I'm Not Sure Why, But I Now Have a B-80

[BradKahler 177]

28 minutes ago, Handy Don said:

This isn’t clear to me, can you explain further how you tested?

Do you have a rectifier bridge or a voltage regulator there? Bridges are easily tested with a VOM using either the DCV setting and a battery or else the diode setting sans battery. But a VR is isn’t really testable with VOM alone--it needs both an AC input and a 12v reference supply. 

Many of the the VRs that I’ve encountered (including on both the Onan P218 and P220) have one of the stator terminals directly tied to the 12v output terminal. That could look like a short. 

 

The Amazon listing refers to it as a rectifier so I am assuming it is a bridge rectifier.  On the B80 rectifier there are no markings on or near the terminals so it is unclear which two are the ac input connectors and which is the B+ connector.  When it was installed, the two AC wires from the stator were connected to the A & B terminals.  The ignition switch was connected to the C terminal.  The original plug was gone and someone had spliced the two wires from the stator to make them long enough to reach.  

 

Using my DVM Diode setting I get the following readings:

 

Negative cable to A and Positive cable to C I get .000 (I get the same reading when I swap the cables) 

Negative cable to A and Positive cable to B I get no reading.  Same if I swap the cables, no reading.

Negative cable to C and Positive cable to C I get no reading.  Same if I swap the cables, no reading.

When testing in Diode mode, I believe I should get 0 in one direction and 1.5 or so in the other direction.  

 

When I switch to Resistance mode I get the same exact readings as in Diode mode.  I've used diode mode before on other projects and it works correctly for those.

 

For a quick test I pulled the connector off of the B100 to test it and the regulator tested good using the Diode mode assuming B is B+ and A and C are the AC inputs.  

 

I believe this regulator is not original, at least I don't think it is.  T

 

 

This the best picture I have of the B100 rectifier.  It looks totally different than the B80 rectifier.

 

 

 

This is the rectifier that I've ordered to replace the B80 regulator.

 

https://www.amazon.com/dp/B019DHPM44?ref=ppx_yo2ov_dt_b_fed_asin_title

[Handy Don 15,050]

Agreed not original.

 

Apologies in advance for pedantry below...

 

I”ve never seen a WH Kohler with a rectifier. Tecumseh, yes.

 

People often (simplistically) refer to VRs as rectifiers. However, rectifiers only convert AC to DC. A VR contains a rectifier but also limits the voltage that is charging the battery. An important difference indeed to prevent cooking the battery. What does it do with the excess voltage? It converts it to heat--hence the cooling fins on the stock VR and the need of ALL VRs to have a way of transferring heat out of the device. 

 

Since the tractor originally had a VR then the engine has a stator configured with two wires out to deliver the AC. As I noted before, many VRs link one of the stator terminals to the B+ terminal--if so, across those two terminals expect 0Ω in resistance mode and connectivity in both directions in diode mode regardless of polarity. In that situation, swapping the connections for the B+ and the linked terminal would let the electrics behave normally. Not knowing how that VR is internally wired, I cannot predict how external DVOM-only testing should work or whether it is still viable. 

Edited 12 hours ago by Handy Don

[BradKahler 177]

No apologies needed.  I've not dealt much with small engines, at least when it comes to servicing them so explanations do help.  That info does explain why Diode mode is not really applicable. 

 

What would the reading differences between the B80 and B100 regulators indicate?  Or as you mentioned above,  different regulators could give different readings on a multimeter?  

 

It sounds like the best test is to just try it and see what happens, once I get it rewired that is.  

 

However, probably my biggest question is how do I know for certain which terminals are AC and which is the B+ ?

 

 

[Handy Don 15,050]

8 minutes ago, BradKahler said:

It sounds like the best test is to just try it and see what happens, once I get it rewired that is.  

 

However, probably my biggest question is how do I know for certain which terminals are AC and which is the B+ ?

Yes, testing is the way. The VR only comes into play after the engine in running and a good battery will keep an engine running for at least 30-45 minutes without being recharged. 

Typically, the terminals are labeled. On the one you have, per your labels, I’d guess A & C are stator and B is battery. There is little risk in doing quick tests of different configurations, but a VR does need a viable 12v batter connected to operate properly. 

Before going too far down the rabbit hole, I’d confirm that you are getting voltages from 10 to 35 out of the stator (based on engine speed) without the VR connected. 

[BradKahler 177]

22 minutes ago, Handy Don said:

Yes, testing is the way. The VR only comes into play after the engine in running and a good battery will keep an engine running for at least 30-45 minutes without being recharged. 

Typically, the terminals are labeled. On the one you have, per your labels, I’d guess A & C are stator and B is battery. There is little risk in doing quick tests of different configurations, but a VR does need a viable 12v batter connected to operate properly. 

Before going too far down the rabbit hole, I’d confirm that you are getting voltages from 10 to 35 out of the stator (based on engine speed) without the VR connected. 

 

Thanks. 

 

I might hot wire the ignition system tomorrow so I can start the engine.  If I do so I'll check the stator output.  I've been wanting to verify my carb rebuild is good but a bunch of side issues, like burned up wiring,  keep getting in the way.

 

Stay tuned....