Regulated Voltage/Amp check

[tkhelm]

I'm trying to do the Regulated Voltage/Amp check, 17-4 in the Honda Service manual. After I pull the main 30amp fuse I connect the ammeter (multimeter) as shown and then start the engine. Except that without the fuse there are no electrics so the engine won't start.

Am I right that the multimeter is supposed to be making the connection in place of the fuse? If so, I must be making contact at the wrong points and not getting a connection. In the diagram it looks like the red multimeter probe goes to the red wire in the starter relay switch connector and the black probe goes to the right-hand bolt-like thingy under the rubber cover behind the 30amp fuse. Am I touching the wrong points?

Also, the Note says I should first turn off the lights and other electrical equipment. Am I correct in interpreting this as pulling all the fuses in the two fuse boxes to the right of the battery?

 

[John OoSTerhuis]

If you've pulled the ignition circuit fuse, put it back in.

Two fuse boxes?

Why are you performing these checks... what's the problem/symptoms?

Regards, John

 

[tkhelm]

John, the second fuse box is for ABS/TCS stuff. Good point about keeping the ignition fuse in. Actually, I hadn't taken any of them out yet as I was first trying to make sure I could get any reading--I couldn't because with the main fuse out (but all the others in) I had no life from the starter button. Setting that aside for the moment for your bigger question: why am I performing these checks?

A while back my ST died on me a handful of times while riding, in each case after long periods of time at low revs. Dead battery, but things came back to life when I charged the battery and all seemed to be OK until the next time, and until the battery itself finally tested out as shot. At that point I installed a new battery and a voltmeter. I was able to see that I was getting juice from the alternator but in decreasing amounts as I rode at in traffic / low revs. It would start out showing about 14.8V but drift to below 12.0V during the course of a ride, sometimes within 30-60 mins.

The diagnosis from my local STealer was that both alternator and VRR needed replacement. The $1800+ estimate made me to decide to become a DIY'er and dig into this myself. In the course of re-doing the diagnostic steps prior to committing to major alternator surgery, I discovered that simply applying electronic cleaner to all the connections solved the problem. I was back to 14.8V with the engine on. On a related note, I discovered that my idle speed was supposed to be set at 1200, not the 800 that it had been at. Between those two things I thought I had solved my $1800 problem for about $10, and had learned a few things in the process.

Unfortunately, a few weeks later the voltmeter started showing little to no charging at all--worse than before. Once off the battery tender and out of the garage it goes down from 12.8 to 12.0 over the course of a short ride with no indication that the alternator is kicking in. Problem not solved after all... My question above was prompted by my attempt to follow the diagnostic steps in the Honda Service Manual. Inspecting the regulated voltage is the second step, after finding that battery current leakage is normal.

 

[tkhelm]

I have since done the steps that you recommended in this other thread in post #3:

1) Each of the yellow leads from the 3P connector show no continuity to ground (good)

2) Engine-running AC check: I get 38V at idle rpm, 50 volts at 3000 rpm and 80V at 5000 rpm. Checks of all three yellow wire pair combos give about the same value result. (good)

3) Resistance in yellow leads from red 3P to white 6P at the VRR, all show 0.3ohms, which I believe is good.

So at this point I suspect the problem is the VRR. I don't have a good one to swap out and I know your tester unit is already committed at the moment.

If I understand correctly what I've done, I'm getting the right amount of power from the alternator to the red 3P and I don't have evidence that one of the windings is gone / grounded. The wires from the 3P to the 6P connector check out, which brings me to the VRR. At the battery I'm not getting the power from the alternator. Could it be anything *but* the VRR?

 

[John OoSTerhuis]

TK, it sure sounds like the VRR. I'm having a couple of donated VRRs being tested right now. If one checks out I'll have another loaner available. Should know tomorrow.

John

 

[tkhelm]

TK, it sure sounds like the VRR. I'm having a couple of donated VRRs being tested right now. If one checks out I'll have another loaner available. Should know tomorrow.

Hi John, any luck with those new VRRs?

-Troy

 

[John OoSTerhuis]

Sorry Troy, my friend can't get to them until Sat. The STOC loaner VRR should arrive in CA on Thurs and be available to be sent on soon after. If nobody else comes forward with one you're next. Email me your snail-mail.

John

 

[tkhelm]

John, I don't believe I have your email address, and your account here is closed off to PMs. Can you PM it to me and I'll respond with mine? Thanks!

 

[John OoSTerhuis]

Troy, click on my name above my picture and select 'view profile' then 'send email.' Sorry, I don't do PMs here.

John

 

[tkhelm]

Assuming for the moment that my VRR is confirmed as the problem, my next task will be to acquire a replacement. I can't find a current discussion on this forum of the best sources. Online searches show four new and used units (part#31600-MS2-601) on eBay for $90-120 and Rick's Electric offering a new one at $134. Partzilla was >$200. IIRC, John O recommended in another thread against buying new, although it wasn't clear why. What are the merits of new vs used? Any other good sources? There are also aftermarket alternatives...

 

[John OoSTerhuis]

Troy, first see if a voluntary upgrader here or on ST-Riders.net or my-mc-phoenix.com might give you their take-off VRR for free, while you save your money for the upgrade. That's been done a number of times for folks pleading poverty, to get their daily commuter back on the road.

I'd be reluctant to buy a used one off Ebay (or elsewhere) without a money back guarantee if it doesn't deliver 14+V. Not likely. And I'd never pay more than half of the best Internet Honda parts price, not local dealer quote.

I think there's now a couple of aftermarket versions (Caltric, Electrosport, and Oregon), but beside price, IINM they require snipping the OEM white 6P and using individual spade connectors or splicing in their connector.

There's also an authority model version of VRR that some folks have obtained. I've got the Honda part number somewhere.

HTH

John

 

[John OoSTerhuis]

I guess if I wasn't going to ever do the 40amp upgrade I'd buy a new stock Honda OEM VRR from one of the good online parts sources like Service Honda, instead of used/salvage. Keep in mind that whatever fried your VRR may also fry it's replacement, new or used, in short order (yes, it's happened a number of times). There's a number of things that should be done to optimize the rest of an aging charging system to prolong all its components' lives.

 

[tkhelm]

Received the STOC loaner VRR today (thanks!). Installed it with great anticipation and…no joy. Voltmeter shows no increase with the engine on, indicating about 12.8V when it came off the battery tender and falling slowly as I started and stopped the engine as I poked around with the multimeter.

This has me scratching my head, as I can’t figure out what could be wrong if the VRR is good. Here’s what I know using the loaner VRR:

- Double-checking to be sure nothing changed, at the 3P all connector pair combos show same values for each check: 35V (AC) at idle and 40-80V (AC) at higher rpm (good).

- The three yellows between the 3P and 6P show continuity and resistance of 0.3 ohm (good).

I also checked the 6P wires by inserting the multimeter probes up the back of the 6P while it was plugged in to the VRR with the engine on:

- Same AC values as above on all pair combos of yellow wires, so the power from the alternator is getting to the 6P connector.

- Black wire reads 11.7V

- Red/white wire reads 11.8V. This was the same reading as at the two battery terminals at the time—engine at idle and all fuses in (headlight on, etc.). Note that with the engine off the battery terminal reading went back up to 12.4.

- I also checked the resistance between the red/white wire at the 6P and the positive battery terminal with the engine off and got 0.3 ohms, although I’m not certain if that is a valid test since the wiring diagram shows the red/white going to the starter relay. If it is, I think this tells me that if the VRR were putting out >14V that it should travel from there to the battery without problem.

One other data point is that at first I tried to check the 6P wires with the 6P connecter pulled out of the VRR and I got 0.8V (AC) from all yellow wire pairs combos. After some reflection I realized that with the 6P disconnected the alternator wasn’t getting a signal from the black wire to send power, so this should be normal (I think…).

So if the reason I’m not getting >14V at the battery isn’t a bad VRR, where else should I look?

 

[John OoSTerhuis]

Other than a bad battery or the test VRR failed during shipping, I'm out of ideas. Anybody else got any ideas?

John

 

[John OoSTerhuis]

The red/white wire sends the regulated DC charging current to the battery through the main fuse and battery-to-starter relay wire harness.

 

[tkhelm]

Red wire bypass is on my list of To Dos because there has been some melting of the 4P connector around the red wire (don't know if it's recent or from years prior--I had never looked before this recent issue came up). I hadn't considered that as a potential cause of the current low voltage problem.

Would resistance downstream at the 4P connector cause the voltage to be low at the 6P connector/VRR output? Or should it read normal (>14V) out of the VRR and then read differently after the point that is damaged, if that's whats going on?

I'm still trying to get my head around the basics but I had thought corrosion or a burnt but functioning wire would lead to high voltage not low (and eventually do damage to something).

 

[Doodaa]

I once had a similar mind puzzling problem on an old prop driven aircraft that was driving everyone crazy. The problem presented itself in similar confusing tests that everything should have worked correctly, but didn't.
The problem was found to be intermittent (read poor current capacity) number of strands of wire inside a sealed wiring connector.
Think poor battery terminal connection.....small demand (voltmeter or dash lights) are good, but large demand (starter, headlights, charge battery) wouldn't allow enough current flow which caused excessive voltage drop.
Found this in Nam, 1968 in the central highlands and remember the problem to this day~!
Worth a look. It won't show up on a resistance check, but if the voltage drops too much with a known good regulator it means the current capacity is limited and this can be the strands of wire or the terminals in the connector.

Other than a bad battery or the test VRR failed during shipping, I'm out of ideas. Anybody else got any ideas?

John

 

[tkhelm]

Makes sense as a good possibility. Is there a way to test for that, or more importantly, isolate the offending segment or connector?

 

[Doodaa]

If you cannot physically pull it apart and visual inspection cannot locate the problem, then you are left with the substitution of the possibilities with known good wire or connections.
Jumper wires of the same or larger capacity.
I have pulled many poor stranded wires apart where they were broken....the insulation stretches like licorice candy.

Makes sense as a good possibility. Is there a way to test for that, or more importantly, isolate the offending segment or connector?

 

[John OoSTerhuis]

Grasping at straws here, but - try jumpering the red/white wire from near the VRR directly to the + battery post? It's almost as if the charging current isn't getting to the battery... Can you measure the voltage at various points along the line with the engine running?