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Denso alternator getting hot

gavin174 - 28/6/20 at 01:46 PM

I have read all the post I can find,
and am sure I have wired it correctly.

the engine is not running yet,
but with the ignition on the alternator is getting hot.

I have had the alternator tested and its fine.

I have connected it to a battery on the bench,
connecting the B+ to the battery and earthing the alternator everything is fine.

when I connect the switch live to the I terminal the alternator starts to heat up.

when I connect the L terminal to the negative side of a light and 12v to the other side of lamp,
spin the alternator with wheel nut gun the light goes out....

any ideas?

theconrodkid - 28/6/20 at 02:18 PM

https://www.pinterest.co.uk/pin/626422629394212127/

sounds like you have it wired right , getting hot would suggest a short

gavin174 - 28/6/20 at 02:33 PM

I have had the alternator tested,
its a brand new one I bought as a spare,

the one on the car is doing the same.

am I looking for a problem that isnt actually there,
and is caused by the alternator being "excited" but not spinning...

can someone with a Denso please put their ignition on, but not start the engine and see if the alternator heats up.

starterman - 28/6/20 at 04:10 PM

You have a short somewhere in your system. When you connect the main lead does it spark?

CosKev3 - 28/6/20 at 04:15 PM

How long are you leaving ignition on before it gets hot?

gavin174 - 28/6/20 at 04:44 PM

Probably 5 minutes..

I only have a red "missile" switch for an ignition.

So when ever the power is on,

The alternator is live..

rusty nuts - 28/6/20 at 04:56 PM

Try putting an ammeter on the switch live feed?

gavin174 - 28/6/20 at 05:02 PM

I will try to get hold of one..

But what am i looking for?

CosKev3 - 28/6/20 at 06:22 PM

quote:
Originally posted by gavin174
Probably 5 minutes..

I only have a red "missile" switch for an ignition.

So when ever the power is on,

The alternator is live..

Wonder if it would cool down when the alternator is turning so the cooling fan is doing its job?

rusty nuts - 28/6/20 at 08:25 PM

If the alternator is getting hot then there must be a fairly high amperage going through it? Starterman on here is probably the best person to ask.

gavin174 - 28/6/20 at 09:21 PM

I must be missing something really obvious...

I have had it wired up to a battery on the bench,

With just a 25mm battery cable to post B+

A 1mm cable from the battery to the IG terminal.

A 1mm cable from L via led lamp to the positive of the battery. This operates as I would expect...

I am trying to think if I had the CTEK battery maintainer switched on, could this cause the problem.

02GF74 - 28/6/20 at 09:55 PM

Lets think about what is happening here.

The alternator converts mechanical energy to electrical energy and since no system is 100% efficient, the losses result in heat.

You say the engine is not running so alternator is not producing power so is not getting hot due to that.

When ignition is turned on, current is supplied to 'self excite' the alternator, this current goes through typically a 2 watt bulb.

You can work out the current flowing.

If the bulb is in, and it should be, then all of the voltage and hence power, all 2W of, are being dissipated in the bulb do the alternator should not be getting hot.

Clearly there is a problem.

Im not familiar with the CTEK battery maintainer but remove that.

I d be surprised if that wad causing it as all it should fo us keep the battery at a slightly higher voltage and dissipate slightly more power in the bulb.

Is the body of the alternator earthed?

CosKev3 - 28/6/20 at 10:21 PM

quote:
Originally posted by 02GF74
Lets think about what is happening here.

The alternator converts mechanical energy to electrical energy and since no system is 100% efficient, the losses result in heat.

You say the engine is not running so alternator is not producing power so is not getting hot due to that.

When ignition is turned on, current is supplied to 'self excite' the alternator, this current goes through typically a 2 watt bulb.

You can work out the current flowing.

If the bulb is in, and it should be, then all of the voltage and hence power, all 2W of, are being dissipated in the bulb do the alternator should not be getting hot.

Clearly there is a problem.

Im not familiar with the CTEK battery maintainer but remove that.

I d be surprised if that wad causing it as all it should fo us keep the battery at a slightly higher voltage and dissipate slightly more power in the bulb.

Is the body of the alternator earthed?

There is another connection on these Densos,an ignition live that is connected straight to the alternator aswell as the excite wire

gavin174 - 29/6/20 at 04:42 AM

Yes the body of the alternator is earthed

I wonder if the problem is I am using an led lamp as the charge light,

I will wire in a conventional filament bulb and see if that makes a difference

02GF74 - 29/6/20 at 07:55 AM

quote:
Originally posted by CosKev3

There is another connection on these Densos, an ignition live that is connected straight to the alternator as well as the excite wire

ok, I missed that completely, then the alternator is drawing some power - how hot is it getting, warm (probably normal) or too hot to touch (cannot be normal)? And also where is it getting hot.

r1_pete - 29/6/20 at 08:51 AM

You need a resistor @50ohm 10watt in parallel with the led, and a diode In series to prevent reverse current.

If you are using a bulb on the bench and a led in the car there's your problem.

gavin174 - 29/6/20 at 09:34 AM

I am using an Led in both instances..

I think I will just add a filament bulb and hopefully that will cure the problem!!

David Jenkins - 29/6/20 at 09:39 AM

If you want to use a LED on your dash then I think that you can fit a resistor to provide the load that the alternator requires.

But do some research, as I'm not 100% sure of what value resistor, what wattage it should be, and so on!

02GF74 - 29/6/20 at 09:56 AM

quote:
Originally posted by gavin174

the engine is not running yet,
but with the ignition on the alternator is getting hot.

I have connected it to a battery on the bench,
connecting the B+ to the battery and earthing the alternator everything is fine.

when I connect the switch live to the I terminal the alternator starts to heat up.

when I connect the L terminal to the negative side of a light and 12v to the other side of lamp,
spin the alternator with wheel nut gun the light goes out....

any ideas?

It sounds like you have wired it correctly.
wiring is like this:

when alternator is not spinning lamp should be on, once spinning it goes off - exactly how you describe so all good and normal.

You haven't answered the question: how hot is the alternator getting?

steve m - 29/6/20 at 09:57 AM

Take the bulb out, and put the ignition on, does the alternator still get hot? as if it does, the bulb issue is not the problem

gavin174 - 29/6/20 at 11:06 AM

quote:
Originally posted by 02GF74

quote:
Originally posted by gavin174

the engine is not running yet,
but with the ignition on the alternator is getting hot.

I have connected it to a battery on the bench,
connecting the B+ to the battery and earthing the alternator everything is fine.

when I connect the switch live to the I terminal the alternator starts to heat up.

when I connect the L terminal to the negative side of a light and 12v to the other side of lamp,
spin the alternator with wheel nut gun the light goes out....

any ideas?

It sounds like you have wired it correctly.
wiring is like this:

when alternator is not spinning lamp should be on, once spinning it goes off - exactly how you describe so all good and normal.

You haven't answered the question: how hot is the alternator getting?

If i leave the ignition on, the alternator can get too hot to touch

02GF74 - 29/6/20 at 11:34 AM

quote:
Originally posted by gavin174

If i leave the ignition on, the alternator can get too hot to touch

ok, the alternator is mostly metal, I'm guessing at least a kilo, so a fairly chunky heatsink, getting that hot definitely does not seem right.

I have the tiny alternator fitted, not sure if it has the 4th wire for live but will take a look at some point and post back.

starterman - 29/6/20 at 06:38 PM

Give me a call if you want and I'll see if I can sort it for you.
01579 382391 Business hours.
Cheers
Mike

gavin174 - 30/6/20 at 08:53 PM

quote:
Originally posted by starterman
Give me a call if you want and I'll see if I can sort it for you.
01579 382391 Business hours.
Cheers
Mike

Thank you for your time today..

Very much appreciated.

CosKev3 - 30/6/20 at 08:59 PM

What's the outcome?

gavin174 - 4/7/20 at 06:37 PM

To put closure to this...

I have rewired the alternator,
So that the IG switch live is now controlled by the Omex 600.

I have taken the feed from pin 87 on the fuel pump relay.

This way the IG is only live when the fuel pump is running.

And now the alternator doesnt get hot.

Thanks for all you help.

starterman - 4/7/20 at 06:59 PM

Good man

CosKev3 - 5/7/20 at 07:40 AM

quote:
Originally posted by gavin174
To put closure to this...

I have rewired the alternator,
So that the IG switch live is now controlled by the Omex 600.

I have taken the feed from pin 87 on the fuel pump relay.

This way the IG is only live when the fuel pump is running.

And now the alternator doesnt get hot.

Thanks for all you help.

Only found out this week on these Densos the ignition live excites them,not the warning light.
So that's why yours was getting hot! : )