Greetings 700 board;

[WTF, I swear I posted this on the 700 board but it wound up on the S90/V90...cockpit problem or what gives?]

I am regularly in the Brickboard vintage department (those models with B18/20 and SU carbs!). As I don’t hang out here much at all, this topic may very well have been previously covered...if it has and someone can point me to the appropriate archive location, I'll look there also...but our '90 740/B230FT has developed an interesting problem, which I would dearly love to eliminate...intermittent ignition noise on AM (it's really OK to listen to that sometimes!)...and before you say "Radio Noise Suppression Relay", please read on.

Background: A while back, we replaced the fuel-pump relay (by European Motors -a local independent - recommended) when a corrosion caused bad solder joint caused it to work intermittently, later, I found out that this is well-known issue, typical, and just about guaranteed on these models...(but not after the dealer: Mitchell of Simsbury CT UNECCESSARILLY replaced the fuel-pump and FPReg...thanks for screwing me, and living up to my worst expectations!). In doing a post-mortem on the failed relay, and confirming the bad solder joint, then checking over the repair work under the hood, I noticed the second "Radio Noise Suppression Relay" on the other shock tower, with an identical PN. I (couldn’t resist and) removed and carefully took apart this relay...sure enough, it had the IDENTICAL condition on the same terminal as the failed relay (souvenir pix available). I soldered this terminal, cleaned up the working contact a bit and reinstalled the repaired relay immediately noticing decreased ignition noise on AM.

New Problem: Since the repair work on the suppression relay two years ago, the ignition noise on AM has returned, but is now intermittent. I've noticed, that it is just about eliminated (for a while, but more accurately, until next time something electrical is switched) by stepping on brake, or activating sunroof. I am therefore convinced that the noise is caused by a marginal ground connection, which is temporarily being (microscopically) welded and made OK when a large current is passed through it. I am further convinced, that by cleaning the terminals on this connection to ground, and doing my anti-corrosive paste thing upon reassembly, I will take care of this annoying problem forever...now I suppose this MIGHT very well be happening at the working (or some other) contact WITHIN the suppression relay (again), so I defer to anyone with firsthand experience which they would like to pass along.

My questions are: Which connection is it, where is it located...has anyone experienced and fixed similar symptoms and can pass along some help. Also, can someone explain to me the function of the "Radio Noise Suppression Relay" specifically...I found it on the wiring diagram of the car, but cannot figure out by what means it does what its name implies (and what controls it). I see, that its working contact is tied into the injectors by way of individual "ballast resistors"...so maybe this has been an injector noise issue all along...in either case, Radio noise is radio noise, and I would love to understand it from an electronic viewpoint (and eliminate it!).

Thanks in advance for help!