keeps blowing ignition amps

[georgenewman1]

  :sad:hi, as it says in the title, i am now on my 4th ignition amp. i have a 1990 mk 16v gti and about 3 months ago the battery went dead, i charged the battery and the car didnt start, traced it back and it turned out to be the amp, this was after replacing the ignition module, the coil the leads aznd the plugs, all the earths have been removed thougraly cleaned lubed and replced to the location they came from. the car runs fine when the amp is replaced but then after about 2 hours of driving it simply stops and loses spark and only restarts when the amp is replaced.

NEED HELP PLEASE cheers guys 

[danny_p]

there are 2 ways to kill an ignition amp they are repeatedly kicking it with big voltage spikes or getting it to hot.

if the earth between the coil and head is bad it can give the ignition amp stick, this is easy to check so worth doing anyway.

more likely is the the ignition amp is overheating ether due to a bad thermal connection to it's heatskink, the heatskink should be clean and smeared in heatsink compound where it will be in contact with the ignition amp.

the other cause of overheating is if the coil has started to breack down internaly a short in the LT winding of the coil can inceres the power consumtion of the coil but without appearing to affect it's functionality. eg if the winding is shorted half way  there are half the turns but twice the current will flow meaning actual power output of coil can show no advers affects but the large increse in current it's drawing will mean they gett hot and overload theer driver circuits whitch also get hot

[georgenewman1]

nice one cheers buddy, but may i ask where theis heat sink is and what it looks like, cheers

[rubjonny]

its the big metal bit under the amp. mk2 ones come in 1 piece and cannot easily be split, mk1 items have a seperate heatsink to the ign ampy bit. could be yopu are buying mk1 items and fitting direct to mk2 ecu bracket? that wouldnt give enough heat protection. also where are you getting them, id prefer to use an old gen vag one than a new cheapo pattern part.

as above tho, check the chunky earth cable between the back of the head and one of the coil mounting screws, and think about changing the coil for a new one (make sure you buy bosch!)

mk1 type:


mk2 type:

[georgenewman1]

rite i seem to be confused, ive been told by mr rac that this thingy in the pic was the ignition module, the bit that i keep braking is the big black box under the plate this thing sits on, i thought it was an ecu but was told mk2's dont have them and it was an amp, sorry for the confusion,  i replaced this as mattrer of course off of ebay but the old one still worked fine, the bit thats blown has a vacuum hose on it too if that helps
 cheers

[Diamond Hell]

the bit that i keep braking is the big black box under the plate this thing sits on, i thought it was an ecu but was told mk2's dont have them and it was an amp, sorry for the confusion

Sounds like an ECU to me.

[georgenewman1]

k im blowing the ecu all the time, and help im well stuck, cheers

[Diamond Hell]

Needs better earths.

Replace the strap from rocker cover to the coil.

[rubjonny]

the 16v does have an ecu for the ignition control, its k-jet 8vs that dont have an ecu at all.  check the gearbox earth,  make sure the connection is good, also check where it is earthed to. the earlier cars were earthed to the top metal bracket on the gearbox which isnt very good when the car gets old. the later cars the earth was moved from there to a stud on the rear engine -> gearbox mounting bolt.

[georgenewman1]

well the earths on the back of the gear box, but when you say the earth to the coil what exactly do you mean, i have one going from the head to the coil bracket, but nothin to the terminals on the coil itself