My question is why will my dual filament bulb not work in the holder of the new rear lights . Why will the bulb push down , tightly , but not twist round as it should , regardless of which way round it's inserted . Does it require a slightly different bulb or are the holders of an inferior design and poorly made . That's basically it .

Hi
Well, thats a mystery for sure but there are different types of twin fillament bulbs and holders.
Just to make life difficult o_O

Std twin fillament (stop/tail) are BA15D and BAY15D (#1157) - the BA15D won't fit in a BAY15D holder (and vice versa).
LandRover use the 1157 BAY15D P21/5W bulb, this is identified by having the opposing pins at different heights. This is to stop you putting the bulb in about face and having a dimmer brake light.
The bulb used in indicators and side lamps is the BA15S (S for single filament)

Just found this look .... https://www.bulbamerica.com/pages/what-is-the-difference-between-a-ba15d-base-and-a-bay15d-base1157
 
Hi
Well, thats a mystery for sure but there are different types of twin fillament bulbs and holders.
Just to make life difficult o_O

Std twin fillament (stop/tail) are BA15D and BAY15D (#1157) - the BA15D won't fit in a BAY15D holder (and vice versa).
LandRover use the 1157 BAY15D P21/5W bulb, this is identified by having the opposing pins at different heights. This is to stop you putting the bulb in about face and having a dimmer brake light.
The bulb used in indicators and side lamps is the BA15S (S for single filament)

Just found this look .... https://www.bulbamerica.com/pages/what-is-the-difference-between-a-ba15d-base-and-a-bay15d-base1157
. The bulbs are correct and the slots in the holder correspond . They are just tight to push in and won't turn . I suspect a manufacturing fault . Hope to get a reply from seller tomorrow .
 
The two contacts on the base of the bulb should contact the two springy things in the bottom of the bulb holder.
Earth is by the metal side of the bulb & the pins.
Usual stop/tail bulb in UK is 380.

Going on your bulb chart, the 1157 pictured here (1) as an LED shows a base diameter of 15.24mm whereas this (2) showing the 380 shows 15mm.
1. 1157-cw1w-g-main-body-digimark.jpg (950×734) (d114hh0cykhyb0.cloudfront.net)
2. CIT380.jpg (400×400) (eurocarcare.net)
Got a micrometer or caliper to measure the bulbs you've got?

It's possible to put a 380 stop/tail bulb in the wrong way round pin-wise
Ever been behind a car with one very bright taillight & one normal brightness & wondered how they've achieved it?:)
 
The two contacts on the base of the bulb should contact the two springy things in the bottom of the bulb holder.
Earth is by the metal side of the bulb & the pins.
Usual stop/tail bulb in UK is 380.

Going on your bulb chart, the 1157 pictured here (1) as an LED shows a base diameter of 15.24mm whereas this (2) showing the 380 shows 15mm.
1. 1157-cw1w-g-main-body-digimark.jpg (950×734) (d114hh0cykhyb0.cloudfront.net)
2. CIT380.jpg (400×400) (eurocarcare.net)
Got a micrometer or caliper to measure the bulbs you've got?

It's possible to put a 380 stop/tail bulb in the wrong way round pin-wise
Ever been behind a car with one very bright taillight & one normal brightness & wondered how they've achieved it?:)
Ratae , you did well finding those diagrams . Nevertheless I do have the correct bulbs and after endless repetitive fiddling I managed to get them in and turned . They are both in the correct way , the highest pin on the bulb slotting in to the highest keyway on the holder . I now have two tail lights and two brake lights operational . Unfortunately , not necessarily in that order , or at the right time .. With the lights turned off , I can get one brake light and one tail light to come on when I press the pedal . With the lights turned on I have one tail light and one double lit up with brake and tail light . When I press the pedal the other brake light joins the party . The left hand light is the one acting up . Here's some pics of the lights I ended up with , I should looked further and got the original type .
IMG_20220110_134701743_HDR.jpg
IMG_20220110_140318207.jpg
IMG_20220110_134746320.jpg
 
They are the old style series bulb holders (not 300tdi) and they need an earth. This is the copper piece you see on your first picture. This needs a (self tapping) screw through that into the panel behind to provide an earth into the body shell/tub..

Personaly i'd ditch those and fit the correct ones.
 
The copper strip is the earth.
When you turn on one light & it causes another to light it's almost invariably an earth issue
 
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Final update . The bulb holders are indeed poorly made . If I connect two nails to the pins in the holder and then touch the bulb to the nails it lights up correctly . So the bulb clearly isn't seating properly . I'll replace both lights with the original type .
 

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