200QA suddenly no start, no spark - Solved!!!

[Ben Swann]

David,
 
You do need to have the coil well grounded - the transistor is a heat sink and that is
why it is connected to the firewall like that.  Probably the reason for premature
failure is that it was not secured to the firewall. 
 
Having the car together with everything working makes it far more valuable than having
all the little things needing repair.   Usually the cars are worth more to keep and
drive than you will ever get out money-wise.
 
Ben

  _____  

From: David Michael [mailto:adavidmichael at gmail.com] 
Sent: Monday, March 22, 2010 1:26 PM
To: Quattro List
Cc: Ben Swann; psdooley at verizon.net; 200q20v at audifans.com; audi at humanspeakers.com;
kentmclean at comcast.net; bob at chips-ur-s.com; cobram at juno.com
Subject: Re: 200QA suddenly no start, no spark - Solved!!!


At lunch time I checked that the b+ (track 15) was 12V and it was. So then I temporarily
hooked up my old coil (one connector, high tension lead and a ground clip) and the car
fired right up. 

"course when I went to install the old coil more permanently, I totally forgot that the
nuts on the back side of the firewall (in the plenum) are NOT captive, and they fell off
and rolled under the blower. Fortunately we have a metric screw cabinet at work..


While I can't be sure its the actual cause I suspect that, as a few folks had postulated
(along with Scott M's website), the transistor triggering unit went bad. Ironically,
it's a new unit I installed prophylactically about 4k miles ago. Infant mortality.....

BUT, I this is the last straw. It's time for her to go. I no longer have time to keep
up. Car runs like a freight train, but needs some peripheral work (window lifts, A/C,
etc) and I no longer have time and don't want to spend the money. Anyone have any idea
what a 200QA with 235k that is running extremely well but needs work is worth?

Thanks again to everyone for your help with this, and many other problems.....

Dave



On Sun, Mar 21, 2010 at 8:14 AM, David Michael <adavidmichael at gmail.com> wrote:


Thanks for all your suggestions. Based on what you all have said, I need to back the
diagnosis up a step and 1st make sure the coils is powered. SJM's website suggests that
it if the ignition switch can fail and stop powering the ignition circuit of the ECU. 

In any case, I will check 12V and use my LED tester to verify that the ECU is sending
coil triggering pulses to the coil. Though it will have to wait till Monday - car is
still sitting in the parking lot at work

Folks on this list are great. Only way I could have gotten to 230k....

Dave 


On Sun, Mar 21, 2010 at 3:17 AM, Huw Powell <audi at humanspeakers.com> wrote:




If what you mean is the coils don't fail that much, but the POS (transistor) does, then
that is correct. The problem is probably not the coil itself, but the Darlington
Transistor that is mounted on the coil, but generally the assembly is referred to a the
coil by most



The transistor failing is not the coil failing. Coils are incredibly simple. Measure
both sides. Good? then good. I'm running an old audi coil on my '57 Trojan loadster.
Made homemade ballast resistor. Works great.


-- 
Huw Powell

http://www.humanspeakers.com/audi

http://www.humanthoughts.org/