Excessive Voltage??

[Tony]

Can anyone explain why an an alternator charges at 14 / 14.2 volts on the test bench, and then soars to 15.3 / 15.4 volts when back in the vehicle??? I just had my alternator's regulator and rectifier replaced because of bad fluctuations in voltage with spikes of up to 16.5 volts and drops down to 12.8 v and so on continuously whilst driving. The alternator now seems to be charging more constantly, but is sitting at 15.4 volts - and only drops a little with all lights and spots switched on. I am leaving on Saturday on a 4000 odd km trip around the Cape and am a little concerned that something is going to go wrong. I have an auto electrician that is going to try and look into it tomorrow but I'm not sure that he has enough time to fiddle and get to the bottom of the problem. My madman was installed about a month back, and has picked up this problem so i'm not sure how long it may have been like this. Any ideas or pointers to try pinpoint the fault will be appreciated. Cheers.

[Peter Connan]

Tony, to my knowledge there is nothin on the car that can push the voltage up. As far as I can figure, there are two possibilities here:

1) The test bench revs too slowly (an alternator will deliver lower volts at very low speeds).
2) One of the two voltmeters are incorrect. Use the same voltmeter to see if that makes any difference?

Good luck

[Tony]

Thanks Pete - i've got Driko racking his brains as well !!

[ChristoSlang]

1. It may well be the Madman that's not telling you the truth! Use a multimeter to double-check the Madman, and pay heed to the following from the Madman's installation manual:

"Further to this it is very important that the engine block has a good electrical connection to the negative supply terminal of the EMS-1. Any voltage drop caused by other equipment on the ground wire will cause incorrect readings. The best way to ensure a good connection is to wire a single connection between the EMS-1 ground wire to the engine block. Don’t wire this anywhere else and do not allow any other equipment to use this wire as a current return path."

2. Also make sure that your battery cables make proper contact. Check the other side of the earth cable (where it goes to the body-work), and also check the earth connection between the body and the motor. With age these corrode/oxidise/etc and the resultant bad contact cause all manner of spikes and things to occur. My Sani died on me at De Wildt many years ago due to an earth strap that did not make proper contact (but looked fine from the outside)...

[Tony]

Thanks Christo, we'll check all earth wires - although the sudden spikes seem to be gone now that the regulator and rectifier have been replaced, it's just the >15 volts that worry me.

[Tinus lotz]

Tony put aa mutimeter on the battery and switch the lights on and off airrcon ect and see what happends???

[Tony]

What am I looking for Tinus - I have already tried with all lights & spots on, and the madman drops to around 14.8. I havent confirmed this with a multimeter directly onto the battery though. I'll do it this morning.

[Tony]

Hi guys - i'm back from a very eventful 2 week trip including Prince Alfred, Knysna, Baviaans, Prince Albert, Swartberg, Die Hel, Karoo Nat. Park and finally Kimberly. Absolutely awe inspiring mountains and great roads not to mention the superb means of travel - my Patrol!!

Only one problem..... remember my last post about excessive voltage the week before the Easter weekend, well the auto electrician that repaired my alternator was too busy to try and sort this out on the Wednesday so he told me he would look into the problem on the Thursday (Now I was leaving on Saturday). Thursday came, and I could'nt get hold of him until around lunch time on his cell, only to be told that he decided to take the day off because he had such a bad day on Wed, but that I should'nt worry too much as lots of Japanese alternators do charge higher than other makes - and to call him if I had any issues!!

So off we went early Saturday, all went well, until about 50km outside Bloem I noticed my madman showing the voltage down from 15.3v to 12.4v. For a minute I thought somehow the problem had resolved itself.. and then my wife asked me to pull over to take photo's of the serious storm that was about to hit us, and I see the alternator light coming on, we moved on and it went out - does this mean that it's still charging even just a little??? My mind was now working overtime, and the knot in my stomach was tightening, and I now had lights and wipers on and voltage was down to 12v. Ok ask Garmin to find nearest Nissan dealer which was Bloem, cool we just made it there by 11H45 Sat morning.....doors locked and the same for every workshop. After driving around we found a sign with an after hours number and eventually we had a techie looking at the car by 13H30 only to find that the alternator was expired, and nothing could be sourced before Tuesday morning! (I had already prepaid all my accomodation for the entire trip starting with Sat night in Colesburg, then Sun and Mon nights in Baviaans Kloof before heading into Knysna)

Anyhow, to cut a long story short, we started working on the car by 09H00 on Tuesday and found a replacement for R2500.00 - and by 13H30 we were on the road, only to find the alternator light flickering on randomly. So it was back again and another alternator was installed - same problem - after lots of head scratching, at around 17H00 another alternator was collected and put in, needless to say, the poblem persisted and it was a while later that a positive lead was brought to the alternator from the wiper motor as it seemed that there was a loose contact coming from the ignition somewhere and it was around a quarter past seven that night that we eventually left the workshop - and ended up sleeping over in Bloem one more night before leaving on Wed morning.

We shot directly to Knysna via Prince Alfred Pass and managed to still do everything, even Baviaans, which we had to drive through in a day which was too short, but at least we went.

Only, I now have picked up the madman's coolant temp. reading being affected by all electrics - it started with the lights, turn them on and the coolant temp suddenly climbs between 5 and 8 degrees - turn on the spots and its 12 to 15 degrees and the warning lights and beeps start - the same applies to the indicators, fan/aircon, radio, wipers, windscreen washer, hooter etc..

Apart from that, the car went superbly and the trip was really awesome!

[Tinus lotz]

Tony glad to hear that ur trip was lekke is sounds like ur main line rely or something else is giving u problems ......take it to Mr Cumming he is in vallala he will sort it propery. For u he is a auto elec fist and a patrol professor if you need his no give me a call !!

[Tony]

Dankie Tinus, do you not think it could be a madman issue - I spoke to the guys at SAC and they have had similar faults in the past with temp readings as well as erratic boost readings. Mind you, I have also been picking up strange boost signals and was thinking in the line of replacing the boost sensor. Only problem is that I am now not too sure if this madman is giving me correct readings - maybe there is something not right with my electrics??
Please send me his contact number - maybe I should have a chat with him.
Cheers.