’s unbearably hot by the alternator with the exhaust right underneath and the fans blowing hot air on it to. This would explain why it only happens when the car is hot.
Any one made or seen a heat shield to protect the alternator from the exhaust heat. Think I may look at making one to deflect the heat away a bit in the future.
I'd agree with you, does sound like an alternator fault. On mine the exhaust is lagged and the alternator also has reflective heat shield round it. Seems to be OK, touch wood.
GreenV8S said:
On mine the exhaust is lagged and the alternator also has reflective heat shield round it. Seems to be OK, touch wood.
What did you use to lag the exhaust ?
I had the alternator tested today and there is a fault on it so a recon’ higher current unit is coming in the next couple of days – fingers cross this will sort it out.
Hope I’m not speaking too soon here but I’ve put the new alternator on tonight. I took the car up the road to put some petrol in it and gave it a 20min blast back home. So far touch wood no voltage problems and the hesitation has gone along with the petrol I put in 
Thanks for all your advice
Thanks for all your advice
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