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LEGACY VENDOR
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1,108 Posts
Discussion Starter #1
Hey guys. I have decided a few months ago to use the old 96 P38 everyday. Slowly I have been replacing lots of parts. I have the following electrical problems and measurements. I see several trouble spots in the measurements but am unsure what the underlying cause is maybe you have some ideas. I am thinking that the new battery was damaged by the weak alternator that I just replaced. And the problems now are because the battery is weak? But shouldn't the brand new alternator be able to produce the correct voltage at the alternator.

Everything appears to be way off. The vehicle has a 4 month old AGM battery (925CCA 1100CA). Just replaced original alternator with BOSCH. Cables do not show any obvious signs of corrosion. Symptoms are a weak battery, Alternator fault on dash, incorrect fuel gauge.

12.33v 1. Engine off, all accessories on for 30 seconds, then off. What voltage
13.30v 2. Voltage across battery at idle (no electrical load)
13.40v 3. Voltage across battery at 2000rpm (no electrical load)
13.30v 4. Voltage across battery at 2000rpm (everything electrical switched on)
14.05v 5. Voltage at ALTERNATOR at 2000rpm (everything switched on)
50Mv 6. Voltage drop between alternator body and battery negative (YES negative). Measure at max electrical load and 2000rpm
215Mv 7. Voltage drop between alternator positive and battery positive. 2000rpm, max electrical load
3Mv 8. Check Voltage drop from Battery Negative terminal to 1st groundpoint on vehicle
46Mv 9. Check voltage drop from 1st ground point to block
1Mv 10. Check voltage drop from Alternator Housing to block
14.06v 11. Voltage from alternator positive to alternator housing
 

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1995-2002 Range Rover P38A
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3,952 Posts
Re: Electrical Sticky Submission - Stumped from all directions

Number 7 is the clue. You are losing 0.2V between the alternator and the battery. The cable from the battery runs to the starter motor and another cable from there to the alternator. A bit of dirt and corrosion on the two cables will cause all sorts of problems. Take them off and clean them.
 

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LEGACY VENDOR
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1,108 Posts
Discussion Starter #3
Re: Electrical Sticky Submission - Stumped from all directions

Excellent advice, thank you. I will take that direction immediately. Oh wait...:shock:
0221151603a.jpg
Maybe it will have to wait a bit. I will get to it when there is not snow flying everywhere.
 

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Premium Member
1995-2002 Range Rover P38A
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249 Posts
Re: Electrical Sticky Submission - Stumped from all directions

I concur with what Gilbert said. Try cleaning up the positive connection between the alternator and the battery. The voltage at the battery is low while charging which is probably because of the voltage drop you observed. Cleaning up should make a world of difference in your case. Don't forget to report back with your findings :thumb:
 

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JACK'S GRANDAD
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9,242 Posts
Re: Electrical Sticky Submission - Stumped from all directions

I run a direct feed to the battery from the alternator in most cases. Yeah yeah yeah, it shouldn't be required and wasnt like that from the factory etc, but these rigs ARE nigh on 20yrs old now, so I personally doubt they are as good as new anymore.
Try running a lead from the alternator to the battery, then a starter lead from the battery instead. I have found this to be a much better way myself, as did pretty much every auto manufacturer apparently......

Marti
 

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LEGACY VENDOR
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1,108 Posts
Discussion Starter #6
Re: Electrical Sticky Submission - Stumped from all directions

I cleaned up the connections on the positive terminal gave everything a good wiggle test and tightened everything down. I got the following changed towards the better. Still much more to do with the starter motor area of the problem. The weather makes it difficult.

120Mv 7. Voltage drop between alternator positive and battery positive. 2000rpm, max electrical load

One other symptom, the alternator is extremely hot to the touch while the engine is still cold. The alternator is also producing a very unpleasant "new" hot electronics smell. Not sure if this is break in period stuff or if the alternator is under too much load from something.

Get out of the way Toyota, the Rover needs the space.

0221151724.jpg

 

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1995-2002 Range Rover P38A
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3,952 Posts
Re: Electrical Sticky Submission - Stumped from all directions

That's an improvement but still not there. I put serrated washers on between the two cables on the starter on mine and got it down to less than 10mV. Alternator shouldn't get hot or smell so there's something not right there.
 

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Re: Electrical Sticky Submission - Stumped from all directions

Yes, alternator/charging problem for sure, you should see 13.8-14.4V across the battery (at any revs. ). If the battery was seriously 'strained' due to previous problems then it could now have a weak cell. This makes the alternator have to work harder (ie. supply a higher current and so probably reduced volts too); Swap the battery out and/or have it 'load' tested. Alternatively (and maybe when the snow melts...) try an 'intelligent' charger on the battery and this might show up the problem, too (?); With an intelligent charger a weak cell generally means you can only charge it to maybe 60% or so capacity.....
 

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LEGACY VENDOR
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Discussion Starter #9
Re: Electrical Sticky Submission - Stumped from all directions

Yeah I am concerned about the alternator smell and temperature. Either it is under too much load or perhaps it is possible the "new" alternator is damaged. Does anyone know what the normal range of current draw should be on an idling engine?

I too think that the battery may be toast. The battery is an AGM Exide XRF-31E. Supposed to be extremely tolerant of discharge events. And given that the battery is only 4 months old with probably less than 2000 miles on it, I would be surprised if the battery has kicked it. I put the battery on an 8 stage charger last night.
 

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Premium Member
1995-2002 Range Rover P38A
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249 Posts
Re: Electrical Sticky Submission - Stumped from all directions

You could always put a clamp meter around the cable to see what kind of current it's pushing. Might give you an idea if it's not pushing very much current and still getting hot that you may have an alternator that's going out.
 

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Re: Electrical Sticky Submission - Stumped from all directions

Hi Storey, I didn't realise it was you. Was just playing with your EAS software this morning! (I fitted a yellow relay to replace the delay timer and tested if your software still works. It partly does).

#1

At 12.33 volts your battery is quite discharged. If it were full, within 60 seconds of loading your battery as per test 1, your battery would be back up to reading 12.6 or even 12.7 volts after this test

How does it test up (according to the 30 second load test procedure) immediately after charging?

In cold weather, which I assume applies from your location, it will take a higher voltage to charge your battery. To charge the battery to 100% in a day or less will need 14.4 volts. 13.3 volts charging voltage in cold weather is battery abuse. But I bet you haven't killed it yet.

#2 Too low. Later tests explain why

#3 As per #2

#4 As per #2.

#5 Your alternator is producing good voltage under load. It is maintaining performance of both voltage and load.

#6 That a good result if true but it doesn't make sense. According to test 4 and 5, under the specified test conditions, your alternator is producing 14.05 volts but only 13.3 volts is getting to the battery. This means 0.75 volts (750mv) is being lost between your alternator and your battery. In test 6 you say you are losing 50mv in the negative and in test 7 you say 215mv is being lost in the positive. This is 265mv. However, you haven't accounted for almost 500mv of loss. This loss has to be in either or both of the positive or negative circuits between the alternator or battery.

#7 I suspect is wrong for the reasons above. However it is a bad result in its own right and you need to spend $15 on a new, extra positive wire from a battery shop. Fit it between the alternator positive and the battery positive. From memory I used a 4 gauge - don't use anything thinner. 2 gauge is better (fatter), if it fits. Clean up and refit the existing wires too. Fit this one as an extra. While you are at it, do the same for the negative. Total cost $20 or $30.

Tests 8,9 and 10 should also be done at max electrical load (high beams, blowers, demisters etc) and 2000rpm.

Can you rerun the tests and let us know the numbers?

Also regarding the smell and heat and alternator fault. Seems unusual. I wonder if the car has a short somewhere. Can you get a DC clamp meter to read the current draw from the alternator and how much is going to the battery (with the car running at 2000rpm and all electrical loads switched off)?

Alternator fault messages are not normally the symptom. Normally the car will flash up lights like a police car, windows won't work and indicators wont work. I wouldn't expect an alternator fault message. Combined with the heat and smell it makes me wonder? What about the small sensor wire from the alternator. Is that in good condition?

Thanks again for your awesome EAS software!

Greg
 

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LEGACY VENDOR
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Discussion Starter #12
Re: Electrical Sticky Submission - Stumped from all directions

Thanks Greg, I greatly appreciate your attention on this matter. I am not finding an easy answer to this. Here is where I am going to go from here.

I am going to use a different multi-meter (just in case).

The battery after a fresh charge on an 8 stage charger drops to 12.33 after 30 seconds of headlights. So I would imagine the battery is indeed toast. I am getting a replacement under warranty.

I got the Positive lead Mv drop down to 140Mv after cleaning. So I will follow your advice and get new cables.

I will do the battery and the cables, then see if I can get my hands on a clamp ammeter.
 

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1995-2002 Range Rover P38A
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Re: Electrical Sticky Submission - Stumped from all directions

Hi Storey,

Sorry I can't add anything to the last post, but it is nice to see you!

Cheers.
 

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208 Posts
Re: Electrical Sticky Submission - Stumped from all directions

I am going to use a different multi-meter (just in case).

The battery after a fresh charge on an 8 stage charger drops to 12.33 after 30 seconds of headlights. So I would imagine the battery is indeed toast. I am getting a replacement under warranty.

I will do the battery and the cables, then see if I can get my hands on a clamp ammeter.

Doubt it is the multimeter but it does not hurt to 'eliminate other variables' ! P38s really needed a permanent voltmeter in the dash; Even just one in the cigar lighter socket can help.

When you used your 8-stage charger what '% charge' did it show when finished charging ? If over 90% this tends to point away from the battery, but you can only tell for sure under high/er loads. Might be a good idea to charge it back up again and have it properly 'load tested' when you return it for replacement (?). That is a Heavy Duty battery and as such it has high current demands, too ! You may thus find that the combination of heavy duty battery and a (marginal) 'new but not HD' alternator is the main issue here.

A clamp meter reading may be useful but only if you have something to compare it to.

Bit late to ask but what was wrong with the original alternator ?

EDIT: Can't find it but there is a post on here somewhere about using '150A' replacements for '120A' alternators.

Found one:

http://www.rangerovers.net/forum/7-range-rover-mark-ii-p38/32391-alternator-voltage-120-vs-150-amp.html

Spec for the battery gives its weight as 78 pounds..... !
 

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A clamp meter will tell you how much current is going into the battery and where else it is going. They cost less than 50 bucks and a bloke like Storey should have one. Make sure to get a dc capable clamp meter (read the spec sheet not the eBay title). eBay or radio shack or Amazon???
 

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Storey when you do test #1 do you turn the lights back off and wait 30 seconds before taking the voltage reading? If not, charge the battery all the way again and do it that way

Also wee all the other tests done at 2000rpm and with lights on high, blower fans on max and rear demister on?
 

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LEGACY VENDOR
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Discussion Starter #17
Re: Electrical Sticky Submission - Stumped from all directions

In answer to a few questions.


The battery test was done as according to the following. Charge with 8 stage charger. Measure voltage, 13.7v. Perform 30 seconds with load headlights only and no engine. Wait 30 seconds. Measure (12.3v). I think it safe to safe, the battery is Kaput.


Why did I install a new alternator? Well the the battery is so amazingly awesome and new, I thought it could not possibly be the battery. So when I saw a weak battery and low output from the alternator, I jumped to conclusions and went with new alternator. Opps.


Interesting observation. All positive cable connections were cleaned and star washers installed. The voltage between the Alternator positive and Battery positive while the engine is running is inversely related to the battery voltage. In my situation. I wonder if this battery is so damaged that it is causing all the other symptoms.


Batt 14.75v Engine running at 2000 RPM, charger on Supply mode, fixed voltage varying current, the voltage drop is only about 30 mV.
Batt 12.4v Engine running at 2000 RPM, no charger, the voltage drop rises to about 120 mV.
Batt 12.20 Engine running at 2000 RPM, no charger, the voltage drop rises to 250 mV


The new battery arrives on Monday March 2nd. I will update then. Cross fingers all the gremlins go away.
 

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Re: Electrical Sticky Submission - Stumped from all directions

Hope you are right about the battery Storey but don't dismiss the combination of using a standard alternator with a heavy duty battery just yet..... One of the characteristics with such 'deep discharge' batteries is that they can be re-charged rapidly - but this takes more current to achieve.

One other way - although admittedly a bit vague- to check all this is to use an IR thermometer on the alternator with the 'old' battery and then the new one.... although hopefully there should be less 'burning smell' etc with the new battery, too !

Incidentally has anyone used a clamp meter on their rigs and if so what results did you get ?
 

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1995-2002 Range Rover P38A
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Re: Electrical Sticky Submission - Stumped from all directions

Charge with 8 stage charger. Measure voltage, 13.7v. Perform 30 seconds with load headlights only and no engine. Wait 30 seconds. Measure (12.3v). I think it safe to say, the battery is Kaput.
I'd agree totally, one cell has gone down. I've had it happen on two cars that have been left standing. Battery perfectly OK, leave them for a while so the battery goes flat and when I've come to charge them they seem to take a charge and work but if left for more than a couple of days can't deliver the goods. Immediately after charging the voltage seemed fine but as soon as a load was put on them, it dropped quite a bit. Both were the older style with caps on each cell so I was able to use a hydrometer and found that on both, one cell was doing nothing.
 

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Storey, voltage drop will and should be inversely proportional to battery voltage. As the battery voltage drops, charge current will increase. The cable is then being forced to do more work and will therefore induce more voltage drop. Just like a current shunt really.

P38baffled I don't agree that a heavy duty battery should cause this problem. If it is fully charged to begin with like Storey did, it will not take any more charge and will not cause a load.

A large battery with a very fast charge rate which is FLAT might do it. Deep cycle batteries are typically slower to charge and discharge. I could easily see a flat lipo4 battery giving an alternator a work out.

Anyway I use oversized starting (not deep cycle) batteries and have never had a problem from that.

A dead cell should pull the battery well below 12.3 volts.

Still it sounds like a battery with an internal short of some kind or some other problem. Bosch alternator should be good and this is the second alternator with a problem

Storey don't forte to fix the positive cable - 250mv drop is well outside spec and will cause charging problems and quickly kill a battery especially in cold weather. Fix the negative too. Those two things and a new battery and you _should_ never have a problem again.

My expensive big batteries used to last me only a year. Now they last forever (7 years?). I will have had my p38 for 14 years in August!
 
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