How to test the speedo light circuit?

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t0m1980

t0m1980

Active Member
Posts
264
Location
Kent
Good evening all,

Ive come to a dead end with this, so I’m hoping someone can help,
Done the TD5 dash conversion and the speedo lights do not come on, I’ve checked all the connections up to the plug and they all seem fine and I have bought new bulbs which I replaced, but still no joy! I even tried another gauge/speedo which didn’t work?
Can I put 12v straight to it to test them?
I tried the red and orange as a positive and the earth but as that didn’t work I thought I’d ask before I damage anything (presuming both gauges work ok?)
The mileage bit comes up fine, just no back lights

218E42D3-7F78-4267-A2C3-704F02C204E3.png


As always any help would be greatly appreciated
 
Last edited:
t0m1980 said:
Good evening all,

Ive come to a dead end with this, so I’m hoping someone can help,
Done the TD5 dash conversion and the speedo lights do not come on, I’ve checked all the connections up to the plug and they all seem fine and I have bought new bulbs which I replaced, but still no joy! I even tried another gauge/speedo which didn’t work?
Can I put 12v straight to it to test them?
I tried the red and orange as a positive and the earth but as that didn’t work I thought I’d ask before I damage anything (presuming both gauges work ok?)
The mileage bit comes up fine, just no back lights

View attachment 190928

As always any help would be greatly appreciated
Click to expand...

Are you using bulbs or LEDs? When I done mine, they didn’t light up straight away, partly due to being LED (wrong polarity) and partly due to not being fully fitted. You need a small deep socket, can’t remember the correct size, to fully seat the bulb holders. If they still don’t light up, have a look at the contacts on the holders as these can sometimes bend and not make contact with the PCB.

To test the lights, you should be able to put 12v direct to the sidelight illumination, and earth pins 2, 7, &9 (assuming you used the correct pin numbers).
 
mick 1986 said:
Are you using bulbs or LEDs? When I done mine, they didn’t light up straight away, partly due to being LED (wrong polarity) and partly due to not being fully fitted. You need a small deep socket, can’t remember the correct size, to fully seat the bulb holders. If they still don’t light up, have a look at the contacts on the holders as these can sometimes bend and not make contact with the PCB.

To test the lights, you should be able to put 12v direct to the sidelight illumination, and earth pins 2, 7, &9 (assuming you used the correct pin numbers).
Click to expand...
One has LED’s the other has normal bulbs, good shout with the socket, unfortunately my smallest which fits the bulb is too wide to go in the gauge.
Interestingly pin 2 is not yet connected to the transducer.... could that be the problem? Didn’t think it would affect the operation of the bulb, but my knowledge is poor!!

mystery said:
Yes got a better shot of all the pins are the plugs the same or are there locator's mould in the plug to stop inserting on wrong section assuming A and B View attachment 190942
Click to expand...

Hi Mystery,
It’s exactly the same as what’s in the diagram with regards to the pins and cable colours (excuse the state of it, I’m in the middle of cleaning it).
1DE155D3-BDDA-490F-B729-E693529C90ED.jpeg
AF9B2F4A-4746-4ABE-926C-C24C878EE92E.jpeg
 
HAVE YOU REPLACED THE LAMPS WITH LED OR ARE THEY STANDARD AND HAVE YOU GOT 12VOLTS ON PLUG' A' PIN 4 TO SUITABLE GROUND , 12 VOLTS ON PIN 4 TO THE BLACK WIRE PIN 7 PLUG 'A'
 
One gauge has LEDs, (which are such a pig to fit, I’m considering getting rid of them) the other has normal bulbs, I get 12v at 4 and 7 and if I stick the 12v at 4 and 7 on both gauges I get nothing..... so presuming both are knackered? I did try turning the LEDs round but it’s come out again and I can’t get it back in:mad: so I’ll try it with normal bulbs in a mo
 
So that’s both gauges with normal bulbs, pin 4 straight to + and pin 7 straight to -

Nothing, take it I need to go shopping?
 
mystery said:
HAVE YOU REPLACED THE LAMPS WITH LED OR ARE THEY STANDARD AND HAVE YOU GOT 12VOLTS ON PLUG' A' PIN 4 TO SUITABLE GROUND , 12 VOLTS ON PIN 4 TO THE BLACK WIRE PIN 7 PLUG 'A'
Click to expand...
If I didn’t have bad luck.... I wouldn’t have any!!
 
check each lamp before fitting with 12 v to confirm the do actually work out side the speedo then fit both normal lamp with the speedo unplugged see if you get continuity through pin 4 and pin 7, you should get a resistance reading of the two lamps ,if so attach with care a 12volt supply to the pins 4 and 7 to confirm the crimp connections ,can you see the actual contact areas the bulb holder locates on from the back of the speedo also have you any images of the mod done to the harness plug showing the wire colours from 300td1 connector and td5 new connector
 
mystery said:
check each lamp before fitting with 12 v to confirm the do actually work out side the speedo then fit both normal lamp with the speedo unplugged see if you get continuity through pin 4 and pin 7, you should get a resistance reading of the two lamps ,if so attach with care a 12volt supply to the pins 4 and 7 to confirm the crimp connections ,can you see the actual contact areas the bulb holder locates on from the back of the speedo also have you any images of the mod done to the harness plug showing the wire colours from 300td1 connector and td5 new connector
Click to expand...
Ok so I’m off to fraudsters to see if I can get some bulbs, top tip don’t move if you drop something :mad:
54553DFD-8A2D-4F16-9AE1-FE6C3E7E31F6.jpeg

7533BCF0-C760-4654-800A-3805CDC1B89D.jpeg

E39C3A97-F0D5-4169-BC0F-588994219563.jpeg

There don’t seem to be a problem with any of these, as of yet;)
 
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