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Re: (ET) new relay in - now no reverse



RJ,

On Fri, 4 Aug 2006, RJ Kanary wrote:
Prove out all the voltages that SHOULD be present with an ANALOG VOM.High impedance sand based DMMs will lie to you especially at these voltages.
I don't see why a DMM should be inaccurate on voltage. Don't you *want* a voltmeter to have high (very very high) impedance? Otherwise when you connect it in parallel with some circuit element, the combined parallel resistance of the voltmeter and the element you're measuring voltage across can drop some, so the voltage you would read wouldn't be the voltage it normally sees. So, I don't see why you would want a lower impedance on your meter.
Verify that voltage AND current is available at Pad 8 {Wire 41} of Card 1 when Reverse is selected. If this proves out move to Pad 9, {Wire
Alrighty. I'm assuming it should have the full 36V (or 38V, or whatever the pack is putting out) at those points.
38}. If voltage and current is present here, now you can suspect a wiring error at the other relay terminals.If voltage and current is NOT present here, you are about to embark on one of the finer adventures of owning and repairing an AA model E-15, repairing Card 1. :(
D'oh. I'll check it in an hour or two - need to finish making some biodiesel for our cars and furnace first. Given that I thought I heard a "pop" noise when I first put it in reverse after putting in the new relay, I'm unfortunately thinking it's not going to be a simple wiring issue. :( But, if it's just a case of a blown resistor or cap on card 1, that shouldn't be too bad - I've done a fair amount of electronics work in the past. Well, it shouldn't be bad if it's obvious which element blew. :) Chasing down a bad circuit element can be a pain in the tuckus. 

Thanks,
Mike
----- Original Message ----- From: "Michael S Briggs" <msbriggs alberti unh edu> 
To: <elec-trak cosmos phy tufts edu>
Sent: Friday, August 04, 2006 9:35 PM
Subject: (ET) new relay in - now no reverse




So I finally had time to put in a new relay in place of the blown
forward/reverse relay. Forward works fine now - even took it out for a
spin around the neighborhood. When I then went to back it into the garage,
I discovered that when I try to go in reverse, it goes forward. D'oh!
        My first thought was that I had hooked up the forward/reverse
relay wrong. I checked, and nope, it's fine. The problem is that the relay
isn't firing when I move the switch to the reverse-neutral side. I hear
the reverse microswitch click, but the relay doesn't move. Checked the
power connections on the relay, and it doesn't seem to be getting any
power when I move the speed lever to reverse.
 Now, I suppose I could have just knocked something loose while
fiddling with everything in there, but I'm wondering if there could be
some greater problem going on that I'm overlooking (considering all the
failures that I've had - while mowing last week, it stopped running - the
control fuse had blown, and took out the fuse block in the process.
Put in an inline fuseholder in place of the fuse block, with a fresh fuse,
and found that I couldn't go forward due to a blown forward/reverse relay.
Put in a new relay, and now the relay isn't getting voltage to fire. It
seems like each time I fix one thing, something else breaks).
 After putting in the new relay, the first time I moved the speed
control lever to reverse, I thought I heard the sound of something blowing
- wasn't sure though if it was just the reverse microswitch clicking, or
if something did in fact blow. It looks like control of the reverse relay
goes through card#1 somewhere (still need to look over the schematics to
figure out which "port(s)" on card 1, so I can see if something is just
loose, or if something did in fact blow). I should be able to troubleshoot
it ok, but what I'm concerned about is if there might be some greater
problem underlying these little annoying problems. There have just been
too many failures one after another for it to just be a coincidence, I
think.
 Actually - if I had wired the power connections to the reverse
relay backwards, what would that do? From looking at the relay, I assume
it just uses a current through a solenoid to control a switch. If the
current goes the wrong way, the B field would point in the opposite
direction - but since I'm not sure exactly how it controls the switch, I'm
not sure if that would be a problem or not, or if it could blow something.
 So, any tips anyone can offer (again) would be appreciated.

Thanks,
Mike

--

--------------------------------------------------------------
Michael S. Briggs
UNH Physics Department
(603) 862-2828
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