side lights flash with indicators ( LED)

[impco lpg]

the description and the diagram I get, ITS THE MULTIMETER I HAVE NO EXPERIENCE WITH
I have a pic of the multimeter I have is it set right ?
sorry to sound dumb

[bd]

It appears to be set correctly to DC volts and has auto-ranged to the millivolt scale.

[impco lpg]

battery side.  right turn : high reading 168.4 low reading 148.1
                    left  turn  : high reading  94.0  low reading 83.7

with hazards on. right side : high reading 189.2 low reading 150.2
                         left side  :  high reading 105.7 low reading 83.7

[bd]

battery side.  right turn : high reading 168.4 low reading 148.1
                    left  turn  : high reading  94.0  low reading 83.7

with hazards on. right side : high reading 189.2 low reading 150.2
                         left side  :  high reading 105.7 low reading 83.7

Respectfully, the posted numbers are meaningless without the units of measure.  Are the readings in mV?  What is "battery side?"

The threshold voltage (minimum voltage drop (V₀) needed to force current flow through, hence luminescence from, an LED) for red LEDs lies within the range: 1.6 - 2.1 volts.  You need to clarify your responses.

[impco lpg]

all the readings given are in millivolts.
battery side, is location of battery (passenger side fender)

[bd]

I've been trying to wrap my arms around your description of the symptoms to determine what the exact cause and solution are.  Your measurements indicate there are less than perfect grounds in the forward turn/park lamps.  The manner in which the LED tail lamps tie into the front park lamps results in a voltage divider configuration whenever the turn/hazard lamps are energized.  Under these specific circumstances the resultant voltage applied across the tail lamp LEDs (~4 volts net across the LEDs with current limiting resistors) barely surpasses the LEDs' threshold and illuminates them.  I think the voltage divider configuration is the cause of the symptoms, exacerbated by the less than perfect grounds for the forward lamps.

Assuming you've described all of the symptoms (haven't left any details out), a 1N5402 3-amp diode installed in the brown "park lamp" feed wire, between the forward lamps splice and the bulkhead connector with its cathode band orientated toward the forward lamps, should isolate the LED lamps and prevent cross-feed.  A possible complication might be introduced by the physical placement of the rear lamp harness tie-in to the lighting circuits in the engine compartment.  The diode needs to be located between the tie-in of the rear lamps and the splice to the forward lamps.



Edit: added quantitative information

[bd]

And, correct the grounds to the forward lamps.

[impco lpg]

i have ordered these
 http://www.ebay.co.uk/itm/10-x-1N5402-Rectifier-Diode-3A-200V/253036700226?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649

regarding the forward turn/park lamps GROUNDS, am I looking for the volt meter readings to be equal/similar to each side LH/RH.
not one side higher than the other ?

the only other thing I have not mentioned is, there is an alarm system fitted. that does the door locks/windows and ignition cut off. when the alarm goes off, as well as a siren tone it FLASHES the side lights. and when a door is opened. (using the door switch) could this be a problem ? alarm wire diagram pic below

[bd]

regarding the forward turn/park lamps GROUNDS, am I looking for the volt meter readings to be equal/similar to each side LH/RH.
not one side higher than the other ?

The measured voltage drop across the ground paths to the battery negative post should be as close to zero as you can get it.  This is true for all low- to medium-current grounds (<25 amps).  Be sure to perform a thorough inspection of the wire condition and wire-to-terminal connections.  Oxidized or frayed wiring should be cut back, cleaned, re-terminated and soldered using 60 Sb/40 Pb or 70 Sb/30 Pb rosin core solder - or entirely replaced, terminated and soldered.

Take an inventory of the vehicle grounds and service them all (thoroughly burnish them then coat liberally with water rejecting antioxidant paste).  You should find the following vehicle grounds (recommended wire size is included for any ground paths that need to re replaced or fabricated anew):

• battery to engine (2 gauge)
  
  
• battery to right (passenger) frame rail (10 gauge)
  
  
• battery to radiator support (10 gauge)
  
  
• back of right cylinder head to cabin firewall (5/16" braided strap or 10 gauge)
  
  
• dash lighting and interior appliances to cabin left kick panel sheetmetal (various 18 to 16 gauge)
  
  
• rear lamps to bed (18 gauge)
  
  
• bed to right frame rail (14 gauge)
  
  
• cabin firewall to engine compartment hood (bonnet) (1/4" braided strap (preferred) or 12 gauge, suitably placed and long to allow opening and closing of the hood without catching, excessive flexing or stretching of the wire)
  

Additional primary ground connections are okay.  If any of the recommended ground connections are missing, fabricate and install them!

I doubt that your alarm is an issue.

[impco lpg]

just an update I only have 3 of the 8 earth/grounds you have listed 

NO battery to right(passenger) frame rail
     back right cylinder head to cabin firewall
     rear lamps to bed
     bed to frame rail
     cabin firewall to hood

I am going to make all the above, and cut out the white connectors and solder. and see if this makes any difference as it will.
NOT A GOOD START;

[bd]

[absent grounds...]

     battery to right (passenger) frame rail  -  this one is important as the primary extension of the main vehicle ground
     back right cylinder head to cabin firewall  -  this primary ground ensures the cabin is adequately grounded in support of all interior and cabin mounted electrical appliances
     rear lamps to bed  -  ensures the rear lamps are suitably grounded; alternatively, you can ground the rear lamps directly to the right frame rail
     bed to frame rail  -  ensures the bed is suitably grounded in support of the rear lamps
     cabin firewall to hood  -  (optional) helps manage radio "zzzzzzz" and provides a stable ground for an optional hood mounted engine compartment lamp

...NOT A GOOD START;

Actually, you are off to a GREAT start! 

The purpose for all of the primary ground connections is to ensure that "ground" is zero [earth] everywhere in the vehicle.  If that zero reference isn't consistent and at the same electrical potential throughout, all manner of ill will can befall you.  You'll begin to believe your truck is haunted!  Good grounds are vital for a happy vehicle!

[impco lpg]

i have fabricated new earths/grounds that where missing from your list, and now have ZERO reading earth/grounds to all . I also have removed the white connectors, and have soldered them and shrink wrapped (pic 1). the problem still persists (hazards only fault)   
pic 2 shows bulk head connectors,(4 wires right bulkhead connector rear lights, 5 wires  left bulkhead connector front lights) due to the way this has been wired at the white  junction box. only the white wire earths/grounds tie in to front and rear lights at this point. I am unsure as to the correct location of the 1n5402 diode as per your drawing, due to lack of front and rear tie-in

[bd]

Are the first and third pics of the same junction box, and does the junction box strictly serve the wires running to the rear lamps?

[impco lpg]

yes the pics are the same junction box (drivers side  fender)
both bulkhead connector wires  enter this junction box

top entry is right bulkhead connector in and rear wire loom out
side entry is left bulkhead connector in

[bd]

Isolate the brown wire that splits and runs to the left and right forward lamps.  The brown wire is the park/running lamp feed.  Do any wires from the rear lamps splice into this brown wire?