Whiskeymac Posted July 11, 2019 Share Posted July 11, 2019 My Omni-Step deployed down then stopped working, very simply put. I removed the bolt connecting the drive prongs to the steps and zip tied them up to enable driving. I am now trying to diagnose the problem.Connecting 12 volts across the purple and orange connections to the motor operates it in, then polarity reversed, out, so nothing wrong with the motor.Using my test meter, Earth to these with the cutout button depressed gives 4.71v, and 0.0v when released. This seems a very low voltage. I did attach a fresh earth in case that was the problem, but clearly it isn't.There is the double changeover switch just inside the side door which normally drops and retracts the steps. There is also a retract only switch on the dash for use with ignition on. Neither work now, but the buzzer warning, on the multi control panel above the door, works when the ignition is on.The changeover switch connecting cable has a white, a green and a brown lead. Voltage readings are as follows:Earth to white 3-6v (never steady) .11v switch down, .28v switch up.Earth to green 4-6v (never steady) .29v switch down, .11v switch up.Brown to green 5.7v, .23v switch down, 0.0 switch up.Brown to white 6.0v, 0.0v switch down, 0.19v switch up.I have an electobloc 101. On the extreme right, next to a row of fuses, is a picture of a fuse, labelled Grundlicht (Baselight) / Trittstufe (Step), Polyswitch. I think that this relates to the advice given by a very helpful parts man at Brownhills, that it's a self resetting fuse (1 minute), but I have no idea where it is. Inside the electroblock?The Omnistor (Now Thule apparently) circuit diagrams just show a fuse. My setup is Omnistep with Warning Buzzer, not the alternative with the addition of a Relay for Automatic Retraction. No relay is shown for mine.I happen to have a spare, new motor assembly, thanks to a fool who drove over my steps years ago, but since the original work fine on a direct power feed, I don't think it's worth swapping. The original is clean and the cutout switch works fine.I am lost now so would appreciate any knowledgeable advice. Link to comment Share on other sites More sharing options...
Alanb Posted July 11, 2019 Share Posted July 11, 2019 Hi, My experience is with a slide out step, but I believe the basic principles remain the same. I confirm that the Electrobloc EBL101C diagram shows a self resetting fuse or Poly Switch supplying the step and a floor or step light. The outputs are at Block 4 with pins 2 and 3 supplied in parallel from the Poly Switch, with the -ve connection at pin 6. The Poly Switch will be internal to the Electrobloc. I would expect it to be PCB mounted. Since you have supplied your step directly with 12V, and confirmed that it is functional, is it not possible to go further back and supply 12V via a 20A fuse and blade connectors, to the connector when removed from the Electrobloc? This would confirm that you have an Electrobloc and not a wiring problem. For information. In normal operation of the step, the motor is allowed stall at the end of travel, before the button is released. This means that the motor will be drawing the maximum possible current limited by its own resistance, and that of the wiring and switches. The control switch has the onerous duty of breaking this current. (My step is fused at 25A not the 10A of the Poly Switch.) The manual switch is actually two elecrtically independant single pole changeover switches. The connections are such that 12V -ve (earth) is connected to both sides of the motor with the button normal. Pressing either end of the button connects one end of the motor to 12V +ve. Hope that this is of some assistance. Alan Link to comment Share on other sites More sharing options...
Nicepix Posted July 11, 2019 Share Posted July 11, 2019 Do you hear the motor turning when you operate the switch? If so check the cog on the motor that drives the rack of the step. They have a tendency to shear or lose teeth. Link to comment Share on other sites More sharing options...
plwsm2000 Posted July 11, 2019 Share Posted July 11, 2019 Whiskeymac - 2019-07-11 4:38 PM .... The changeover switch connecting cable has a white, a green and a brown lead. .... I am a bit confused as I don't see how the changeover switch can work with only 3 wires. The switch normally has 4 wires (0V, +12V inputs; motor + & - outputs) and just inverts the polarity going to the motor as required. With only 3 wires, you might have some extra relays somewhere or a control unit between the switch and the motor. The fact that the wire colours on the switch are not the same as the motor wire colours must mean they are not directly connected. Do you have a schematic that you could post? My step draws about 3Amps when moving. I guess if the motor mechanism is quite dirty, it could take a much larger current and trip the polyfuse that Alan mentioned. Connecting another source of 12V directly to the motor may work if has a higher current capability. It might be worth trying to measure the motor current when driven directly from 12V (but beware that your DMM may have a 10Amp fuse that may pop!) Link to comment Share on other sites More sharing options...
Whiskeymac Posted July 13, 2019 Author Share Posted July 13, 2019 No. Complete silence. When 12v is applied to the motor, it works perfectly, but when the switch is operated, nothing like that is applied. See the reading I've listed. Link to comment Share on other sites More sharing options...
Whiskeymac Posted July 13, 2019 Author Share Posted July 13, 2019 Yes plwsm2000 I'm confused too. The diagram that came with my replacement steps and motor is identical to the first down user manual download at this link: https://www.thule.com/en-gb/gb/motorhome-accessories/steps/thule-double-step-12v-_-thule%20step%2012v%20double%20380 Sorry, I can't get the link to pass through the forum link processor.That diagram shows purple and orange wires going to he switch, which indeed, has 4 wires to it. My switch has just the 3. The white and brown seem to go to the down press and the green to the up press.I have traced orange and purple wires going from the motor all the way along behind my cooker, sink/drawers, and fridge, They disappear at the back of the heater cupboard but there is too much in the way to see where and how. There are no connection boxes that I can feel. Link to comment Share on other sites More sharing options...
Whiskeymac Posted July 13, 2019 Author Share Posted July 13, 2019 Thanks alanb for the brief on the electrobloc. I'm not greatly familiar with elecctroblocks and their layout but should be able to follow what you have told me. This will need a clear head that's not rushed and I have a busy day today and am away with the van tomorrow and have to tidy it up beforehand. I'll get back to sleuthing on Monday and see if I can come to any conclusions.Are you familiar with my 3 wire switch by the way? Link to comment Share on other sites More sharing options...
Whiskeymac Posted July 13, 2019 Author Share Posted July 13, 2019 For alanb.I found free time to look at the elecrobloc and was unsure of which pin was which, until I removed the plug and saw some numbered on the circuit board. Corresponding, the wires going to pin 3 & 6 were labelled Grundlicht. Pin 2 has no connection. So just to confirm, your suggestion is to remove the plug and apply 12v to the Grundlicht plug terminals, then see if the steps can be operated again? I can also meter the voltage from the electrobloc pins 3 & 6. Thought I'd better confirm that with you before proceding. Whilst tidying away, ready for departure, I quickly metered across pins 3 & 6 and got 14v. Link to comment Share on other sites More sharing options...
Alanb Posted July 13, 2019 Share Posted July 13, 2019 Hi, Yes my suggestion is to build upon your testing of the step with direct application of 12V to the orange and violet wires, which seem to be standard colurs by moving back to the plug at the Electrobloc and applying a 12V supply there. If the step functions OK, the the fault is in the Electrobloc, but if it remains inoperative then its something in the middle. Unfortunately measuring the output of Electrobloc off load is not conclusive. There could be considerable resistance in the supply which would have little effect on your very sensitive multimeter. Making connections for an onload voltage reading could be problematical. The ability to light a 21W indicator bulb from the outlet could be more revealing, but again it takes some rigging up. For direct operation of the step a switch with only 3 wires is a non-starter. As has been said, the system requires 4 wires. 12V +ve & -ve, plus orange and purple wires from the motor. When automatic retract is fitted, the orange from the step would go direct to the common contact of the relay. As your orange and violet wires do not go to the switch, I can make a guess and suggest that there is a separate control unit hidden somewhere. This could be as simple as a pair of changeover relays operated by the door push buttons. Your dash mounted control switch could also operate the retract/raise relay. Having relays connected as above also provides another possible failure mode. The Electrocloc could be fine, but the supply for the relay coils could be missing. (Either +ve or -ve.) Alan Link to comment Share on other sites More sharing options...
Whiskeymac Posted July 14, 2019 Author Share Posted July 14, 2019 Thank you. Lots of food for thought. How very frustrating is the lack of info for the model. In the handbook there is a fault finding verdict of fuse blown. How very helpful! I'll try to make progress from tomorrow. Link to comment Share on other sites More sharing options...
Alanb Posted July 14, 2019 Share Posted July 14, 2019 Hi Whiskeymac, I strongly suggest that you look at the final post in this thread. It may not be your model, but I think that you will find it interesting. Alan Link to comment Share on other sites More sharing options...
snail Posted July 15, 2019 Share Posted July 15, 2019 Hi whiskeymac, just to say the relay thing ems 03 on our 2005 classic is mounted behind the outer fridge grill where the burner is, Worth a look? Link to comment Share on other sites More sharing options...
Whiskeymac Posted July 16, 2019 Author Share Posted July 16, 2019 I found time at last to apply myself to some testing, utilizing a fuse holder into which I inserted a 20amp fuse and cable to insert small blade connectors to the removed block 4 plug, wires that correspnd to pins 3 & 6. Connecting cable to a 12 v source blew the fuse. The same happened with the motor isolated and the control switch unplugged. The problem would therefore appear to be in the cabling, but I can't think where to test next as I'm unaware of any junctions. With regard to relays, the only ones I'm aware of are in the engine compartment and under dashboardfuse boxes. These are not listed in the vehicle handbook but are presumably base vehicle kit. I have looked in all storage compartments and there are no relays to be seen.There are a couple in the mains cutout switch box, but presumably mains associated. Link to comment Share on other sites More sharing options...
Whiskeymac Posted July 16, 2019 Author Share Posted July 16, 2019 Well that relay would make sense, but where might it be? Very well hidden certainly. At least I know what it looks like but I've been in all cupboards and not spotted it. I may have to use a mirror to look around the walls of the heater cupboard. I really hope it's not there!! Thanks for the link. Link to comment Share on other sites More sharing options...
Whiskeymac Posted July 16, 2019 Author Share Posted July 16, 2019 Behind the outer fridge grill!!!!! Germans really do have a sense of humour!! I'll go and look. Thanks for the tip. Link to comment Share on other sites More sharing options...
Whiskeymac Posted July 16, 2019 Author Share Posted July 16, 2019 Looked behind the fridge and there is a relay there, but it's a 1inch black cube labelled 295.2089.00 and 46/04. It's screwed onto the back of the Dometic fridge and all wires hug the back of the fridge. Must be just a fridge relay. Nothing visible behind the top grill. No cables not terminating at the bottom. Link to comment Share on other sites More sharing options...
Whiskeymac Posted July 16, 2019 Author Share Posted July 16, 2019 Well that relay would make sense, but where might it be? Very well hidden certainly. At least I know what it looks like but I've been in all cupboards and not spotted it. I may have to use a mirror to look around the walls of the heater cupboard. I really hope it's not there!! Thanks for the link. Link to comment Share on other sites More sharing options...
Whiskeymac Posted July 16, 2019 Author Share Posted July 16, 2019 It was there. On the back of the cupboard front, to the right of the door, fighting for space with two other massed cable runs. Only identifyable by using torch and mirror. No screwdriver short enough without fouling the heater, so used ratchet and bit, backwards, mirror image guided. The second screw was under a large, taught cable clump which only with much force gave just enough access. It took half an hour to remove the two screws. Nightmare.It's a large unit, 4 inches square. Is there any way to test it with a meter? I will repeat the 12v from the bloc 4 plug with the EMS 02 unplugged, just to be sure that there is no other short. Link to comment Share on other sites More sharing options...
Whiskeymac Posted July 17, 2019 Author Share Posted July 17, 2019 12 v test completed and no short this time. Interestingly, one plug going into the EMS 02 has 1 green wire, 2 white and 2 brown. Tracing these they come from 2 cables. The one with a white, green and brown matches the switch plug wires and the other has just white and brown that I would guess goes to the up only switch on the dash. The second plug going into the EMS 02 has 2 blue and 2 brown wires, 2 coming from a black cable, the others staying as wires in a cluster that go behind the heater. My guess is that they are jointed to the orange and purple wires that go to the motor which disappear behind the heater. Testing the 4 pins for the smaller plug socket on the EMS 02 there is zero resistance between the two brown wire pins and also between these and one of the blue wire pins. I interpret the latter as diagnosing a short circuit. Sliding out the contents of the EMS 02 reveals a circuit board where the main components are two relays, FRA2C-C2. I can't find these online, though there are plenty of FRA2C-S2s at a couple of pounds each. A bit of research and soldering could save £70. I am seeing a friend today who spent many years working with a soldering iron so I'll start there. Of course it might be a different faulty component. Perhaps also time to go and visit my old friend who makes sound effect kits for the music industry. Link to comment Share on other sites More sharing options...
plwsm2000 Posted July 17, 2019 Share Posted July 17, 2019 According to the datasheet, the FRA2C-C2 is an open frame type whereas the FRAC2-S2 is a sealed relay. The -S2 is slightly larger (due to its case) but the PCB footprint is the same so would be a drop in replacement assuming the PCB has a couple of mm extra space around the relays. Obviously the 12VDC rating is important!. Here is a screen shot of the relevant page in the datsheet. I also attach a screen shot showing how the relays are probably wired in the EMS02 (note this is just my guess of what is inside the EMS02 and is not an accurate schematic of it). Unless there is other stuff inside the EMS02 to drive the relay coils, it should be quite easy to check the relays without desoldering them. Link to comment Share on other sites More sharing options...
Alanb Posted July 17, 2019 Share Posted July 17, 2019 pwlsm2000, You seem to have spent some time in research and drawing to provide your contribution. I do hope that it is appreciated. Whiskeymac, I applaud your "repair it if possible" approach. Carry on the good work as far as possible. Alan Link to comment Share on other sites More sharing options...
Whiskeymac Posted July 17, 2019 Author Share Posted July 17, 2019 Thank you pwlsm2000. Very much appreciated. The relays on my board are in fact sealed. I have tried to drop a screen shot of a photo, but got the message Operation Not Allowed when I tried to submit it. Still a learner. Link to comment Share on other sites More sharing options...
Whiskeymac Posted July 17, 2019 Author Share Posted July 17, 2019 The circuit board has one transistor (3 legged pot), 2 relays and a number of resistors. It would be nice to send a photo but that seems to be beyond this forum's capabilities. Could you please instruct me on how to test the relays without detaching them as you suggest. Link to comment Share on other sites More sharing options...
Keithl Posted July 17, 2019 Share Posted July 17, 2019 Whiskeymac, There have been several posts about posting photos but basically it needs to be below 200 kB file size and .jpg (and NOT .jpeg) format. Keith. Link to comment Share on other sites More sharing options...
Alanb Posted July 17, 2019 Share Posted July 17, 2019 Whiskeymac, Posting Photos. When my aging memory fails me I return to this thread , which I have bookmarked. Alan Link to comment Share on other sites More sharing options...
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