91 Marathon 36v slow go

[boatcrazy67]

Anything I can test or do myself? I did take the motor off to inspect it. Everything seemed ok, the brushes looked almost new.

[JohnnieB]

I was thinking more along the lines of a heavy coat of carbon dust from the brushes causing a conductive path between the various terminals (A1, A2, S1 & S2), bypassing the field and armature windings.

With the cables disconnected, measure between the A1 & A2 studs with and
Ohmmeter.
You should read very low Ohms. Something in the 5Ω range more or less.

Repeat for the S1 & S2 studs, about the same Ohmic value.

Now measure between the A studs and the S studs. Then measure from the A studs to the case and from the S studs to the case. All of these reading should be a very Ohmic value, preferably 1,000,000Ω or more.

[boatcrazy67]

I havent given up on this, had to wait for the snow to melt. I performed the test on the motor, cables disconnected. Here is what I go with my DVM set at the 200 ohm setting.

A1 & A2 reading .5

S1 & S2 reading .4

A1 & S2 reading 1.0

A2 & S1 reading 1.0

Each terminal to motor case = 1.0.

All of these results seem to match what you said they should be. It caused me to have another question, there are 4 terminals on motor,all in a straight line. How can I make sure I have the cables hooked up to the correct terminals. The diagrahm I found on site has all the terminals labled (A1, A2, S1 and S2, but they are not layed on a straight line.

Looking at the back of the engine case, from the left rear wheel looking towards the right rear wheel, from left to right the cables are connected in this order:

S1 - A2 - S2 - A1

Is that the correct order? I can take a pic or draw out a diagrahm if needed. Thanks.

[scottyb]

The case is most likely marked (stamped)

[JohnnieB]

That sounds like the right stud sequence. Drawing attached.

These readings are much to low:

A1 & S2 reading 1.0

A2 & S1 reading 1.0

Each terminal to motor case = 1.0.

They should be very high and they are very low.

[boatcrazy67]

I retested stud to case With DVM set to 2M I get reading of 1. On each stud. Is that a reading of 1,000,000?

Also I went back and retested a few things based on an older threadni found.

Voltmeter test from M- to B+ with FNR in F. The voltage goes from 0 when solenoid clicks to 33.9v with pedal to floor. The FPV is 37.8.

The voltage between M- and B+ with pedal on floorwhich was 33.9 is lower than voltage at B- and B+ on pedal on floor which is 36.0.

The prior thread said if those two readings don't match either the controller isn't being told to open fully or the controller isn't doing what it's told to do. Prior test on pot box tested good.

Does all thiß point to a weak controller? If it were you guys is that what you would replace? Thanks.

[JohnnieB]

I'd figure out why the battery pack voltage is only 37.8V and fix that problem.

Then start troubleshooting with fully charged batteries. (38.2V)

[boatcrazy67]

I replaced some of the battery cables with new 2 awg cables. The old ones looked good but with the new ones the BPV is now up to 38.2 volts after charge and rest period.

Still same issue. I put the positive DVM on each terminal on the motor and while on the slope and after coming to a dead stop on slope due to loss of power the voltage at each terminal on the motor was about 32 in forward. Is that what the voltage should be?

At this point I'm thinking of upgrading the controller and solenoid but would hate to do so if the issue is the motor or something else. At loss for what to next.

[JohnnieB]

The battery pack voltage dropping to 32V under heavy load is okay, but try not to drop it below 27V under any circumstances. However, that voltage measurement is at the motor, so it isn't actually battery pack voltage. You may be loosing some voltage across the cables and F/R switch contacts and through the controller.

Suggest replacing the rest of the high current cables. All 13 (or 14) should be the same gauge, 4Ga or thicker throughout.

I'm surprised the voltage on all four stdus on the motor were reading about the same voltage. A1 connects directly to B+ and A2 connects to S2 via a set of F/R switch contacts and S1 connects to B- via another set of F/R switch contacts and the controller.

Therefore with the voltmeter's negative test lead attached to B- and the pack voltage at 32V, you should get Zero volts on S1, about 16V on S2 & A2 and 32V on A1.

[boatcrazy67]

Now I know what a cat chasing its tail feels like. Keep running in circles and not making any progress.

Since my last update I have upgraded the controller and solenoid and micro switch on the pot box. I get a click when I push the pedal. In forward gear with the key on I am getting voltage at all the terminals on the motor. About the same voltage on each one, 33v more or less. The motor does not turn.

I even took the motor out to inspect and it looks fine, brushes are good. What in the world is going on? Thanks.