| Author | Message | ||
| Darrell Black, DVM (Darrelldvm)
Registered Member Username: Darrelldvm Post Number: 53 Registered: 6-2005 Posted From: 72.4.181.208 Rating: N/A |
The DC output post on my generator (4106) was leaking oil so I went to put in new insulating sleeves and O rings. The nut would not budge. I finally decided to sacrifice the DC bolt & grab the theads with the vice grips & get the nut off. Did not work, the bolt rotated & ripped the rectifyer wires off the DC bolt. So I cut the bolt, removed the end plate, replaced the rectifers, installed new DC output bolt, reassembled & VOLA..non-operationl! So, in testing I found that I have no 12V to the generator from the battery. (actually, from a Vanner Batt. isolator) Questions: Should the central lug on the isolator have 12v? Will the generator function W\O 12V input at the DC output post? Where do I start testing to find out where the problem is? The manual says to use an ammeter with 1.5V drycell battery??? Any suggestions will be appreciated. Darrell | ||
| Sean Welsh (Sean)
Registered Member Username: Sean Post Number: 1033 Registered: 1-2003 Posted From: 72.171.0.145  Rating: N/A |
Darrell, If by "isolator" you mean a device with two high-power diodes designed to "split" the output of the alternator between two battery banks, then, no, there will not be any voltage on the center (alternator) post unless the alternator is running. The whole point of the isolator is to keep voltage from feeding backwards to the center post from the batteries. Yes, the alternator should produce output without any voltage input. However, it does this by use of "residual magnetism." In some cases, you will have to "flash the field" in order to get this to work properly. The DN50 service and test manual for your unit is available as a PDF download from Delco. You should get the proper version of that publication for your model and use it as a starting point for further testing: http://www.delcoremy.com/Manuals.aspx -Sean http://OurOdyssey.BlogSpot.com | ||
| Darrell Black, DVM (Darrelldvm)
Registered Member Username: Darrelldvm Post Number: 54 Registered: 6-2005 Posted From: 72.4.181.208 Rating: N/A |
Yes, that is what I mean by isolator. I have the Delco service manuals, they are not helping. I need to know whether the rectifyer (diode) is a positve or negative (delco # 1894867) Diode symbol has arrow pointing to output wires. I may have put in the wrong diodes Darrell | ||
| George M. Todd (George_todd)
Registered Member Username: George_todd Post Number: 965 Registered: 8-2006 Posted From: 99.172.180.138 Rating: N/A |
Darrell, We need to clarify a couple of things here. 1. The alternator will not produce power without excitation, (the term for field current sent to the alternator from the voltage regulator.) So, with the master switch on, you must have 12V on the reg terminal, or you won't get output with the engine running. 2. As Sean very correctly says, "...the whole point of the isolator is to keep the current from flowing backwards..." So, if yours is what I think it is, you should have installed 3 of each of two types of diodes, in "pairs" on the three circuits. If they were installed in reverse, without an isolator, the diode wires would all have disappeared in a flash when you connected the battery. I don't know what will (or won't) happen with an isolator in the circuit, and improperly installed diodes, other than it will prevent a catastrophic failure. Does this help? G | ||
| Tom Caffrey (Pvcces)
Registered Member Username: Pvcces Post Number: 1322 Registered: 5-2001 Posted From: 65.74.65.93 Rating: N/A |
Sean, I don't think that the DN50 makes use of residual magnetism, at least, not in our coach. When the generator light is on, there is a circuit that passes a small amount of current to the field. This current is too low to start the alternator producing power at an idle, so we have to rev up the engine to get it to start. After the generator light goes out, that small current is eliminated because the source of the current is at the same voltage as the load. Without the exciter current, I don't think that the alternator would start up. For what it's worth. Tom Caffrey PD4106-2576 Suncatcher Ketchikan, Alaska | ||
| Bruce Henderson (Oonrahnjay)
Registered Member Username: Oonrahnjay Post Number: 533 Registered: 8-2004 Posted From: 149.168.204.4  Rating: N/A |
Hey, guys! Help an old grey haired guy who's easily confused out here. Are we talking about an alternator or a generator????? | ||
| Bill Holstein (Billmoocow)
Registered Member Username: Billmoocow Post Number: 61 Registered: 5-2009 Posted From: 98.232.207.25  Rating: N/A |
Darrell, Did this solve the problem or add to the confussion? Didnt see a reply. Work now? | ||
| Sean Welsh (Sean)
Registered Member Username: Sean Post Number: 1036 Registered: 1-2003 Posted From: 67.142.130.32 Rating: |
Tom, I can assure you that there is indeed some residual magnetism captured in the frame, and, like most brushless alternators, that magnetism could be used to start the unit, but of course, the regulator would have to be set up to do so. On my own coach I have a negative-side regulator; the F1 terminal is connected directly to the alternator output post with a short jumper. Today that output post also happens to be connected directly to battery positive, but when I got the bus, there was a big honking isolator connected to that post -- no possible way for battery voltage to get back to the field windings. All of the field voltage had to come off the alternator itself. If I had had an air-starter, I could have run the bus with no batteries at all. The DN50 is, of course, an externally regulated alternator, and the regulator would be on the battery side of the isolator, so the absence of battery voltage on the output terminal, per se, is of no consequence whatsoever. The output terminal is just that -- output, and there is no internal connection from there to the field windings. George's point, though, is well-taken: there does, indeed, need to be a source of +12v to the field. I confess I do not know whether the 4106 uses a P or N regulator; if it is the positive type, then the regulator should be providing something close to +12v on one field terminal, and the other (if present) would be grounded. In this case, the whole residual magnetism issue is irrelevant (as it is on your MCI). If it is the other style, like mine, then there is a good chance that the +12v is provided directly from the output terminal rather than from somewhere else, and, in this case, getting the unit going will depend entirely on residual magnetism. Hope that clarifies my response. -Sean http://OurOdyssey.BlogSpot.com | ||
| Sean Welsh (Sean)
Registered Member Username: Sean Post Number: 1037 Registered: 1-2003 Posted From: 67.142.130.32 Rating: N/A |
Bruce, Delco-Remy calls the 50DN a "generator", though most people would call it an alternator. Functionally there is no difference between the two terms. But we are talking about a device bolted to the main engine to generate DC power, not a separate engine-driven device to make house power. Now that I am thinking about it, though, I am realizing that Darrell's 4106 must have been equipped with the original 1960's-era 500-Type Delcotron Generator, which, IIRC, has only one field terminal and the other side of the field is grounded internally. So my comments in my last post about negative-side regulation, while accurate, do not apply to his coach. So, Darrell, ignore that whole discussion, and make sure there is voltage at the field terminal; you won't get any output without it. Test the diodes according to the procedure on page 2 of publication 1G-256, which should apply to your model. That will tell you if the diodes are good or if they are fried. It is not possible to install the diodes "backwards." However, I believe that Delco made both positive and negative ground versions of this model, and you'd better have the correct diode packs for the version you have. Once you have verified the diodes are good using the above procedure, you can verify you have the right ones as follows: Get a lantern battery (1.5v or 6v are fine). Using a clip test lead, connect the positive battery terminal (for negative-ground coaches; use the negative terminal if you have positive ground) to the heat-sink side of the diode. Now connect one lead of your voltmeter to the diode's output lead, and the other lead of the voltmeter to the unused battery terminal. If you read voltage, you have the correct diode. HTH, -Sean http://OurOdyssey.BlogSpot.com | ||
| Tom Caffrey (Pvcces)
Registered Member Username: Pvcces Post Number: 1323 Registered: 5-2001 Posted From: 65.74.69.12 Rating: N/A |
Sean, thanks for the explanation. I will try to be careful of the possibility that the alternator might self start when I am working around it. I was aware that some alternators had a small amount of permanent magnetism built right into the field, but I didn't think that the DN50 used anything but exciter current. Tom Caffrey | ||
| Darrell Black, DVM (Darrelldvm)
Registered Member Username: Darrelldvm Post Number: 55 Registered: 6-2005 Posted From: 72.4.181.208 Rating: N/A |
Thanks for all the info, but things have progressed. I re-removed the rectifyer cover to check just exactly what type of diodes were sold to me by Bus Service Inc out of Kansas. They were POSITVE diodes my 50dn uses NEGATIVE. So, they were backwards as far as current flow. New question: Has any damage been done by having 3 positive & 3 negative diodes in the unit? I ran the engine & I made sure I had 12V at the DC output post. I'll get new negative diodes ASAP Darrell | ||
| Sean Welsh (Sean)
Registered Member Username: Sean Post Number: 1039 Registered: 1-2003 Posted From: 67.142.130.47 Rating: N/A |
Darrell, If all the diodes were backwards, you would have basically reversed the polarity of the generator, and you'd have sent +12v through your frame ground with -12v on the hot side. Since you have an isolator, though, that would have effectively stopped any current from flowing out of the alternator in this direction. If either the "upper" half or "lower" half of the diodes are wrong, then the alternator will simply produce no output at all. If a single diode pair was reversed completely, you would have effectively an internal stator short in the alternator, which I would imagine would have made itself known almost immediately. I am guessing you had either the upper or lower half wrong, and no damage was done. -Sean http://OurOdyssey.BlogSpot.com | ||
| Darrell Black, DVM (Darrelldvm)
Registered Member Username: Darrelldvm Post Number: 56 Registered: 6-2005 Posted From: 72.4.181.208 Rating: N/A |
Sean, Thanks for the help, I'm going to talk to Delco tomorrow & get the correct diode, put them in & I'll let you know. Darrell |
