Testing relay boards...., Can you bench test a 914 relay board....??? Options

[second wind]

Hello out there....my car has been dying after getting a good warm up but starts the next morning. The tell tale symptom is that the fuel pump does not run when the stall occurs and even after hours of cooling off it still does not start...but it does in the morning....???
So talk on the street is the relay board is too old to work properly.....the description of 914 LTD's improved and rebuilt relay boards matches the symptoms of my car perfectly so as soon as I scrap up the money I will buy one.....meanwhile I have two spare relay boards and one looks really good. Is there a way to bench test the relay board before I swap the boards ?? These cars sure keep you on your toes and a relay board with fresh soldered connections sure sounds appealing so Brad is holding one for me. So back to the swap out....I hate to go to the effort just to install another faulty board. Look forward and appreciate any and all comments and help....thank you very much!!!!
gg

[Superhawk996]

OK -- so now about the S10.

Sounds an awful like you may have a pretty large short somewhere in the S10.

1) A short would draw down your battery to some level lower than 12v and of course will drain the battery over time if left connected.

2) A short in the S10 COULD have been what collapsed your 914 battery (assuming it was good as you've assumed) to the point that it could barely light the S10 dash lights but yet the S10 could be jump started with a larger current source (the other car's alternator).


By definition a complete zero ohm short circuit will measure 0 volts if you measure the voltage drop across the short circuit.

WARNING - DON'T TRY THIS AT HOME KIDS!

If we were to take a good heavy duty copper cable about 2AWG and directly short the 12v + terminal to the 12v negative terminal while measuring the voltage of the battery with our DMM, it would read 0 volts. There will be a (IMG:style_emoticons/default/stromberg.gif) ton of current flowing but the voltage measured across the + and - terminals will be 0v (assuming resistance of the cable is ZERO ohms). The cable won't be absolutely Zero ohms but it will be darn close.

Think about that for a moment and let it settle in.

A short like that - in its most extreme case can pull a 12v battery very close to 0 volts. Lesser shorts can pull it to 11v, 10v, 9v . . . . all depends on the particulars of the short.

I've had to demonstrate this to people (wearing protective gear) because folks refuse to believe it.