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testing circuits and relays in race car #1519903 10/19/13 11:20 AM 10/19/13 11:20 AM
Joined: Aug 2007 Posts: 2,449 nc E earthmover OP top fuel
earthmover OP top fuel E Joined: Aug 2007 Posts: 2,449 nc	any of you guys use the power probe plus ???? or what do you like to use to fined bad circuits bad grounds in your race cars

Re: testing circuits and relays in race car [Re: earthmover] #1519904 10/19/13 12:04 PM 10/19/13 12:04 PM
Joined: Nov 2004 Posts: 4,330 Lynchburg, VA Leon441 master
Leon441 master Joined: Nov 2004 Posts: 4,330 Lynchburg, VA	Volt Ohm Milliamp meter. Is all I use earthmover Something for anyone reading this post who does not know. It is easy to get ahead of the basic principles. Here is a good start. Use voltmeter to check for potential difference. Meaning, you can put positive on battery or source end of circuit and negative on other side of suspected problem. If you have any significant voltage that is the drop in the circuit. Then you can keep spot checking until you find the area of the most voltage drop. Should be the device you are feeding commonly called the load. This is easy to do when you can reach both ends of the circuit. Use ampmeter on highest scale first not to blow the meter. Disconnect the wire from your buss and check the current. No current in electricity no results. Just like a stopped up faucet no current flow no water. Say you are working with a Fuel pump that pulls 7.5amps. The pump is running slow. You check voltage at the pump wires and you do not have better than 10V with a 12 volt system. You have a high resistance connection or bad wire in the circuit. Then you simply disconnect the wiring insert amp meter in series with the circuit. Record your reading. If it is lower than 7.5 amps. You may have a problem. Take a jumper and run it from your meter straight to the battery. If the reading is much higher you have a connection or wire problem. Remember the ground side is just as important as the positive side of the circuit. Leon Career best 8.02 @ 169 at 3050# and 10" tires small block power.

Re: testing circuits and relays in race car [Re: Leon441] #1519905 10/19/13 03:45 PM 10/19/13 03:45 PM
Joined: Mar 2006 Posts: 9,863 MI, usa dvw master
dvw master Joined: Mar 2006 Posts: 9,863 MI, usa	Quote: Volt Ohm Milliamp meter. Is all I use earthmover Something for anyone reading this post who does not know. It is easy to get ahead of the basic principles. Here is a good start. Use voltmeter to check for potential difference. Meaning, you can put positive on battery or source end of circuit and negative on other side of suspected problem. If you have any significant voltage that is the drop in the circuit. Then you can keep spot checking until you find the area of the most voltage drop. Should be the device you are feeding commonly called the load. This is easy to do when you can reach both ends of the circuit. Use ampmeter on highest scale first not to blow the meter. Disconnect the wire from your buss and check the current. No current in electricity no results. Just like a stopped up faucet no current flow no water. Say you are working with a Fuel pump that pulls 7.5amps. The pump is running slow. You check voltage at the pump wires and you do not have better than 10V with a 12 volt system. You have a high resistance connection or bad wire in the circuit. Then you simply disconnect the wiring insert amp meter in series with the circuit. Record your reading. If it is lower than 7.5 amps. You may have a problem. Take a jumper and run it from your meter straight to the battery. If the reading is much higher you have a connection or wire problem. Remember the ground side is just as important as the positive side of the circuit. Leon After finding low voltage I'll check each leg of the circuit. Such as Positive battery post to positive feed at a suspected item . Say you're testing for low voltage at the fuel pump . Positive battery post to the positive on the pump reads 1.5 volts. You have a 1.5 volt loss in that circuit, Now you back track. Test at the relay + to + and so on until the culprit is found. Woks on the ground side also. Always test with the circuit loaded ( component switched on). Doug

Re: testing circuits and relays in race car [Re: dvw] #1519906 10/19/13 08:19 PM 10/19/13 08:19 PM
Joined: Feb 2009 Posts: 1,532 off the grid 340B5 pro stock
340B5 pro stock Joined: Feb 2009 Posts: 1,532 off the grid	http://www.amazon.com/ESI-687-Amps-Current-Probe/product-reviews/B000W8HD6O I have the older version of this for checking relays, fans and pumps for current draw. Yeah, it's got a smallblock.

Re: testing circuits and relays in race car [Re: 340B5] #1519907 10/19/13 09:34 PM 10/19/13 09:34 PM
Joined: Aug 2007 Posts: 2,449 nc E earthmover OP top fuel
earthmover OP top fuel E Joined: Aug 2007 Posts: 2,449 nc	ok guys maybe I should have worded the ???? different.. I use to work for the power company was a super for 4yrs.. from house service to taps 13.2 and some 750 stuff....my mean ???? is is it a good tool to have before I pay the 120.00 for it.. I see it has so many different uses ...from checking voltage to finding grounds and testing stuff checking + voltage and - voltage, you can even check for voltage drop all alone as it holds all info until you reset it..so I am sorry for the misleading ???????thanks for all the tips and help....also I own and operate my own truck (dump) and thought it would be a great tool to help around on it as it comes with 2 20' leads you can test from 1 end to the other and not have to unhook everything..

Re: testing circuits and relays in race car [Re: earthmover] #1519908 10/19/13 09:37 PM 10/19/13 09:37 PM
Joined: Aug 2007 Posts: 2,449 nc E earthmover OP top fuel
earthmover OP top fuel E Joined: Aug 2007 Posts: 2,449 nc	http://www.ebay.com/itm/Power-Probe-3-II...f5d&vxp=mtr this is the 1 I was looking at...

Re: testing circuits and relays in race car [Re: earthmover] #1519909 10/19/13 10:45 PM 10/19/13 10:45 PM
Joined: Jan 2003 Posts: 27,421 Balt. Md 3 383man Too Many Posts
383man Too Many Posts 3 Joined: Jan 2003 Posts: 27,421 Balt. Md	I would also add when checking voltage at a unit in a circuit like a fuel pump always backprobe the wire or in other words leave the circuit and wires hooked up so you dont create an open circuit. If you unhook a unit and check voltage its not an accurate reading because you are checking open circuit voltage. And I agree voltage drop is the best way to check circuits. Ron Last edited by 383man; 10/19/13 10:46 PM.

Re: testing circuits and relays in race car [Re: earthmover] #1519910 10/20/13 03:50 AM 10/20/13 03:50 AM
Joined: Aug 2003 Posts: 43,252 Bend,OR USA C Cab_Burge I Win
Cab_Burge I Win C Joined: Aug 2003 Posts: 43,252 Bend,OR USA	Most automotive mechanics and most hot rodders don't know or understand current flow in D.C. circuits The current flow is from the negative side of the battery through the circuit and returns back through the positive side to the battery. Almost every one thinks the current flow is from the positive side of the battery to the negative side of the battery, it is not. The only time D.C current flows from the positive side to the negative side is inside the battery itself The grounds, the negative side connections, are very important if you want good current flow to start with Now for the consternation and debate All battery started cars are the same, all U.S. made cars that had 6 volt batterys had positive grounds, so did almost every other car and truck in the world. Why the Amercian auto makers decided to switch from positive grounds to negative grounds when they switch to 12 volt systems I do not know or have a hint why OP, is your dump truck positive or negative ground Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)

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