Jump to content

Recommended Posts

The 15ACR which was standard on the early TR6,  is rated at 28Amps at 6000 alternator rpm (3200 engine revs). The  17ACR on the later cars gives 36Amps at the same speed. 

There is no easy way of testing them properly on the car and anyway to do so needs some test-gear like large variable resistances for loads

The simple check you mention will tell you whether it is working though, and generating at least 10 Amps.  With the engine off and the headlights on there should be a 10A discharge shown on the ammeter.  With the engine running at above 3000rpm this should fall to zero and depending on the battery condition may even become a charge to the battery.  

If the discharge current does not fall or does so only partially, the alternator is not working properly. 

 

 

 

Edited by RobH
Link to post
Share on other sites

Volts is a good indicator...use a voltmeter on a ~20V DC scale...your battery and headlamps are sufficient load to ensure the voltages are meaningful. At 3200 revs you should have 13.8V measured at the battery...if you have that then the alternator and wiring are good.  If you see a number greater than ~14.2 V then that is a concern about either wiring or alternator health, similarly numbers under 13V indicate that the system is not charging (could be alternator, could be wiring).

Edited by ctc77965o
Link to post
Share on other sites
  • 3 weeks later...

I would be very concerned if my engine had to be doing 3000 rpm in order that my alternator could provide sufficient output to drive the headlights and a few other items.

On my TR4, I have narrow belt conversion and a Lucas LRA101 alternator (later sold as Unipart GXE8210) as fitted to the TR7, which it is rated at a modest 34 amps.

With the engine running yesterday, it kept the ammeter in its usual very slightly positive reading with the engine at 1300 rpm and full-beam headlights (plus sidelights), both spotlights and the heater motor running.  That is the sort of performance I expect of an alternator.

In stationary traffic, with dipped headlights, the ammeter only goes slightly negative when the engine is running below about 800 rpm.

Ian Cornish

Link to post
Share on other sites

I imagine that  the passage of time has brought superior electronic components, and that this may have permitted the output of alternators to be increased without fear of damage.

Three years ago, I bought a spare equivalent of the LRA101 from ATP Electronics and it is rated at 50 amps, a lot more than the original 34 amps.  It has code ALT113 Left hand (although it sits on the right of a TR2/3/4 engine, it must be lefthand).  The full code was 7JN19557MJ614343Y.  As the unit is unused and sitting on the shelf, I cannot say anything more than that it looks good and was a competitive price.

Ian Cornish

Link to post
Share on other sites
On 11/21/2020 at 4:17 PM, ed_h said:

The original 18ACR on my TR6 was rated at 40 amps, but the replacement 18ACR I bought recently claimed 60 amps.

Ed

Just fitted one supposedly updated to 65 Amps as a replacement to the 15ACR in my 1970 TR6

Link to post
Share on other sites

Chris - as I posted on another thread, it isn't the alternator which determines the current flowing, it is the load. The alternator only supplies what it is asked for and do not forget that the battery can supply a lot more current than any alternator.  The wiring is adequate for all the standard loads so if they have not been changed there is no concern if a larger alternator is fitted.  

What would be of concern is if a load has been increased without a commensurate upgrade of the connecting wire. 

 

 

Edited by RobH
Link to post
Share on other sites

It seems that the main output conductor from the alternator should be sized based on the current rating of the alternator.  With a severely discharged or faulty battery, the alternator may supply all the current it is capable of.

I upgraded that wire to 120 strand.  With PVC insulation, it is rated at 60 amps. I think 120 strand is close to AWG 6.  An alternative is to run parallel wires. Many Lucas alternators have a pair of large male output spades that are electrically connected.

Ed

Edited by ed_h
Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...

Important Information

Please familiarise yourself with our Terms and Conditions. By using this site, you agree to the following: Terms of Use.