wait a minute George. A car alternator generates A/C current. Before the current is delivered to the battery, it is converted to D/C (corrected my spelling from A/C) current by a rectifier inside the alternator. How can there be A/C current anywhere else in the cars electrical system.
A capacitor does not 'block" A/C current. It is a component that temporarily stores energy (electricity) and discharges it on demand.
I do agree that if your volt meter is switched to A/C and you measure a D/C voltage that you may see a value displayed, but not necessarily an accurate one.
I think you have a typo above, I presume you mean âit is converted to DC by a rectifierâ.
Which is correct.
A/C maybe is a little bit of an ambiguous term. I guess technically it means âalternating currentâ which is current that goes one direction for a while (like from positive to negative), then reverses direction and goes the other way (like from negative to positive). If thatâs your defân of âACâ, then you are correct. For the most part current only goes one direction in any of the carâs circuits, from positive to negative.
But scientists and engineers often refer to AC as any voltage or current mode that isnât pure DC. Pure DC means the current goes only in one direction, and holds to a steady value. For any circuit theyâd say thereâs an AC component, and a DC component. So like for an alternator theyâd measure the âAC componentâ of the alternator output using a voltage meter set to AC. When the meter is set to AC, it ignore the DC component, and only measures the AC part. How accurate a measurement it is depends on the meter. You are right that often it is only an approximation, esp for less expensive meters.
Try the experiment I mentioned though. I think youâll measure â even w/an inexpensive meter â an AC component on the fuel injector solenoid circuit when the engine is running, and no AC component when it isnât. Let us know what you discover.
Edit: Capacitor blocks DC? If interested, read here
How does a capacitor block DC?
got the car running today after replacing the water pump timing belt and tensioner. after making sure the cams and crank were timed properly. when it started the engine sounded like the valves were ratling it has a zero tolerance engine was curious as to what that could be causing the noise
Congrats on sticking w/it and getting your CRV running again. Like dB says above, rattling in the valve area is often due to the valve clearance set too high. Too high is better than too low, so if it is off, your way is the better of the two. Too high however can cause some loss of power, since the valves wonât be opening as widely as they should.
Itâs curious that a water pump and timing belt job turned a non-running engine into a running one. That usually wouldnât be the case unless
the old water pump was binding and loading the engine (unlikely)
the old timing belt was not aligned properly (which would be easy to check when removing it)
So was the old timing beltâs alignment checked before it was removed?
Did you do a compression check as part of all this?
after adjusting the valves 15 of the 16 were out it purred like a kitten then died again last night with the oil light on i now believe the oil pump is malfunctioning causing a cam to bind temporarily and making the timing jump witch it did again
Does you car use a distributor? If so, might want to ask your mechanic to pull it out of the engine and check to make sure it hasnât been damaged. I say this b/c oil pumps are a very uncommon failure item. B/c they are constantly bathed in oil. When they stop working it is often b/c they arenât getting their input power drive for some reason.
hmmm ⊠well, if the engine hasnât ever been rebuilt in 300 K miles, given the troubles you are reporting, might be time to give that option a think. It may be faster just to to take it apart and replace all the worn parts. And in doing that youâll likely find whatâs causing these problems, and be able to easily fix them during the rebuild, and wonât have to guess any more. Plus youâll wind up with a like-new engine.
i donât know what had been done to it in the past as we just purchased the car but have very limited money so cant do a complete rebuild the man we bought it from did replace the rear end, plugs and wires, brakes and a few other things
I donât want to butt into this but is it possible that it has a fuel pump shut off when the oil pressure gets too low? My Rivieras had that. So it runs until the low oil pressure light comes on and then stalls? Or does it stall and then the oil light comes on which would be normal. Or it stalls because it jumps a tooth because of low oil pressure? Just trying to understand the sequence. Suppose you could pull the oil pan and put new bearings in or at least inspect them to see how bad they are. Donât know if that would resolve the low oil pressure issue but used to be done a lot.
Db4690 is correct; a worn out engine. Thatâs not unheard of at 310k miles. I hope you did not pay someone more than a few hundred bucks for that car.
You can drop the pan, remove a few rod and main bearing caps, and inspect the bearing shells. Odds are you will see nothing but scored copper; meaning theyâre gone.
Whether new bearing inserts help at all or for how long they may help is a huge unknown. That would depend upon how worn the crank journals are.
Iâm guessing if those bearings you mentioned are gone . . . that wonât be the only worn out parts in the engine, as far as oil flow, pressure and lubrication go