Forums » Ask a Question

Use this forum to post your questions to our experts – you need to be logged on to do it (you can register here ), then scroll down to the bottom of this page and click the blue Post Thread words

If you can help answer the question, feel free to post a reply – you need to be logged on to do it (you can register here ), then hit the reply button on the thread.

 

To go back to the experts page click here>>

AuthorMessage
deadfish
deadfish

Posted: Sat Apr 16, 2011 4:49pm

Post Subject: Change dynamo for alternator

Hi, please could you tell me how to change from a dynamo to an alternator on a bmc 1.5 diesel, what alterations will I need to do to the wiring. Also I've just bled my fuel system, I couldn't undo the bleed scew on the side of the injection pump so as the manual described I loosened the screw on the top of the turret where the levers are. Unfortunately the nuts below it also turned before it came loose, have I disturbed any settings? Many thanks

Tony-B
Tony-B

Posted: Sat Apr 16, 2011 6:09pm

Post Subject: Change dynamo for alternator

First the bleeding. It is probable that your injector pump is fitted with an idle stabilisation valve (not all are) and this is what you have disturbed. However if it does not stall as it drops to idle ans as long as the idle speed is still acceptable then I am sure you can forget about it. But get an 8mm socket so you can undo the side bleed screw in the future. Go into the alternator section of my electrical course notes on (tb-training.co.uk) and download the alternator wiring diagram and notes. From memory the rear dynamo mounting bracket on a 1.5 is too far back for an alternator so the easiest thing to do is to get a longer bolt an a distance piece to make up the difference. You need the smallest diameter alternator pulley you can get that ALSO matches the profile of the existing dynamo belt. You can probably use the existing slotted adjusting bracket but I would see if I could get a longer alternator one. You may have to file the existing one to less width. Fit the alternator and using a straight edge check the engine pulley or pulleys are in line. If not pack the mountings with distance pieces or washers or file the brackets as required (usually the worst is just to add packings but even that may not be required. Now the wiring. Run a heavy gauge cable to suit the alternator output (see those note) from the alternator's main output terminal to the SWITCHED side of the battery master switch. If the alternator has a main negative terminal run a similar sized cable from that to one of the mounting bolts. Run a thin cable from the aux. terminal on the ignition switch to one of the dynamo warning lamp connector. Connect the other lamp terminal the warning lamp connector on the alternator. There is a terminal designation chart in the notes. Tony Brooks

deadfish
deadfish

Posted: Mon Apr 18, 2011 8:15am

Post Subject: Change dynamo for alternator

Thanks for your swift reply, I think I understand the wiring but what do I do with the existing regulator (I think thats what it is, a black bakerlite box held on with a wire clip with several cables connected to it at the bottom) thanks again

Tony-B
Tony-B

Posted: Mon Apr 18, 2011 8:48am

Post Subject: Change dynamo for alternator

Unless you can supply me with a wiring diagram for your particular boat and identify which regulator you have the only answer I can give is to leave it well alone. The A & A1 or the two B terminals, depending upon your particular regulator may be being used as a junction box so for someone who needs to ask it is safer to leave it in place with all the wires on it. If I or another knowledgeable person did the conversion we would modify the wiring if required and then cut and tape the surplus wires and remove the control box. Tony Brooks

deadfish
deadfish

Posted: Wed Apr 20, 2011 10:02am

Post Subject: Change dynamo for alternator

Thanks again for the info. will try and trace the wires to see if I can remove them. I have a choice from my local alternator specialist of either a 65 amp alternator or the same but with an earth return cable which he recommends because of galvanic action but is also £50 dearer. Which would be your recommendation. Thank you

Tony-B
Tony-B

Posted: Wed Apr 20, 2011 11:58am

Post Subject: Change dynamo for alternator

There is every chance that if you test between that negative terminal and the case that you will find them both connected. Your battery should have a main negative connected to the starter or engine block because the instruments & any glowplugs all use the block for the negative connection. I would save £50 and join many hundreds of other boats with earth return alternators. Tony Brooks

deadfish
deadfish

Posted: Wed Apr 20, 2011 1:48pm

Post Subject: Change dynamo for alternator

Thanks again, saved me £50! Have noticed that the oil pressure is high, it's showing 60lb psi both with throttle open and on idle, where manual says 50lb psi and 15lb psi idle. Engine hasn't been run for about 15 years but I've changed the oil and filter, it's a bmc 1.5 diesel. Any suggestions. Thank you

Tony-B
Tony-B

Posted: Thu Apr 21, 2011 8:32am

Post Subject: Change dynamo for alternator

It would have been better if you had started a new question so other readers knew this is now about oil pressure and not dynamos to alternators. You give no history associated with the boat or what you have done to the lubrications system so my answer can only be an ill informed guess. 1. Change the oil and filter. 2. the most likely, check the pressure with a mechanical gauge because I suspect you have an electrical gauge and the sender, gauge or wiring is faulty or has been changed for one that is mismatched to the gauge. Which is more likely depends upon the history of the engine. Tony Brooks

deadfish
deadfish

Posted: Fri Apr 22, 2011 7:28am

Post Subject: Change dynamo for alternator

With regard to running the main output cable from the alternator to the battery master switch, I don't have one. Is a battery isolator switch a requirement on a boat, in which case I'll fit one. Could I also utilise the existing amp meter by running output cable through it. Also where I purchased the alternator he advised putting an in line fuse on the main output cable, would you also recommend I do this, and if so what size fuse for a 70 amp alternator. Thank you

Tony-B
Tony-B

Posted: Fri Apr 22, 2011 12:06pm

Post Subject: Change dynamo for alternator

I am sorry but I think you really should get this done professionally. If you can send me an accurate wiring diagram for your boat I will try to help but at present the questions make me suspect that you are not competent to do the job without on site help. The Boat Safety Scheme requires the vast majority of boats on UK inland water to comply with its regulations and battery master switches are one of them. You may have a switch in the negative battery line but this is not best practise. You may have a big rotary switch marked Bat1 Bat 2, Both & Off but this complicates things further unless I can see a wiring diagram. If this is a UK inland boat without a master switch it should prove impossible to license it because it can not obtain a boat safety certificate. You are then in the position that the boat may be subject to a court order and taken from you. So much here depends upon unknowns. If you disconnect the alternator from its load (the battery) whilst it is charging (like when a fuse fails as it inevitably will) you are very likely to destroy the alternator. Fusing the main lead is questionable because you are playing the odds of a fuse failing and destroying the alternator or the main lead shorting out and catching fire. The latter should not happen if you inspect and service the boat diligently. The former eventually will. If I had thought a fuse in the main lead to be a good idea I would have told you in my first reply. Perhaps you should now direct your questions on this topic to the alternator vendor. Tony Brooks

Most Read

Newsletter Sign Up

Canal Boat monthly newsletter
Sign up to receive our regular email newsletter

Our Privacy Policy

Like us on Facebook



Follow us on Twitter

Cache: Disabled for this object  Total Queries: 43.  Total Objects: 162.  Total Unserialized: 3. Total Runtime: 0.62 seconds.