Bad Starter Relay?

[Zeppelin264]

Hello, I'm battling this weird electrical issue that I just cannot figure out. I have a 68' Coronet and using the stock style starter relay with the post which I'm using like a junction box to power the Sniper and a few other things (I know this isnt a good idea, re wire is coming soon). Whats weird is battery shows 12.6, alternator lug shows 12.6, starter relay post shows 12.6 etc... I start the car and the voltage at the alternator and starter relay post are jumping all over the place. 2v, 3v, 8v, 14.5v, 12.5v. The battery maintains around 13.5-14v as expected.

I started hunting down all the grounds and they all seem to be clean. I have many grounds between the block and chassis, also a ground from the 1 wire alt to the engine block. So my questions is: could the starter relay be grounding out internally and making the whole electrical system jump around like this? This has to be some kind of grounding issue as its only happening when the Sniper is running the engine, otherwise, everything shows battery voltage when car is off.

I even went as far as disconnecting the alternator, fire the car up and it does the same thing, just without that 13.5v+ input. Was thinking it was a voltage regulator back feeding or something. I also have a few relays in the chain of power for the Sniper unit, could a bad relay do this and still function? Maybe its the Sniper unit itself, it is brand new, just got it fired up last week. Its the Sniper 2, I had the Sniper 1 and it ran fine for many years and just decided to upgrade it recently.

 

[Koenig1425]

I would not suspect the Starter Relay to fail like that. If it internally shorts to ground...you'd know it. Battery voltage is connected directly to it. Suggest triple checking all of your new connections. Are your lights flickering? Amp gauge acting differently? Any other issues? I know my inexpensive Sears multimeter will sometimes provide erroneous reading around the distributor. I'm using MSD 6AL. I suspect the MSD is causing those erroneous readings.

 

[pnora]

Hello, I'm battling this weird electrical issue that I just cannot figure out. I have a 68' Coronet and using the stock style starter relay with the post which I'm using like a junction box to power the Sniper and a few other things (I know this isnt a good idea, re wire is coming soon). Whats weird is battery shows 12.6, alternator lug shows 12.6, starter relay post shows 12.6 etc... I start the car and the voltage at the alternator and starter relay post are jumping all over the place. 2v, 3v, 8v, 14.5v, 12.5v. The battery maintains around 13.5-14v as expected.

I started hunting down all the grounds and they all seem to be clean. I have many grounds between the block and chassis, also a ground from the 1 wire alt to the engine block. So my questions is: could the starter relay be grounding out internally and making the whole electrical system jump around like this? This has to be some kind of grounding issue as its only happening when the Sniper is running the engine, otherwise, everything shows battery voltage when car is off.

I even went as far as disconnecting the alternator, fire the car up and it does the same thing, just without that 13.5v+ input. Was thinking it was a voltage regulator back feeding or something. I also have a few relays in the chain of power for the Sniper unit, could a bad relay do this and still function? Maybe its the Sniper unit itself, it is brand new, just got it fired up last week. Its the Sniper 2, I had the Sniper 1 and it ran fine for many years and just decided to upgrade it recently.

Try another known good meter and see what its doing.

 

[Zeppelin264]

Good point! I'm using a cheaper volt meter. I will grab my nice one from work and try again tonight.

The way I discovered this is the Sniper is losing its ECU power and it flashes 11v randomly but stays running. This forces the o2 to reset and the engine starts to hunt for a short time which makes the engine run weird.

It could be the Sniper for all I know, but the wiring is something I need to look at closer and inspect.

 

[twecomm]

It's very common for folks to only own a digital meter to troubleshoot automotive problems. They can provide erroneous measurements depending on the quality of the digital meters design and what's being measured. I own both, cheap and expensive digital meters. If in doubt, I prefer my old school analog meter. I have had a Simpson 260 volt ohm meter for well over 45 years. Analog with a needle that moves over a scale, accurate and trustworthy for a "second opinion".
A cars DC electrical system can actually be quite "dirty" with AC alternator ripple, ignition switching spikes, EFI controller spikes and other electrical devices causing impurities of the DC. These issues can confuse digital meters. Think of it as never seeing anyone other than one doctor where the diagnosis is terminal. You owe yourself to get a second opinion.
Also, it's not likely that a starter relay could survive any type of an internal short. It's connected directly to then battery, no protection, a short would vaporize the relay in short order.