When you push the button, the leads become a substitute load and if the wire is free of added resistance, the voltage doesn't change (much). If the voltage does drop when you load the circuit (push the button) there has to be a series resistance in the wire. Make sure, when possible, you remove the load and test there, with both probes in exactly where the component was. That way you test 100% of the circuit. THEN drop the black probe to ground. Repeat the test. This isolates from (+) to (-).
Don't forget some failure analysis... "Burned" wires need heat. Current can only cause heat if it flows through a resistor. The fault was at a resistor. Wires should have no resistance, and thus, no heat. Where did the heat come from? Just the resistor? Was the wire corroded? Water leak? Defective? Old? Think the problem through so you can get a clear picture of what you think is the exact cause of the failure. Don't just fix it and move on - something caused it. Is there a larger problem?
Excellent! Great job. This is important because it's another example of ASS - "Always Something Simple". Think about the diagnostic steps. Did the fan work at all? Yes. Not the fan. Not the circuit. Not the relay. Not the fuse. Not the ground. Maybe the switch. Maybe the resistors. This is a good example of keeping your head screwed on tight and not letting the situation get the better of you. It's hard to focus if you're worried about time. How long did the diagnostic AND repair take?
Hi dan excellent piece of meter, I just got the whole set for father's day as a gift from my family ,I'm very happy ,but I haven't used yet,I have a concern, I got a Toyota 1989 22r and I'm replacing the alternator , can I check the single b+ cable once is disconnected from the alternator for voltage drop, since is a single wire? And please tell me how,thank you Dan , and don't listen to haters,see you from San Diego ca, usa
Everardo Camacho You can - technically - but it's better to simply read Bat B+ to Alt B+ with the voltmeter, since the terminals are exposed, AND, it's the REAL value. The battery needs at least 13.8V to charge. Let me know if you have questions - DS
Hi dan me again, I'm confused how do we know, when we are reading true voltage if the circuit had short_to ground or has continuity, they both test reads zero ? Can you please show me the difference of both of them ? I hope you understand question, excellent videos I'm learning a lot like never before, see you from SD CA
Everardo Camacho They don't read "zero". An OPEN reads "ghost voltage" - the meter reading flops back and forth and is NEVER zero. TRUE ZERO volts really is 0.0V. Try is with your meter. If you don't see a difference, it is likely you have a manually ranging meter. Put the meter on 20mV or 200mV and you should see a difference. Let me know.
Greetings you have very informative videos. l have a issue that I cant understand. I have a issue with my Dodge 09 Journey Master door switch. I can operate the back two windows, but cant operate the front two or any of the other buttons on the switch? Do l have a Bad relay..Ps. fromt time to time the buttons all work..then nothing for mts.. I'm confussed..HELP Thx.
hello sir I am writing from Uruguay sullivan eh seen your videos and I think facinanate and I would like to expand my knowledge and am q auto electrician, I wonder if there is a Spanish version of his book and I would love to have it for q utilisarlo as a reference book. I hope your answer soon. ps sorry x the translation but I'm using the google translator from already thank you very much
Thank you to replied so fast, I understand ghost voltage, what I don't is how can we check continuity with the meter on DC volts, check page 156 and 157 of fet book , I don't know how to tell the different when is short to ground or continuity, may be I'm a little burro hahaha
Everardo Camacho "Continuity" isn't a test. Continuity is a state of being - it means continuous. Continuity from one end of a wire to the other is good. Continuity of the positive conductor to ground is bad. Ghost voltage is not continuous - 0.0V is continuous. Continuity by itself isn't good or bad. It's all about what it continuous and when.
Hello Dan. I am a hobby mechanic and have been at it for decades. I purchased the Load Pro about 2 years ago along with the book. With the tool, book and your videos I have solved problems on modern day vehicles that at one time I could not imagine myself doing. Friends and family love me. Thanks for all you do. Merry Christmas and God Bless.
Really love this video as it fully explains the relay circuit. I have tried , unsucessfully until now, to understand this process. You explained and demonstrated it so clearly, as you do in all your videos. Gonna get my LoadPro leads out tomorrow and practice for a few hours. God bless and keep up the great videos.
All of the wire segments can be tested at the relay. Yes, loading 30/87 will see a drop, because that's the circuit with the load in it already. It helps to know what the relay is switching so you can predict what the "normal" drop will be. Most loads are pretty low resistance (Ω) You can always load the wires with voltage. Just look at the layout of the circuit and see what's where and devise your own tests.
The load in 30/87 is the solenoid, but if you simply read voltage at 30, you're testing only the pos half of the circuit. You could put the meter in 30/87 and load, but there's another resistor attached to 87. You'd have to know what the resistance of that load is to get an accurate answer. As you get more comfortable knowing what a circuit really is this makes a lot more sense.
Fantastic, I use your teat leads as much as possible. I need a little clarification on the relay terminal test. When you tested terminal 30 and found system voltage how did you test for voltage drop if the there was not a load on the circuit? You make great informative vids, the only complaint is, I would like to see more.
Hmmm.... Well, if you use the relay with the cover removed as in the other relay video, you'll immediately isolate it from one circuit to another - either the coil (85-86) or contacts (30-87). Once you've done that, you can test the two remaining circuit segments for what should be there. I'm obviously not a fan of the Powerprobe because of it's limitations, so you can't be sure you really, truly, have voltage at 30 - which is why I like the known-good working relay with the cover removed.
I'd be very surprised if the the clutch was that high of a resistance. 6.5Ω would seem more reasonable. However, if it *is* 65Ω, your math is correct. I'd test again to see if you read the clutch correctly. It takes a lot of HP to pull that clutch in, and lots of electrical HP is amps, and lots of amps need a *little* resistance - ohms. Remember - amps and ohms are ass-backwards. Nice job though!
Yes - that's correct, but be careful with the ohm value of the pump. Fuse size is a better clue. But, blowing the fuse in your meter is why it's there. Don't be afraid, but remember to start on the highest amp setting - usually 10A.
What an excellent video, practical, fast, efficient, and safe. Many of us don't have quick access to the exact wiring diagram and a method of quickly proving the wiring is extremely efficient. After a little thought I see why you didn't do the drop test on the negative side of the relay, because when you test at the relay connector the device is still in line. You expect to see a drop on the device side, based on the ratio of resistance in the 25 ohm LoadPro to the dynamic clutch resistance, which might be confusing to techs not paying attention. Since most relays are on the positive side of the device, the assumption is fairly secure and also partially verified when there is no drop on the 12V side. It's nice to know you aren't going to cause much harm until you get to the ammeter stage. I've fried a few cheap meters when current was higher than I guessed, ha ha.
So you couldn't use a meter to jumper (30-87) on a higher amp circuit such as a starter right? I think my DMM tops out at 20A. You would have to leave the relay in for that.
Thanks for the kind words and advice-i had to pat my self on the back after this one. The diagnostic took longer than the repair as you state in you book, it took me roughly about 30 minutes to diagnose, that includes getting a diagram, isolating the circuit, and testing. The repair took 10 minutes at most, soldering a new pigtail (2 wires) and a new resistor, and verifying the repair with the LoadPro. This time i had virtually no drop in voltage across 30/87, and the fan turned on...Success!!
Daniel Sullivan I under stand that you are checking out the relays which is very important. now can you please break it down for people by telling them how to set up the meter before they go to the prongs to get the reading. This would be for me an others that are not so experienced. Thanks
This video is a good test to see If I understand any of your videos. I don't . I failed the test. The circuit of the electric clutch must be switched on to do a voltage drop test . You did a voltage drop test when you loaded the LoadPro, I guess, I can not be sure of the meter reading because of the camera shot to the meter screen. I don't know from your explaination If you turned on the circuit, Or how you turned the circuit on, if you did turn it on . Not knowing if you turned the circuit on ,I have to guess you did , because you operated the Load Pro as one would if they preformed a voltage drop test by pressing the Load Pro button But how could you have turned the circuit on if you intended to get a correct Ohms reading , which requires you to isolate the relay and wire from the circuit At terminal 30 you got system voltage of 12.20 ......................... you loaded the circuit, got 12.11 What is that supposed to tell me? The voltage did drop but not enough to indicate the clutch is operational because it can't work on merely on a point o9 volts or .09 volts The second time you loaded terminal 30 you had a voltage drop from 12.26 to 12.19 volts Then you say " That confirms it goes all the way back to the battery At the4 min mark You say "I'm Ohming out the clutch from the relay" I think that means "You have isolated the clutch from the relay" No I have no idea what that means In your book and in other of your videos you say to read ohms .The devise must be on the bench removed from the circuitl .. Here The devise. The relay The wire The AC clutch all the way back to the battery.. A complete circuit , Through the positive side? That show continuity.. Everything is connected , the way it was designed. Is that right or not right? If right why would there be any ohms or resistance . I've read the definition of continuity till I'm blue in the face. Every thing is connected correctly as designed But apparently I still don't understand what it means How can a reading of 3.9 ohms indicate continuity? Is that because 3.9 is alot closer to 0 than to 1000 Ohms or 10,000 Ohms Is 3.9 consider no resistance? Would 50 Ohms be consider continuity or no resistance How much resistance or Ohm s would it take to show lack of or not continuity?
bob brawley if you read ohms you have continuity. whether that's 1k or 10000k you have it. a beep test would beep. a voltage drop is caused by how much resistance (in ohms) you have in that circuit. if you put in 12v & only get 11v out you have a complete circuit, but have significant voltage drop. can't pull ohms law out of the back of my brain right now , but look it up & that will help you understand cause of voltage drops.
bob brawley Good questions, I suppose for example if the Ohms in the circuit should exceed the ability of Amps to push the A/C blower motor then there's too much resistance either coming from a worn motor or the circuit having corrosion which is my guess why there will never be a Zero ohm reading. Of course we need an expert to clarify as I am just a DIYer. Its to my best guess if something is exceeding 100 ohms you'd have more heat in that circuit and therefore more likely to blow a fuse or in the case of a worn AC blower motor bearings greater resistance by the motor perhaps eventually creating more heat there and further breakdown until the motor stops altogether. I used my Amp clamp on the return side and got a reading of 30amps. I then proceeded to take my amp clamp to a new motor under load and read just a little above 13amps. Big difference especially when factoring in Ohms. When it comes to a transistor/resistor voltage where voltage drop is intentional I suppose that ohms must go up in reading and where there is resistance there will be heat but that's the intended job of a resistor.
If I could get Daniel Sullivan to clear up any misnomer I may have spread, does a worn motor across a live circuit increase resistance and therefore acting like a resistor and amperage will be higher and therefore proportional to the amount of resistance? As a question to Daniel is this why I'm reading 30amps plus from my amp clamp on the return end of a worn AC blower motor? Just curious and I have ordered the Load pro from Amazon to make life easier.
Informative video love the load pro however in my opinion relay schematic you have is incorrect, terminal 87 is referred as the load circuit in that on that circuit is our electrical load which is the coil for the AC clutch in this case the resistance reading you read includes the conductors, the electrical load and ground path back to battery and NOT a normally open circuit. Also terminal 30 of the relay is regarded as the voltage or power supply circuit of the relay switch. Other than those points I do appreciate your video
It is the normally open contacts, and hence the normally-open circuit. I really don't know how you're distinguishing between a semantic difference. Keep thinking, but I don't think you're quite on target here.
BASICALLY if the Meter is set on A and one lead is in 30 and you ping one of the low side sockets(85,86) which are wired to the PCM... fried computer! LOL
Love the videos Dan. I just purchased a load pro and your book. Hope to become good at troubleshooting vehicle electrical problems. You really know how to simplify some otherwise complex troubleshooting problems. Thanks for sharing the information you have with everyone. Really helpful information. Thanks again.
Wow, I don't know much about electricity and am just learning how to use a multimeter to test circuits on my car but this is great. Still lost but that's OK. Thanks for posting.
hi dan I want to understand if cross voltage is normal in a circuit, or not ? and what it is, thank u Dan , your videos and meter are the best .keep itup,
I'm down in jamaica, small island in the caribbean,i have a load pro for years but never used it until now. Have just started watching these videos, really great and now fully understand how the load pro works and many many other areas that may have been cloudy, keep it up.
Dan-how did you read amps across the load (30-87) without a jumper across the coil (85-86). Am I understanding this wrong. The fan clutch clicked but I didn't see how the circuit was completed with the relay removed.
Because the ammeter is a jumper across the relay switch - 30/87. The coil -85/86- is completely independent of the contacts. You can also use the relay with cover removed as in the other video.
Quick Question..Is it possible to find high resistance in the wiring by testing at the relay?... if you put your terminals across terminals 30 and 87 with the meter reading Volts- you're gonna read 12 volts but if you push the button on the Load Pro and the voltage drops then you have corrosion in the system correct?? Then you would move the (-)lead to a good ground and retest and find out if it's in the (-) or the (+)
my dashboard lights dont go off on my 1999 ford windstar... i went to an auto repair place and they tried to put a new dashboard and the auto theft came on.... when they take out fuse 10 or 16 the headlights stay on... i have to disconnect the battery each time i park because it drains my battery.... i dont know what it is?? module or electrical short?? HELP!! I want it fixed before winter
Gan I use my load pro for starter motor voltage drop test from the relay?My guess is not,because of high amperage.How about loading the starter cable disconnected from the motor and loading it with load pro button... would I see a drop If the cable is corroded ,or the load pro and DMM bias voltage is not strong enough? Thank you
Thanks for the quick reply MrSullivan. The reason for my question is a Ford Focus with a low speed fan circuit problem. The fan was not turning on when it was supposed to but the high speed fan worked just fine, tried commanding the low speed with a scan tool and i heard the relay clicking but no fan-so i tested with the Load Pro and when testing across 30/87 i had 12 volts, and 1.5 when loade-I found a burnt wire at the cooling fan resistor!.i even got a picture of it to show it off ;)
Hi there Mr. Sullivan: I understand how you used the Load Pro to measure if there was resistance in the circuit on the load side of the relay. But how to you check the solenoid side that had only a ground and an open circuit to see if their is a problem electrically on that side since it does not have a battery voltage to check with the Load Pro. How do you rule out that circuit. Thank you.
+Dog Food Dear Gravy Train - you find a solid B+ source and probe the ground, if needed. But - if there *is* a fault, you retest with the ground lead on a separate ground. Process of elimination. You always have *BOTH* probes in the connector to start.
Dan - I have a park lamp relay problem (they don't turn on). I don't hear the relay click when the lights are turned on. I get battery voltage on all 4 pins of the relay whether there is load applied or not. The input side of the relay should drop low when the switch is turned on right? Also, if I jumper the relay switch connection points, the lights do not turn on. Any advice what this indicates? Thanks for the great video.
I teach to carefully take the cover off of a similar relay (or that one) and put it in the offending relay socket. Squeeze the relay. If the lights (in your case) turn on, its not them -- or vice versa. As for the meter, turn the lights on and read the voltage at 85/86. Should be source V (12V). If you see ghost V it's open. I'd expect from 2-4Ω if you read the resistance at 87 to ground. 30 is usually 12V. Just remember - it's always something simple.
Daniel Sullivan "Just remember - it's always something simple." How right you are. I had the relay in the wrong position (off one row)!! I had pulled it out when diagnosing a starting problem (meant to pull the crank relay), and in my haste must have put it back wrong. Once I put it where it should be, the lights came on. Two weeks I've been working on this - aaaarrrrggggg!
Thanks a lot Dan ever since I started watching your videos I have really gotten good, I'm doing all my work to my cars and my buddies as well. Keep up with the great videos and I'll see you on the next one. Thanks a lot
Phillip Kang If you're asking about the LOADpro - yes. There's a chart in the tool manual that gives the resistances for each drop, and it works on both 5V and 8V systems. Not inputs - because there's no voltage to read on an input, unless you create an artificial test by isolating the wire.
