Doc76016 Posted August 8, 2012 Share Posted August 8, 2012 My FV-721 is not charging the batteries. I have heard that a common problem is "dirty contacts" on the bucking regulator in the distribution box. I have removed the distribution box from the vehicle. Before I open it up does anyone have any tips? Thanks, mdh Quote Link to comment Share on other sites More sharing options...
FourFox Posted August 8, 2012 Share Posted August 8, 2012 I did mine yesterday. It' probably the main contactor that has white fur on the copper contacts. You will hear the large relay go 'clunk' as the revs rise...but still no light. A quick scrape with 400 grit emery sorted the problem in a few minutes. I check the contact resistance to make sure that there is no debris still on the contacts. It should read close to zero ohms when you push the contacts together. It is also quite common for there to be a fault in the ammeter shunt circuit...just check the battery volts whilst running to see if it is really not charging. It's best not to mess with the regulator relay unless you are good at re-setting the cut-in voltage. It is just about impossible to clean the contacts without disturbing the relay spring. The tension on this spring determines the voltage that the alternator connects to the battery. Get it too low and the battery drains through the alternator. Get it too high and it will seriously overcharge. Don't forget that these alternators are rated at 200 amps! It is also capable of outputting voltages in excess of 200v dc if you get it really wrong. Incidently I worked out that the fan drive coupling on a Fox has to absorb 50hp when charging at full whack! I have reset a Fox regulator using a variable voltage power supply and lots of dummy resistors (variacs) simulating the alternator windings. It should cut-in at about 28v. Good luck. Jon Quote Link to comment Share on other sites More sharing options...
Doc76016 Posted August 10, 2012 Author Share Posted August 10, 2012 I did mine yesterday. It' probably the main contactor that has white fur on the copper contacts. You will hear the large relay go 'clunk' as the revs rise...but still no light. A quick scrape with 400 grit emery sorted the problem in a few minutes. I check the contact resistance to make sure that there is no debris still on the contacts. It should read close to zero ohms when you push the contacts together. It is also quite common for there to be a fault in the ammeter shunt circuit...just check the battery volts whilst running to see if it is really not charging. It's best not to mess with the regulator relay unless you are good at re-setting the cut-in voltage. It is just about impossible to clean the contacts without disturbing the relay spring. The tension on this spring determines the voltage that the alternator connects to the battery. Get it too low and the battery drains through the alternator. Get it too high and it will seriously overcharge. Don't forget that these alternators are rated at 200 amps! It is also capable of outputting voltages in excess of 200v dc if you get it really wrong. Incidently I worked out that the fan drive coupling on a Fox has to absorb 50hp when charging at full whack! I have reset a Fox regulator using a variable voltage power supply and lots of dummy resistors (variacs) simulating the alternator windings. It should cut-in at about 28v. Good luck. Jon Thank you for your helpful and informative reply. I'll check it out this weekend. mdh Quote Link to comment Share on other sites More sharing options...
Doc76016 Posted August 14, 2012 Author Share Posted August 14, 2012 Well, I pulled the distribution box and opened it up. There seemed to be only a slight bit of corrosion on the contacts of the big relay. I gingerly cleaned that up. There were several smaller relays. They seemed to be fairly clean so I left them alone. I then replaced the box but nothing has changed. The alternator light is still on and the ammeter does not move. A VOM shows no charge delivered to the batteries. With the engine running I applied a battery charger to the batteries but the light did not go out or dim and the ammeter did not move at all. Does this give you a clue as to what might be the problem? I'm going to remove the box again this weekend and see if the main relay will operate if i apply voltage directly to it. Thanks, mdh Quote Link to comment Share on other sites More sharing options...
Richard Farrant Posted August 14, 2012 Share Posted August 14, 2012 My FV-721 is not charging the batteries. I have heard that a common problem is "dirty contacts" on the bucking regulator in the distribution box. I have removed the distribution box from the vehicle. Before I open it up does anyone have any tips? Thanks, mdh It might seem a stupid question, but have you checked to see if the alternator drive belt is still intact? Quote Link to comment Share on other sites More sharing options...
Marmite!! Posted August 15, 2012 Share Posted August 15, 2012 We had a problem a few years back where the wire to one of the pins in the Alternator socket was broken.. Quote Link to comment Share on other sites More sharing options...
Marmite!! Posted August 15, 2012 Share Posted August 15, 2012 This should answer all your questions.. http://hmvf.co.uk/pdf/FoxChargingSystem.pdf Quote Link to comment Share on other sites More sharing options...
Doc76016 Posted August 16, 2012 Author Share Posted August 16, 2012 This should answer all your questions.. http://hmvf.co.uk/pdf/FoxChargingSystem.pdf Wow! Fantastic resource! I have downloaded it and will study it carefully. A million thanks. mdh Quote Link to comment Share on other sites More sharing options...
Doc76016 Posted August 16, 2012 Author Share Posted August 16, 2012 It might seem a stupid question, but have you checked to see if the alternator drive belt is still intact? Not a stupid question at all. Unfortunately, the belt is intact so it's not that simple. mdh Quote Link to comment Share on other sites More sharing options...
Doc76016 Posted August 16, 2012 Author Share Posted August 16, 2012 We had a problem a few years back where the wire to one of the pins in the Alternator socket was broken.. I did find a few connections that were partially broken and resoldered them but that wasn't it. mdh Quote Link to comment Share on other sites More sharing options...
Doc76016 Posted September 9, 2012 Author Share Posted September 9, 2012 Well, I finally got a few moments to do some more troubleshooting. I decided to see if the alternator is actually providing voltage to the distribution box. After studying the system I decided to disconnect the large cable at the distribution box. I then fitted appropriate wires to the pins and inserted them into the sockets being careful to maintain the correct routing and leaving the pins exposed so that I could attach a voltmeter. I assumed that the main charge would be from the two very large pins. With the engine running at approximately 1500-1800 rpm I measured only 4.2v. I also measured every possible combination of plugs and ground. I got 4.2v at a couple of places and 3.1v at another couple and nothing at the remainder. Does this indicate a bad alternator or cable from the alternator or is my major premise of 28v at the large pins wrong? Thank you, mdh Quote Link to comment Share on other sites More sharing options...
Marmite!! Posted September 9, 2012 Share Posted September 9, 2012 Well, I finally got a few moments to do some more troubleshooting. I decided to see if the alternator is actually providing voltage to the distribution box. After studying the system I decided to disconnect the large cable at the distribution box. I then fitted appropriate wires to the pins and inserted them into the sockets being careful to maintain the correct routing and leaving the pins exposed so that I could attach a voltmeter. I assumed that the main charge would be from the two very large pins. With the engine running at approximately 1500-1800 rpm I measured only 4.2v. I also measured every possible combination of plugs and ground. I got 4.2v at a couple of places and 3.1v at another couple and nothing at the remainder. Does this indicate a bad alternator or cable from the alternator or is my major premise of 28v at the large pins wrong? Thank you, mdh I thought the testing procedure was fully covered in the pdf I put in my previous post? Quote Link to comment Share on other sites More sharing options...
fv1609 Posted September 9, 2012 Share Posted September 9, 2012 I assumed that the main charge would be from the two very large pins. If you mean pins 3 & 4 they only provide the +ve output, the -ve is via earth. Pin 3 is to supply +ve output to hull batteries Pin 4 is to supply +ve output to turret batteries Pin 3 & 4 are only joined together & to the alternator output once the main relay RL2 is activated by the driver relay RL1 energised via the auxiliary alternator output feeding pin A. Your best place to monitor +ve alternator output is pin B or C that feed the ammeter & of course -ve from the earth. (I assume we are talking about Gen Panel No.12 Mk 1) Quote Link to comment Share on other sites More sharing options...
Marmite!! Posted September 9, 2012 Share Posted September 9, 2012 (I assume we are talking about Gen Panel No.12 Mk 1) No.12 Mk1 is the generator... the Control & Distribution box is No.1 Mk2 See page 2 http://hmvf.co.uk/pdf/FoxChargingSystem.pdf Quote Link to comment Share on other sites More sharing options...
fv1609 Posted September 9, 2012 Share Posted September 9, 2012 Yes you are right. Unfortunately my circuit diagram labels it incorrectly. My other mistake was to assume CVR(W) & CVR(T) had the same charging arrangement. Although they are broadly similar I didn't realise the CVR(W) used the a vibrating contact regulator which is rather crude unlike CVR(T) with CAV 440 module at the heart of the panel. Quote Link to comment Share on other sites More sharing options...
Doc76016 Posted September 9, 2012 Author Share Posted September 9, 2012 I thought the testing procedure was fully covered in the pdf I put in my previous post? Indeed. However, as I lack the proper test cable or access to such, I am forced to improvise. Your PDF file is extremely helpful and very much appreciated. Reading through it again I see that I stopped one step short. I have now completed the testing on page 25. I get 4.2v as described in step 4. However, at step 6 I detect no voltage. I still need to test the cable before concluding that the alternator is defective. Thank you, mdh Quote Link to comment Share on other sites More sharing options...
Doc76016 Posted September 9, 2012 Author Share Posted September 9, 2012 Yes you are right. Unfortunately my circuit diagram labels it incorrectly. My other mistake was to assume CVR(W) & CVR(T) had the same charging arrangement. Although they are broadly similar I didn't realise the CVR(W) used the a vibrating contact regulator which is rather crude unlike CVR(T) with CAV 440 module at the heart of the panel. Are the two regulator types interchangeable? Quote Link to comment Share on other sites More sharing options...
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