mjb59
Rover Fanatic
Posts: 311
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Post by mjb59 on Oct 20, 2018 0:31:23 GMT
Ok, I've looked at lots of youtube clips, and am learning how to use a multimeter, but can't find what I'm looking for and wondered if anyone can help.
My indicators/flashers slow down a lot at idle, and increase as revs increase. I'm also learning to look for a parasitic drain, with help from Enigmas link to Eric the car guy clip.
Enigmas suggested the variable flasher rate may be either bulbs of different voltage, or maybe bad grounding on the flasher light circuit. I've just checked all the globes, and the festoon flasher lights from the side of the car are 12v 3 W. and the front and rear flasher bulbs 12v 21W.
I'm laying my ignorance out for all to see here: Where do I put the multimeter leads to check for a good ground on each circuit? Many of the youtube clips have the battery in the engine bay and use the battery as a reference point for one of the leads. Some of the clips showed a device you are all probably familiar with but I'm not - a lead to the multimeter with a needle thing in it that penetrates the wire on the relevant circuit to test that wire.
So, firstly, the battery is in the back. And secondly, where do I put the multimeter leads to check for a good ground on any particular circuit? And what is an acceptable impedance ie. what number of ohms suggests the ground is good and what number bad?
Honest, I have tried to research this myself before troubling you! And the Eric the car guy clips are great!
Thanks.
Michael.
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Post by Phil Nottingham on Oct 20, 2018 5:41:39 GMT
You need to put one probe on the side of the bulb (which must be clean) and the other on the bodywork a bare metal area/earthing point or the engine with the range set at its highest (ie Megaohms) at the beginning and moving down till a reading shows and then compare the reading to doing it with the battery earth cable to the bodywork. They should be the same and a very very low or at ZERO.
Even this will not always prove a good connection in service as it needs a much higher test current through it which that sort of meter just will not provide.
A far better way is to just connect a light jumper lead from the lamp body or side of the bulb to the (good) earth point on the body when the lamp is on. If it speeds up or becomes brighter then it's a bad earth.
Bad connections in the entire circuit (and there are many) will cause the mechanical flasher can to slow down as a can a faulty one or even the switch contacts. Direct jumper leads are an easy way to test these as they bypass the bad circuit in whole or in part depending on how and where they are connected. There are numerous hidden bullet connections which when located behind the trim (eg A panel) look OK but when pulled either fall apart or are full of verdigris
Clean everything and try a different flasher can - they are cheap! An electronic one which needs an earth of its own is less bothersome. Electronic ones will need the telltales wiring modified slightly to work properly. All this is on search. Some electronic ones will not work on positive earth systems however
Its all about being methodical and a process of elimination and understanding what the circuit is (P5 wring is very basic) and the same process is used for parasitic drains which can be found very quickly without meters but one can be used on a low volt setting or better still amps
BTW its normal for them to slow down a little at idle with dynamo systems but a current drain or regulator fault eg sticking cut out points will cause a heavier discharge which causes a bigger volt drop. You can connect the 3 flasher connections together to allow the one side indicators to stay on constant and test the voltage which should be almost identical to the direct battery voltage across its terminals with and without engine running (fast idle)
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Post by enigmas on Oct 20, 2018 14:23:48 GMT
Michael all your ground/earth connections on the body of your car must be to bright clean metal. If they're not you'll have high resistances and electrical issues.
First set you multimeter to the lowest ohms scale. Mine has a 200 ohms setting and incorporates a buzzer. Now touch both probes together (the red and the black). My meter reads .4 ohms. This is the resistance within the meter. So if I was measuring a component that showed say 10 ohms resistance...I'd need to subtract .4 to arrive at the actual resistance of 9.6 ohms.
But you need not concern yourself with this unless you're measuring electrical components that need to be within specific parameters.
All you're currentlly trying to do is ensure good 'earths' to switches, bulbs and other components.
Ensure that the main battery earth lead in the boot is properly grounded to the car body, i.e., to bare, clean metal. Do not be precious about paint work with earth connections. Use your multimeter on the lowest ohms scale by placing a probe on the battery neg terminal and the other probe on bare steel anywhere in the boot area. The reading on the meter should be very close to the same reading as touching both leads together. If it's not, then you've got a dirty connection at the battery or the body.
Similarly, the ground connection from the engine bay to the engine block needs tp be checked.
As for the various lights...indicators, parkers, stop and headlights...if there's an earth to these, disconnect the positive battery lead first, hold one probe against the body (bare, clean metal) and touch the other to the wire at the bulb connector you believe is a ground. If it's a ground wire your meter will either buzz or show a low ohms reading as previously mentioned. Remember, that the side of the bulb and the bulb retainer are all part of the circuit and need to be clean!
Once you've verified that the earths are all good, you'll also need to verify that each electrical device gets 12v. So now reconnect the positive Battery terminal and switch the meter to DC volts...usually 20v. And check the power supply wires.
If you can't get access to a wire within a plug, push a small sewing pin through the plastic insulator of the wire and check it like that.
Also check the car's output voltage to the battery with the engine running. Use the 20v DC scale and place the appropriate leads on the appropriate terminals. You should see around 14.5v or perhaps up to 15v with a generator if you rev it a bit.
Hope this assists.
PS. My reference to you initially Michael about mixed bulbs had to do with 'Watts' not volts. All indicator bulbs need to be of the same wattage.
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Post by lagain on Oct 20, 2018 18:55:51 GMT
I have an electronic flasher unit on my car and the flash is always the same regardless of revs. I have posted the details on the forum a couple of times, but I cannot find it on search, infact I can never find anything on search !
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mjb59
Rover Fanatic
Posts: 311
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Post by mjb59 on Oct 20, 2018 20:32:32 GMT
Phil and Engimas thank you so much for your advice and assistance! The youtube clips are great but often have just enough assumed knowledge that some key basic is missing for the absolute novice.
I am humbly aware that the information flow on this forum is always from your positive to my ground, but your efforts are greatly appreciated.
And lagain I did find on search the entry about the electronic flasher and the need to add a ground to it, and the fact that the original flasher unit does tend to slow with revs.
I advance towards the car with multimeter and new confidence and will report back. A week ago I'd never heard the term parasitic drain and I'm looking forward to finding the ghost in the machine.
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Post by djm16 on Oct 22, 2018 2:17:48 GMT
"My indicators slow down a idle".
This happens if you have an older style mechanical flasher can. This works by a coil of nichrome wire heating up a bimetallic strip which then breaks the circuit until I cools down. The flashing rate is quite voltage sensitive as the heating rate is voltage sensitive. This in itself is not a disorder.
The reason your indicators are slower a idle than at speed is because the voltage at the can is lower at idle than at speed. Whether this is a problem or not depends on how big the difference is.
You may have a problem IF:
1) Your car has an alternator. The alternator should be pushing out the same 14.1V at idle as at speed.
OR
2) You have a generator and your battery is bad, so that the battery, minimally loaded, is only putting out 10V or less, while the generator at speed is putting out 15V (which would be correct).
OR
3) Unlikely, your battery is fine and is putting out more than 12V, minimally loaded, but your regulator is maladjusted and allowing through 18V instead of 15V at speed.
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mjb59
Rover Fanatic
Posts: 311
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Post by mjb59 on Oct 22, 2018 6:16:41 GMT
Thanks djm16. I'm slowly finding my way around the multimeter.
I have a new battery. Voltage b/w posts = 12.35. Voltage at idle about 13.9v. Voltage at 2000 RPM about 14.1v and doesn't rise further with increased revs. I was worried it might have been overcharging as the battery I've just replaced was very bulging. So I presume this means the alternator is essentially ok?
I started looking for a parasitic draw, as my batteries have been dying quickly. I removed the ground lead from the battery, and with the meter leads between the ground lead and the negative post of the battery, engine off, doors shut, everything off, it was drawing about 5 milliamps, which from my research would seem low, and may be due to the clock?
I bought a new toy which you may be aware of, a bluetooth connection to the battery that gives a readout to your phone of the battery health. I thought this would keep an eye on any significant parasitic draw. So far after a couple of days, still charged at 98%. Maybe I've just had bad luck with batteries? The battery guy says some batteries are now coming with this bluetooth technology inbuilt.
Re. the variable flasher speed, thank you for the explanation. I'm prepared to wear it now I know it's not necessarily pathological.
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Post by Eric R on Oct 22, 2018 6:54:58 GMT
slightly to one side ........ I have a battery monitor running 24/7 in a closed garage - the boot is left open. I have noticed a strong obnoxious smell. Could it be that the charging of the battery generates heat or fumes in these circumstances?
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Post by enigmas on Oct 22, 2018 8:18:48 GMT
slightly to one side ........ I have a battery monitor running 24/7 in a closed garage - the boot is left open. I have noticed a strong obnoxious smell. Could it be that the charging of the battery generates heat or fumes in these circumstances? Eric ensure the garage is well vented if you are charging the battery continuously. Ideally if you want to maintain a permanent state of battery charge purchase a modern trickle charger with in built circuitry that reads/maintains a safe charge and switches itself into sleep mode if required. Older style battery chargers will keep charging no matter the charged state of the battery. They will boil the battery solution (sulphuric acid) and in the process give off hydrogen. That's a 'kaboom' situation in a closed environment if there's an ignition source!
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Post by Eric R on Oct 22, 2018 11:34:08 GMT
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Post by Warwick on Oct 22, 2018 12:03:36 GMT
slightly to one side ........ I have a battery monitor running 24/7 in a closed garage - the boot is left open. I have noticed a strong obnoxious smell. Could it be that the charging of the battery generates heat or fumes in these circumstances? Eric, can you describe the obnoxious smell?
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Post by enigmas on Oct 22, 2018 12:16:00 GMT
It looks like a good choice to me...are you certain there are no small animals nesting in the garage?
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Post by Eric R on Oct 22, 2018 13:51:25 GMT
Best described as a gaseous smell. Gas engineers visited because I thought it might be a gas leak in the house but exhaustive tests failed to find a source. On leaving the engineer even took readings outside the bottom of the garage door but found nothing. It reminded me to open the door to show the Rover and the smell was strongest there once inside. As Enigma suggests when main and personal doors are left open for a time it clears. I have no ventilation other than the doors and no sign or vermin or other wildlife. I guess I could fit one or two air-vents into the soffits at each end. The battery itself remains connected but doesn't show any signs of distress and surprisingly the Rover starts on the button!
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Post by Warwick on Oct 23, 2018 6:04:33 GMT
Thanks Eric. Could it be a rotten egg smell? All that should be released by a charging lead-acid battery under normal circumstances, is hydrogen and oxygen. Both of which are odourless. Incidentally, this is why you need to top up an open vented battery with water from time to time. One of the effects of charging is to break the H2O water molecules into their constituent H2 and O2 parts. So water is lost from the sulphuric acid solution that is the electrolyte. (Sealed batteries have a catalyst at the top of each cell which generally manages to cause the H2 and O2 molecules to recombine into H2O molecules). When an open-vented flooded lead-acid battery (the traditional car battery) is charged and the oxygen and hydrogen gases escape, they can carry with them a small amount of acid vapour/mist, but that shouldn't be enough to be a noticeable smell in a largish room. However, if a battery is vigorously over-charged and it is not in good condition and beginning to fail internally, hydrogen sulphide (rotten egg gas) can be produced. And you don't need much of that for it to be noticed. But this is rare. I've only encountered it once, and it wasn't a car battery, and complete failure of the battery resulted.
If a sealed battery is overcharged and hydrogen and oxygen escapes from the relief valves without being recombined into water by the catalyst, the battery is finished because you can't replace the lost water.
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Post by Eric R on Oct 23, 2018 9:34:48 GMT
thanks Warwick. I have three sealed Bosch batteries all less than 3 years old.
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Post by Warwick on Oct 23, 2018 10:21:39 GMT
In that case, I can't see how the smell can be associated with the battery charging.
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