Jump to content

Have I damaged my TR4A ammeter


Recommended Posts

Not sure what happened but some how, I noticed the ammeter peg hard full -ve discharge, then return to slightly -ve of zero. I find that original replacement Lucas 36313 ammeters are tough to find

Since that event, I observe that while all lights, indicators etc do show some discharge, only heater fan and high beam show any significant discharge to circa -20A. I have yet to see any +ve charge reading even with the cooling fan lights and heater on concurrently -  It's always starting from just off -ve zero, but never goes positive

By way of background, I have just fitted a Denso three wire (B, Light and 12v) alternator and narrow belt conversion and an electric fan. The fan power is through 30A fuse direct to battery, so probably won't show on the ammeter I guess - still have to figure that one out.  The alternator charge feed is to battery via solenoid and  the 12v sensing/field supply is a switched line from the fuse box (white terminal).

Also, I have now had the regulator in the alternator replaced and checked out - probably my fault, as when I first installed it, I simply took the 12v sensing/field supply directly from the alternator power post which even though permanent power, I thought it would be OK (according to internet searches this works for GM 10Si units). When the alternator had a low sounding hum I knew otherwise, so not good for Denso I guess. Now when running I get 15.4V reading at the battery so alternator now seems OK, but nothing shows on the ammeter....

A bit frustrating so wondering if the ammeter is damaged?

Cheers,

Alf

 

Link to post
Share on other sites

Something not right with your alternator if you see 15.4 at the battery, that will cook the battery (potentially literally overheating it) you want 13.8 for a lead-acid, potentially going as high as low 14.x, but never 15. The B wire should go staight to the battery, this B/sense wire is important to prevent overcharge. If you still have 15.4 in that situation then sounds like regulator in alternator is fried.

I cannot comment on the ammeter without a wiring diagram, but these are hardy instruments, i doubt you could damage it unless it got wired in series with the starter. In any case, you really need a voltmeter in place of ammeter to get any useful info on state of an alternator charging system.

Edited by ctc77965o
Link to post
Share on other sites

Your alternator wiring sounds like mine. Direct output from alternator to the battery cable at the solenoid.

I get little or no positive deflection of the needle.  Negative does shew for original wired ignition switch controlled items like wipers etc.  All my accessories and headlamps are wired through fuses that come direct from the battery.

I run a volt meter plugged into the cigar lighter and that is my yard stick for if the alternator is charging.  The voltage running is 13.5-14.5

Cheers

Peter W

image.png.3a7a56d5d81100f88d8fd3eb1f5c17dc.png

Link to post
Share on other sites
13 hours ago, silverfox4 said:

The fan power is through 30A fuse direct to battery, so probably won't show on the ammeter I guess

On the contrary Alf. When the fan is on with the engine running, that 30A should show as a charge if the alternator was connected correctly - but it isn't.   You have connected the alternator direct to the battery at the solenoid which means there will never be a charge shown on the ammeter but it will always show discharge whenever you switch something on even with the engine running. Both the alternator output and the cooling fan should connected to the downstream side of the ammeter away from the battery if you want it to indicate correctly.   

 

charge.jpg.c3111ca6ee555b7657d80e431e4e8c1d.jpg

As Dave says, that very high voltage reading is concerning and could damage the battery.  There seem to be several varieties of Denso alternator with different connection requirements - what type is yours?

Edited by RobH
Link to post
Share on other sites

Hello, how do you test an ammeter?, my thoughts are that somehow you need to draw various currents to check the deflection but how you do it I have no idea, I have a meter so can take readings, cheers, Andrew

Link to post
Share on other sites

 

8 minutes ago, AndrewMAshton said:

Hello, how do you test an ammeter?

Do you mean when installed in the car Andrew or as a stand-alone meter?

Link to post
Share on other sites

Slight correction to your diagram needed Rob.

The ignition circuit its self is not fused (white wires),  other circuits coming from the ignition switch are fused, & the wire colour becomes green.

Bob. (call me Mr pedantic !)

Link to post
Share on other sites
1 hour ago, Lebro said:

Slight correction to your diagram needed Rob.

Quite right  Bob - wording amended. The colours were not supposed to reflect the actual ones - it's much too difficult to draw colour stripes unless you spend a lot of time messing about :unsure:.  It was just to show the general connection arrangement. 

Edited by RobH
Link to post
Share on other sites
49 minutes ago, AndrewMAshton said:

Hi Rob, it is out of the car

Well to check the ammeter you will need suitable loads as you say Andrew. It isn't a precision meter so any readings will be fairly approximate.

The easiest loads to use are probably headlamp bulbs. A 60W bulb will draw 5A from a fully-charged car battery so if you have a couple of those you can check at 5 and 10 Amps.  Reversing the meter connections will check both charge and discharge directions. 

It might be an idea to make the battery connection through a 20A fuse to prevent calamities.  

Connect battery + to one end of the ammeter through the fuse, connect the other ammeter terminal to the bulb and connect the bulb body to battery -.  Swap over the connections to the ammeter for reverse deflection. 

Repeat but with two bulbs connected in parallel as the load for the higher current.

If the bulbs are 55/60W dual filament you could connect both filaments at the same time on both bulbs. That would give a current of 19Amps for all four filaments in parallel. Bear in mind the bulbs are going to get very hot and you will need suitably thick connecting wire.  

Edited by RobH
Link to post
Share on other sites

Thanks very much for all the input

The first challenge then is to sort out the 15v charge rate and its potential impact on the battery. I had just picked up the alternator after having the regulator replaced and after installing I started and checked the voltage at the battery, and it was 15.4v - will have to this up with the Alternator supply shop  Stationary the battery voltage is 13.5v

First I'll charge the battery to full capacity with the charger, then try it again as hopefully the alternator should not be sending any charge after start-up, then I'll try a different multimeter.

Thanks again,

Cheers, Alf

Link to post
Share on other sites

Forgot to add that the wiring is confusing to me so will have to work through that.  The PO did the Alternator conversion back in 2000 based on the Dan Masters recommendations using the GM 10Si alternator which is quite large and cumbersome with the wide belt, so  I have changed out to a Denso type and narrow belt (probably Chinese copy now that I think about it as their are no name plates or other identifiers on the unit)

This is a challenge worthy of these restrictive Covid times.

Cheers,

Alf

Link to post
Share on other sites
9 minutes ago, silverfox4 said:

Stationary the battery voltage is 13.5v

If by 'stationary' you mean that is the battery voltage with the engine off - it could be your voltmeter is over-reading as the battery shouldn't be that high.  A fully charged lead-acid battery should not exceed 12.8v when off load.  

If your meter does overread by 0.7 v that reading of 15.4v when on charge may actually only be 14.7v, which is normal for an alternator intended to charge 'calcium' batteries which need a bit more than straight lead-acid. 

Link to post
Share on other sites

Thanks Rob that's interesting.

I just went out to check status and fortuitously the battery charger was showing full charge, so with the charger still connected the reading was 14.85v.  I disconnected the charger and checked again -  14.44v, off-load as you say. After waiting ten minutes it was 14.27v but will check again in an hour or so in case there is further residual effects from the charger. I should note that before connecting the charger this morning, the battery reading was 13.8v and seems to vary around the 13.5-13.8v

 Clearly this does not compare to the 12.8v off-load for a fully charged battery, and suggests that my meter is over-reading maybe by as much much as 1.0v

I am going out to purchase another meter - will follow up later with what transpires.

Cheers,

Alf

Link to post
Share on other sites

I think you nailed the off-load battery voltage problem Rob and Dave!

Just back from shopping :), and did another check.....

First meter reading - 14.24v

New meter - 13.21v

Borrowed neighbour's meter - 13.17v 

Still higher than the 12.8v for an off-load battery voltage, but not much I can do about that, so hope it's OK. I will wait until tomorrow to start it and get the alternator charging and load readings 

IF that works out OK I can turn to the ammeter wiring side relative to Rob's diagram. I may have to post some pictures on that to solicit further guidance

It's a pain when you cant' trust your "electrickery" tools, which is not my strong point to begin with....

Cheers,

Alf

 

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.