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#16
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Micalk,
Thanks for the logical and detailed discussion. One other question for you... My voltage regulator failed, replaced it, and the alternator works... But before the Bosch 14V regulator failed, I was getting 13.5-7V or so max unloaded at idle. I put in a beru 14.2V regulator, and still get 13.5-7V at idle. My battery was flat after the regulator failed, but I charged it fully and then let it float. So it isn't an issue of high load for recharge pulling voltage down. The higher voltage regulator trick worked on my 91 BMW when I put a hella 14.1V regulator in place of the Bosch 14V regulator - the bus voltage was better and the battery topped up better. Basics are solid, all connections are super-clean and tight. I was wondering if you had any thoughts... Also, I was thinking that it might be beneficial to ground the battery to the alternator body via a small line attached to the battery cable. All the chassis grounds, like the engine ground strap are clean and tight. Any thoughts? Thanks!
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Current Diesels: 1981 240D (73K) 1982 300CD (169k) 1985 190D (169k) 1991 350SD (113k) 1991 350SD (206k) 1991 300D (228k) 1993 300SD (291k) 1993 300D 2.5T (338k) 1996 Dodge Ram CTD (442k) 1996 Dodge Ram CTD (265k) Past Diesels: 1983 300D (228K) 1985 300D (233K) |
#17
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I'm good with wiring and circuits, and I know how an alternator works, but I don't have alot of real-world experience with these alternators to be able to express well-founded opinions. But my understanding is that the 55A alternator just doesn't put out enough voltage at idle. A simple regulator can't bring up voltage where it isn't present.
You actually have some load at idle - you are charging the battery after starting it at the very least, plus your gauges, some of the AC circuits are energized when the Climate Control Unit is off, same with the cruise control. And I'd think you'd actually want some minimum load in order for the regulator to perform correctly. Check to see what happens to the voltage when you rev your engine. Turn on the lights or the ventilation blower motor just so that there's a bit more of a load to push . If you know what voltage your old regulator would peak at under these conditions, then you can tell if there's a difference with the new regulator. I was actually just a bit surprised when I got my AL129X. It had the same regulator (had the same part number) as the one in my 55A Bosch alternator. As I said in an earlier post, the AL129X will put out higher voltage at idle which may be, in part, what you are looking for. And don't bother asking me what I think about the new alternator. I smushed up my front end last year, and I installed it while I had the front clip disassembled. Liesl is in the shop now getting repaired and painted finally, so I'll soon be able to enjoy her again. If all your connections are tight, then you shouldn't need a wire to the alternator body. You can try this test to see where you stand, though. Load the alternator as much as possible - rear window defrost, low beams and fogs, brakes, AC blower going full, stereo blasting, etc., to get as much current flowing as possible. Set your voltmeter to the lowest range of DC voltage (you may not be able to choose, but that's okay). Then measure from the body of the alternator to the engine block, and from the engine block to chassis, and from the chassis to the negative battery post. Any voltage drop would indicate a less than optimum connection. I know that multiple ground paths are bad ideas for electronics, not sure how it would affect a W123. It probably wouldn't. Would probably be worse on a more modern "electronic" vehicle. And I don't know how much you'd gain by adding a wire, or how big it should be - those kinds of answers require engineering analysis with more information. But I'd expect that you won't find much if any voltage drop if as you say all your connections are clean and tight. And this would indicate that you'd derive no benefit from an additional wire from the negative post of the battery to the alternator body.
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mjk '84 300SD 119KMi (Liesl der Diesel) '84 300D 326KMi when the oil left (former parts car) '82 300SD 253KMi (new parts car) |
#18
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Here's some back ground might clarify things:
A neat analogy to help understand these terms is a system of plumbing pipes. The voltage is equivalent to the water pressure, the current (amps) is equivalent to the flow rate, and the resistance is like the pipe size. I=V/R Let's see how this relation applies to the plumbing system. Let's say you have a tank of pressurized water connected to a hose that you are using to water the garden. What happens if you increase the pressure in the tank? You probably can guess that this makes more water come out of the hose. The same is true of an electrical system: Increasing the voltage will make more current flow. Let's say you increase the diameter of the hose and all of the fittings to the tank. You probably guessed that this also makes more water come out of the hose. This is like decreasing the resistance in an electrical system, which increases the current flow. Electrical power is measured in watts. In an electrical system power (P) is equal to the voltage multiplied by the current. P(Watts)=Volts*I(Amps) The water analogy still applies. Take a hose and point it at a waterwheel like the ones that were used to turn grinding stones in watermills. You can increase the power generated by the waterwheel in two ways. If you increase the pressure of the water coming out of the hose, it hits the waterwheel with a lot more force and the wheel turns faster, generating more power. If you increase the flow rate, the waterwheel turns faster because of the weight of the extra water hitting it. Cut and Pasted From: http://science.howstuffworks.com/environmental/energy/question501.htm For that sake of arguements: 12 Volts X 55 Amps = 660 Watts 12 Volts X 80 Amps = 960 Watts More Watts can run more stuff. We know there are fixed values that we cannot change or we have to change to resolve the problem. The size of the an alternator (output in Amps) is a fixed value. It's rated for a certain amount. We have to increase the value to increase the total system out put. Voltage is fixed. Our systems are designed for a fixed amount of Voltage (the force in the reservoir (battery)) We normally say 12 Volts, but in actually its 12.6 Volts. To provide a proper charge we need 13.8 to 14.4 V (Volts) One of the things that does change is system resistance. As contacts/connections get older they don't flow as originally designed and it increases the resistance. Which decreases system efficiency or lowers the watts available to drive other devices. This is pretty basic. But hopefully you get the overall picture.
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92 300D 2.5L OM602 OBK #59 |
#19
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My point of disagreement with what is stated above is that higher voltage will not cause more current to flow in a system like ours. Higher voltage will result in less current required for a given load.
__________________
Current Diesels: 1981 240D (73K) 1982 300CD (169k) 1985 190D (169k) 1991 350SD (113k) 1991 350SD (206k) 1991 300D (228k) 1993 300SD (291k) 1993 300D 2.5T (338k) 1996 Dodge Ram CTD (442k) 1996 Dodge Ram CTD (265k) Past Diesels: 1983 300D (228K) 1985 300D (233K) |
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