tach, fuel injector?

howie ll wrote: I'm beginning to wonder if you are capable of doing this. Asking me for a picture of inst panel removal, are you kidding? Install work 101! Most oriental cars use a printed circuit to distribute the electricity to the various gauges, warning lights etc. If it has a rev counter there will be 4 terminals at the rear, ign, ground, illumination and TACH. By the way wrapping wire round it won't do it, that's inductive follow any of these posts, remove insulation wrap your PURPLE / white wire round it, test. If it works solder and insulate. For YOUR purposes all of the above mentioned methods work and before Oldspark reams me yes it's AC from YOUR point of view. Set DMM to 20VAC, should read between 4-7 volts as you increase the revs.

Sorry that I dont understand what inst panel is. I dont know many shortening words. Now I got it , it is instrument panel? Thanks

oldspark wrote: Crankshaft sensors are often reluctors which put out an AC signal. Just rectify it.... etc. equate wrote: Is there AC output on fuel injector during cranking? AFAIK no injectors are AC - they are all DC. I was saying that unlike spark, injectors may change the number of times they fire per engine cycle (ie, per 2 revs). Hence you are probably better off sensing spark. And like spark, they might fire 1, 2, 3, 4 etc times per cycle.

So after start, is there stable AC on fuel injector when car is idle? thanks for sharing this. it is a class for me.

What is AC? There is no AC (as in AC voltage aka "Alternating Current Voltage" just to confuse other readers....) on fuel injectors.... If you mean a chopped DC signal as in on-off, yes, that exists. But maybe not a stable rate - that would depend on the system and I am not familiar with KIA, though I doubt it would change the number if injections pulses per cycle (it isn't a dedicated or high performance car...?).

Camshaft sensors won't always work because they don't always put out stable pulse trains.  Some of them have very funky keying on them that make signals that can't easily be understood by the remote start.  I remember physically seeing the cam sensor of a VW Jetta and thinking there was no way a remote start would ever learn the signal it was gnerating!

You would be best off finding a tach wire using a frequency meter - Sears sells a Craftsman meter that reads frequency for ~$25.

When setting the meter to AC you are basically trying to read a pulsing DC signal.  The AC setting doesn't do a very good job of this and unless you've done it several times you won't have a clue what you are looking at.

Kevin Pierson

I knew Peter was going to ream me out on this but you as well Kevin? I did say "for your purposes it's AC". It was easier than trying to explain, because of the poor lad's language barrier problems. Yes I did mean INSTRUMENT PANEL. The gauge I was referring to was the TACHOMETER also known as REV COUNTER.

Apols Howie - I didn't register that part of your reply (slack me....). I was tempted to reply that the only difference between equate's AC and our pulsed DC - which is AC with a DC offset - is a capacitor to remove the DC offset. The AC range of an AC meter usually has this - hence why reading the AC value for a DC signal works. But I didn't - having seen things from ~5 years ago like Tach and RPM?... (ie: confusion of IgCoil- waveforms (from points etc) and outputs from reluctor sensors, Halls or Optics, and Ignition Coils), ...I guess I was more focused on some other wisdom....

howie ll wrote: I'm beginning to wonder if you are capable of doing this....

We seem to concur that each signal source can vary or be unsuitable. The difference between AC & DC is trivial - eg, a series diode-and-capacitor. Probably the simplest universal signal is spark - usually even multisparking can be filtered out. With the specific timing info (from ECU, ignition, & CPS) the answer would be simple....

But a Duty Cycle has AC, so is it AC? Not that I'm arguing... I know I have had a firm idea of what is AC or not, but I can't recall what that was... Maybe it depended.... I remember my dad describing AC as "forward & backward" electricity (ie, probably current). Later I understood that as the classic +ve & -ve etc. Later still we converted to Arabic numerals. One could argue that DC is a purely fixed voltage with no ripple (frequency). As soon as it deviates, it has an AC component - viz: a square-wave is a series of (odd?) harmonics; the size of its DC offset determines whether it goes above/below the zero-Volt line. Any varying waveform can be represented by a summation of sinewaves (Fourier etc). Sinewaves are AC. So how is AC defined - a varying voltage, or a swing above/below the zero line? I can see AC merely as a changing voltage (ie alternating between 2 values, not 2 polarities). Transformers work on AC. You cannot transformer-transform DC, but you can if it switches between +6V & +12V - ie, an AC of 6V with a 9V DC offset) - but is +6V to +12V consdered DC? It all depends what you are considering, and in what context. An AC meter should accurately measure the AC voltage irrespective of whether it is +/-3V or +6 to +12V (ie, +9V +/-3V) - the capacitor removes the DC offset. But many forget that our DMMs etc are generally designed sinusodal waveforms (not square, or peaked etc) and maybe even for low (mains) frequencies. Mechanical meters were probably better for these mixed waves - they'd show an average DC value. DMMs however might give a reasonable AC reading, but on DC they will be all over the place depending in where they happened to sample.... Hence true-RMS DMMs etc. The important thing is to realise how this all impacts.... It's like confusing "power factor" with Cos-phi - the phase angle between AC current and voltage. That was rarely a problem until computers etc (SMPS) where CosΦ=1, but pf (power factor) is often 0.6. (Leading or lagging LOL!)    FYI: pf = W/VA; not CosΦ. But if it's sinusoid with no harmonics (distortion), then pf = CosΦ. To me, the fundumental practical difference between AC & DC is a DC-blocking capacitor. I find the "any voltage is AC with a DC offset" model very useful - whether the frequency (AC) is zero, or DC = 0. And yes for both current an voltage - ie AC & AV, and DC & DV. But anyone that argues that a speaker overheats because a half-AC cycle is DC.... Sorry - it doesn't work like that! (That's a referral I've made before to some ancient post on the12volt - very logical and plausible (to the lay-person?) but just totally wrong & void.

No - not at all. What I say is a fact.... albeit mathematical if one can't picture the waves.... The problem is the definitions. DC is usually considered unidirectional - ie, always +ve, or always negative. It is hence constant polarity that can thus vary its magnitide (value). But sometimes, DC is considered to be of constant magnitude. An example may be the 12V automotive system. This is often analysed as a constant DC voltage with superimposed AC signals. (This ignores the slow changes like discharge from 12.7 or charge-voltage adjustments.) Or how about a reluctor sensor with its AC voltage of (say) +/-3Vp-p (ie, 6V peak to peak)?... If it were referenced to 5V DC (ie, biased at +5V), it would only ever swing from +2V to +8V. Hence it's DC. But if it were GND referenced/biased, it is +/-3V and hence AC? Or - we all know you can't transform DC, and yet a 12V ignition coil works despite its primary always being DC (ignoring inductive reactions). IE - one end of its primary winding is permanently +12V or +8V etc. The other primary end is shorted to GND, else floating. It never goes negative. In fact it is usually slightly positive due to finite resistance hence voltage drop across the points or solid state switch. Hence it never changes polarity, and yet it transforms - we get an induced voltage out the secondary - but with a supply that was only ever DC (ie, on or off)? So therefore we can transform DC? No - we can only transform AC - its DC is a different issue. (EG - heating - as in speakers where only the changing (AC) voltage produces sound, any DC may cause overheating.) Whether or not an injector voltage/current is AC or DC depends on whatever definition - just like a reluctor, ignition coil, or noise on a +12V rail. But a fuel injector signal definitely has an AC component, as does any varying-magnitude "DC} voltage. As before.... Any repeating waveform can be represented by a summation of sinusoids - eg, square waves, triangular/sawtooth waves etc. (So can non-repetitive waveforms - otherwise digital sound recording wouldn't work, but lets KIS for now!) A square wave is a sum of many sinewaves. The only difference between a +/-6V squarewave and a 0V to +12V is a +6V DC offset - their AC content are identical. So - I am not being difficult - I am merely describing reality. It's the reality that is difficult!! [ Reality?? Ha! I have just discussed what is essentially a mathematical underpining of our electrical theory. Some think the maths is not real - but the maths is the only thing real about it - electricity is not "real" as far as many comprehend - but many understand its effects, how to use it and how to design it etc. The maths is as real as Ohm's Law - it's only unreal when Ohm's Law doesn't apply. But I can assure you, the effects of electricity certainly feel real - especially when more than 100mA through a 2k-Ohm impedance! ]