New Alternator Getting Hot....

Discussion in 'Tech/Mech General' started by paulmj, Jul 28, 2008.

  1. paulmj

    paulmj Deleted User

    Guys,

    There is a whole long saga revolvong around the alternator in my RV. I won't bore you with it here, but here is a synopsis of my current issue (I hope, rather than problem) taken from the RV section:

    "Well the problem seems to be solved - or the plot thickens............

    I managed to find a brand new replacement alternator on US ebay. I can't believe I didn't think of it sooner. I just looked through the pictures until I found an alternator that looked the same. Job done. I got a direct replacement, 130A job delivered to my door in 6 days for £85 including insurance! I was amazed.

    I've just fitted it and almost all seems well. When I start the engine it behaves as ait should. So the old alterantor was definitely duff and causing all of my problems. However, the new alterantor gets too hot to touch after about 60 secs of running.

    It isn't an alectrical issue as with all of the electrics on and the ignition switched on it doesn't get hot. It is only when the engine is running.

    So, is this likely to be because it is a brand new alternator and the brand new bearings are a little tight and need to wear in? Or is it just that the batteries are a touch low and it is having to work hard while brand new? I've put the genny on for a bit to top the batteries up and I'll try it again.

    A big leap forward and the electrical issues seem to be solved.

    But I'd be grateful for your thoughts on the heat issue."


    I think it is getting 'a bit less hot' each time I run it.

    I'd be grateful for your thoughts on the heat issue.................

    Many thanks in anticipation.

    Paul

    :Smile:
     
  2. pappajohn

    pappajohn Funster Life Member

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    its only doing any work when the engines running.:Doh:........:Rofl1:

    did you get some external charge in the batteries then try again. is it still getting hot.?
     
  3. paulmj

    paulmj Deleted User

    Exactly!

    It is only working with the engine running. And tonight I ran it with the field excitation swicthed off and hey presto it didn't get hot.

    Basically, it is getting hot because it is working very hard. Tomorrow night I will run it with the leisure batteries disconnected to see if it is the same. It has a new vehicle battery on but the leisure batteries are a couple of years old and have been overcharged by the duff old alternator - they have been topped up and hold a charge ok though.

    So the question is....... assuming the leisure batteries are ok (and it still gets hot with just the, brand new, vehicle battery attched) is it normal for it to run so hot when working hard and do I need to worry about it?

    I ran it for half an hour tonight and it got hot pretty quickly, but then gets no hotter. It doesn't seem to effect its operation. And yes, once the batteries are fully charged it will probably run much cooler.......

    Things are never simple..........

    :)

    Paul
     
  4. pappajohn

    pappajohn Funster Life Member

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    i assume you have a car for everyday use.........

    try starting that and turn on the lights ect and see how hot that alternator gets.

    it should give you some idea. :thumb:

    john.
     
  5. paulmj

    paulmj Deleted User

    Fair point...........
     
  6. American Dream

    American Dream Read Only Funster

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    Paul,

    Just a thought.

    Occasionally they have a habit of supplying an alternator without a cooling fan and pulley.

    Did the new one come with a fan, and did the old one have one.Sometimes they just aren't fitted, I assume they think the flow over it is sufficient.

    The reason being, I'm currently looking on an american site for another alternator.

    Steve.
     
    Last edited: Jul 29, 2008
  7. paulmj

    paulmj Deleted User

    Yeah, it is an internal fan model. I was wondering if it had been fitted the wrong way round though.

    However, I have done a bit more fiddling.

    I disconnected the leisure batteries and noted a few things:

    Firstly, they are experiencing a 300mA drain at standstill. Not a massive amount so could be down to things like the memory on the radio etc.

    Secondly, when I disconnected them the alternator didn't get hot and the engine wasn't working as hard! Or so I thought, after a moment, it got hot again. I suspect once the split charge relay came in. So I am suddenly thinking I may have a small leak to earth somewhere - possibly even internally in the split charge relay - it is a great big clunking mechanical thing.

    So tonight I am going to disconnect it in toto to ensure it isn't queering the pitch, test each circuit on the leisure side to ensure I haven't got a short somewhere and then reconnect things one by one.

    So, onwards and upwards........

    :)
     
  8. paulmj

    paulmj Deleted User

    Well, I've tested evrything tonight. There are no circuit faults anywhere and I am confident that the batteries are all good.

    It just seems to be that it is getting hot as it is working hard.

    I don't think it is getting as hot now - you can now keep your hand on it, although it feels very hot to the touch.

    I wonder if it is just running in............

    ????

    :Sad:

    If only life was simple.
     
  9. American Dream

    American Dream Read Only Funster

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    OR the work is done Paul.

    IF the batteries were nearly flat then the demand on the alternator from the word GO would have been at a possible Maximum as current was required to charge the flat batteries.

    Sounds like the situation now may have stabilised.

    You don't mention having an ammeter installed although they seem a standard fitment.

    Does this not give you any indication of the current being put out and demanded by the system?

    Hope all is ok now.:thumb:
     
  10. paulmj

    paulmj Deleted User

    Hopefully you are right!

    Sadly, I don't have an ameter installed but I keep meaning to get my hands on a DC clamp meter.

    That, I guess will be the acid test........

    :)

    Cheers.

    Paul
     
  11. fordy

    fordy Deleted User

    Hi i have fitted a new alternator on my RV and it did state on the new unit that the battery's must be fully charged, or it may damage the new unit as it will pull to much power and the alternator needs to run in .. hope this is all the prob is.

    FORDY:Smile:
     
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