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1995-2002 Range Rover P38A
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Discussion Starter #1
Any ideas would be great. Logic seems to suggest battery is the issue but....


1. Engine off, all accessories on for 30 seconds, then off. What voltage ___12.3___
2. Voltage across battery at idle (no electrical load) ____13.4________
3. Voltage across battery at 2000rpm (no electrical load) ____13.8____
4. Voltage across battery at 2000rpm (everything electrical switched on) __12.94_______
5. Voltage at ALTERNATOR at 2000rpm (everything switched on)__________14.3_________
6. Voltage drop between alternator body and battery negative (YES negative). Measure at max electrical load and 2000rpm ____.8__________ (millivolts please)
7. Voltage drop between alternator positive and battery positive. 2000rpm, max electrical load ___didnt get this one. readings jumping all over the map
8. Check Voltage drop from Battery Negative terminal to 1st groundpoint on vehicle_______1.4_______
9. Check voltage drop from 1st ground point to block___aprox 30? again, readings all over the place_______
10. Check voltage drop from Alternator Housing to block___1.5_______
11. Voltage from alternator positive to alternator housing 14.2

Rover will not start. Had to jump to perform above tests. Just had oem (bosch) alt. rebuilt. tested at 150 amps.
Had battery hooked up to slow charger 1.5 days while alt. was in shop. On reinstall, fired up just fine. Took it for a 10 min. drive. fine. Parked overnight. Wouldn't start next morning. Had to jump.

Was thinking positive cable clamp could be problem since loose enough to remove from post even while fully tightened. Only problem is it's been like that for two years and never had a problem starting before so.... Alt.'s basically new so can't be that.

Thinking about just buying a new battery and see if that fixes it. If not then back to the old drawing board. Unless anyone can see an obvious problem from the readings above.

Many thanks.
michael
 

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LEGACY VENDOR
1995-2002 Range Rover P38A
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4,216 Posts
It sounds to me like your cables from the alternator to the battery are shot... most likely to be the negative ones, as they go through a couple of ground points to get to the Battery...

If you're seeing 14.2/14.3V at alternator, but only 13.4V at alternator, then the only thing between the 2 is the cables. 13.4v won't be enough to keep the battery charged.

Also, have a look on the main site about the issues with RF interference waking the BECM up and draining batteries - it could be another symptom of why your battery is going flat.

I would check the cables first, and then see how things are... my first 1995 had earth strap problems - they looked fine externally, but had started to corrode under the plastic insulation. you should be seeing well over 14V at battery to show it's charging properly.

Cheers,
Martin
 

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1995-2002 Range Rover P38A
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36 Posts
Discussion Starter #3
Thanks Martin for the suggestions. I agree that if the alt. is healthy and battery is not charging correctly then it has to be the connection. Have not checked them too thoroughly just yet. Bat. was under partial warrenty so replaced it and lo and behold she fired right up, and has the past two days since replaced. Still going to check the cables though just to prevent a repeat.

It may just be when alt. did go south the old bat. was drained beyond recovery. We'll see.

Next up the dreaded heater core. did the o-rings, which were shot, yet core itself is leaking so that's going. Happy days..... Oh and just for fun, the right blend motor just died, so that's next. At least it had the decency of dying while the entire glove box area is still disassembled.

Thanks again mate.

Cheers!
 

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Both your positive AND negative connections from alternator to battery are shot. Allowable voltage drop is 150mv (0.15 volts). Your negative is TEN times that and your positive is almost as bad. The sticky explains it in detail.
 

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1995-2002 Range Rover P38A
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36 Posts
Discussion Starter #5
Thanks Greg. Put a new battery in, warrenty, worked just fine then of course now it wont start. Had local shop quote price of $250 for pos. cable assembly. Any suggestions on building this myself? Not an electrical engineer by trade.
 
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