Electrical noise/interference?

Ive got a chevelle that Im working on with a push to start system that I cannot get a "glitch" out of... The PTS is super simple with a bank of relays and a single latching relay to latch the ignition on. The latching relay is a solid state that reverts to the un-latched position when it loses 12v. My issue is that the car will shut down randomly and Ive narrowed it down to the solid state relay losing power. The car is not actually dropping 12v though, Im thinking that it is picking up alot of electrical noise that is causing the relay to shut down for a millisecond and reset to its un-latched position. When the car does shut down, I can start it right back up again no problem. Im getting 12v right from the factory ignition switch harness and have a good ground on the steering column support. Ive tried putting a 100uf cap across the power and ground terminals and that did not make a difference. Tried a new relay also and got the same results. Ideas???

Try running the ground to the engine directly, a clip lead should suffice for test anyway.....ME, I'd just do it permanently, and up the value from 100mfd to about 500 or even 1000, especially if it's the lead that also powers the dizzy.....

Lemme know....

:smash:

mrvette said:

Try running the ground to the engine directly, a clip lead should suffice for test anyway.....ME, I'd just do it permanently, and up the value from 100mfd to about 500 or even 1000, especially if it's the lead that also powers the dizzy.....

Lemme know....

:smash:

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I just got a 1000mfd cap Im going to try... Also going to run a 12v feed direct from the batt and see what that does.
This car has 2 HID ballasts converting DC to AC for the headlights, and an MSD box, both of which I think are not helping my noise issues. Anything I can hook my DVM up to (and what reading it should be on) to look for noise while Im driving it? Id really like to prove that Im getting a spike or drop when this happens.
And this relay controls the ignition for the entire car, so yes it is shutting down the motor while driving :twitch:

vette427sbc said:

mrvette said:

Try running the ground to the engine directly, a clip lead should suffice for test anyway.....ME, I'd just do it permanently, and up the value from 100mfd to about 500 or even 1000, especially if it's the lead that also powers the dizzy.....

Lemme know....

:smash:

Click to expand...

I just got a 1000mfd cap Im going to try... Also going to run a 12v feed direct from the batt and see what that does.
This car has 2 HID ballasts converting DC to AC for the headlights, and an MSD box, both of which I think are not helping my noise issues. Anything I can hook my DVM up to (and what reading it should be on) to look for noise while Im driving it? Id really like to prove that Im getting a spike or drop when this happens.
And this relay controls the ignition for the entire car, so yes it is shutting down the motor while driving :twitch:

Click to expand...

Anything converting DC to AC in the way of a Solid state device is one dirty EMI/RFI SOB.....period, it will knock more shit off the air than you would imagine.....ME, I would go for a normal relay and bypass all that crap....now HOW to do it is not something I can immediately answer as I dunno anything about the 'rest of the story'.....

:thumbs:

Why don't you just put a timer on the relay trigger in parallel- if it surges-drops voltage the timer will still be supplying power - can dial in from a .1s to 30seconds

just a thought-

Richard

This looks like a quiet push to start system

Richard454 said:

Why don't you just put a timer on the relay trigger in parallel- if it surges-drops voltage the timer will still be supplying power - can dial in from a .1s to 30seconds

just a thought-

Richard

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The relay trigger is not surging, its the relay itself. Putting the timer on the trigger will create a scenario where I wouldnt be able to turn the car off if the timer was still active. And being a Solid State module, it may have the same issues as my current solid state relay with the interference.

I *think* I have it fixed with a new grounding location. Went for a ride today with no issues, going to try it again tonight with the HID ballasts on to see if that makes a difference.

Got it...I was thinking you set the relay for a second or two- wouldn't make a big difference shutting off the car.

Just for grins- put a meter measure AC at the power wire on the relay...turn on the lights - see if it goes up. OR the alt could be you problem to start w/. If it's showing more than .5 VAC at the output w/ a load on it that could be a culprit.

Richard

Richard454 said:

Got it...I was thinking you set the relay for a second or two- wouldn't make a big difference shutting off the car.

Just for grins- put a meter measure AC at the power wire on the relay...turn on the lights - see if it goes up. OR the alt could be you problem to start w/. If it's showing more than .5 VAC at the output w/ a load on it that could be a culprit.

Richard

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Ahhh good info on using the meter to measure AC Thanks!

vette427sbc said:

Richard454 said:

Got it...I was thinking you set the relay for a second or two- wouldn't make a big difference shutting off the car.

Just for grins- put a meter measure AC at the power wire on the relay...turn on the lights - see if it goes up. OR the alt could be you problem to start w/. If it's showing more than .5 VAC at the output w/ a load on it that could be a culprit.

Richard

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Ahhh good info on using the meter to measure AC Thanks!

Click to expand...

Years ago I got into it with some guy making PWM fan speed controllers and so put my Tektronics scope on the alt output 108 17SI on the vette....well the ripple is 700 mv.... call it .7 volts and that is enough to mess up his PWM controller, he wanting it run off the battery, which is bad practice...So I suppose the same sorts of problems exist with this unit.....

why is running it off the battery bad practice?

vette427sbc said:

why is running it off the battery bad practice?

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If you study a stock GM wiring diagram off most any car, they run the fans off the alt. output stud, almost directly.....reason is, that the charge wire to the battery terminal has a fuse or fuse link (thinner wire to act as a fuse) and allow so much voltage drop when the battery is badly discharged, limit the current/voltage at the battery posts....(ASSuming the connections are all fine the way they should be) so if you take a ~20-30 amp fan load across the battery posts, and the car is in traffic, the battery is seeing less than a full charge rate, which is 14.8 volts....so the thing is driven in traffic or short trip basis, and the battery is never really ever seeing 14.8 , instead the max it sees is like ~13 volts, the % drop in power/charge transfer is ASStounding, this is not a household with 110 volts, so +- 2 volts is nothing....a near 10% voltage swing is a LOT to a car battery....

IF you drive it only on long trips for maybe 30 minits between starts, it may well be ok, but the battery will never attain it's fullest charge....due to the voltage drop over the charge wires, and even if you jump the circuit with yet another wire from the alt. out stud to the battery directly, you still have some voltage drop when fans are on, which they are all the time with A/C running in summer, God help you if you running stereo and lights, and FI, and whatever....

That is the short form ANALysis of it from my scopes, and DVM's over the years.....

:smash:

Just to make sure : it does run for a while or does it shut off once it has started ?

Belgian1979vette said:

Just to make sure : it does run for a while or does it shut off once it has started ?

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:surrender: Sorry man, it was a .net discussion of some years ago, and I can't remember all the details, except the basics....it MAY have been just bad operation or maybe it blew the speed controller....I just believe in keeping it simple, a silly relay controller ran by either a temp switch or a FI computer seems to suffice....

:smash:

mrvette said:

Belgian1979vette said:

Just to make sure : it does run for a while or does it shut off once it has started ?

Click to expand...

:surrender: Sorry man, it was a .net discussion of some years ago, and I can't remember all the details, except the basics....it MAY have been just bad operation or maybe it blew the speed controller....I just believe in keeping it simple, a silly relay controller ran by either a temp switch or a FI computer seems to suffice....

:smash:

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I was thinking of a problem I had when I was getting my FI up and running; Had it wired to a wire coming from the ignition switch that was hot in run but not in start...take me a lot of time to figure it out. It's probably something else however.