Technical Elusive relay

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Technical Elusive relay

tugboat

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Hi all, new member to the forum, friends call me Tuggy.

I have a motorhome based on a Ducato 2.8jtd. When the engine is started the habitation 12volt is switched off automatically and the step also automatically retracts if you have forgotten to do it.

This has just failed and I'm struggling to find a failed relay or loose contact. The Bessacarr 725 manual only deals with hab stuff and the Ducato manual only deals with the base vehicle. Neither seem to deal with the interface between the two.

I don't think the problem will be individual to step or hab electrics but something further back up the line that affects them both.

I've checked all visible connections and fuses under the hood but have no idea where the relay in question is positioned. Can anyone help please?

I'm guessing it will be a 'normally closed' relay that opens when it detects output from the alternator? I'm no mechanic but blessed with decent common sense. Quite able to use a multimeter if necessary.

Thanks for any advice.
 
Hi Tuggy, (name seems familiar, MHF perhaps...?)

I had an older Bessecarr (1998 625) and I recollect that the relay that switched off the 12v supply to the habitation side when the engine was started was located under the wardrobe floor next to the charger unit (because I disabled it :eek:)

There were two relays side by side so the other one may have been for the step/fridge.
 
Hi Tuggy, (name seems familiar, MHF perhaps...?)

I had an older Bessecarr (1998 625) and I recollect that the relay that switched off the 12v supply to the habitation side when the engine was started was located under the wardrobe floor next to the charger unit (because I disabled it :eek:)

There were two relays side by side so the other one may have been for the step/fridge.


Hi guys, yes MHF that's me!(y)

Thanks for the heads-up re looking in the wardrobe. I did check all the breakers etc on the main charger unit, but I'll have a look underneath where the Truma is.
 
Swift Group vehicles on the 2.8JTD had fuses and relays associated with these functions on a bracket under the black plastic (Fiat fitted) cover to the centre top rear of the engine bay.
 
Have you checked that you are getting +12v at the alternator on the D+ terminal when the engine's running?
This is the signal that operates the fridge/step retract relay and isolates the mains hookup amongst other things.
If it's an OMNISTEP have a look at http://www.motts.org/Omnistep.htm wiring diagram. It does not tell you where the relays are located but on lots of MHs they are located near the fridge and near the exit door. On some motorhomes (mainly continental) they are incorporated into the 12v charger/control panels (elecktrobloc) which makes life a bit easier.
Try contacting the manufactures, they will have the wiring schematic and location diagrams you need. I find them reasonably helpful if you can get to speak to their technical department and extol their virtues on motorhome forums etc.
Adria sent me pdf's by return when I had a similar internal wiring problem.
Hope you track it down.
 
My van has the Omnistep relay and the fuse under the gray plastic liner behind the passenger door. The circuit is connected to both the battery positive and the alternator field terminal.
 
A post from varesecrazy reminded me that I had a problem on my Bessacarr from a failure of the 'quality' Swift connection to the 12v signal wire to the alternator which consisted of a scotchblock!
 
...with reference to my post above, see here:


http://www.outandaboutlive.co.uk/forums/Motorhomes/Motorhome-Matters/12-Volt-Isolation-Relay/35496/


wink.gif
 
OK guys, here's what I have done.
Here's a pic with the cover removed from fuse/relay box in top of engine bay
P8100001_zps3ac872c8.jpg

The 2 relays top right are identical
P8100002_zps7d385259.jpg

Sorry for out of focus, macro on camera not working properly
P8100003_zps53522043.jpg


My understanding of the symbols on the relay, is that when you apply 12volts across 85/86, the previously closed circuit across 30/87 should become open circuit. Am I right in that.

In actual fact, on both relays, I have open circuit with or without 12volt across 85/86. I can hear the relays clicking, in fact I took the cover off one and watched it moving.
The fuses in the first pic are all OK, it seems odd that both relays should fail at the same time. There was no evidence of sparking/burning of contacts in the relay I opened.

I dunno, I'm flummoxed!
 
First of all, they are the fuses and relays I expected.


I think you're reversing the logic. I'm pretty sure they are SPST (single pole single throw) relays, and that energising 85/86 should complete (energise) the circuit 30/87.


I'd recheck this functioning of the relays.


If the relays now check out, and the fuses are all OK (and I would do a continuity check with your meter, rather than simply a visual) then the next thing to try is whether you are getting a D+ feed from the alternator which should form the input to the switching side of both relays (with the engine running).


You can probably download the appropriate wiring diagram (by year) from here:


http://sargentshop.co.uk/epages/eshop328964.sf/en_GB/?ObjectPath=/Shops/eshop328964/Categories/TechData/%22System%20Schematics%22/%22Swift%20Group%22


..and if you can, the relays are quite obvious, and the wiring colours should help (I'll bet the brown is the D+ feed).


Edited to add.


I saw an example of similar problems which defeated diagnosis (as fuses/relays were OK) until the wiring was traced from the fuses round the back of the battery, where the wiring was obviously damaged (ostensibly by acid leakage). It may be worth tracing the wiring form the fuses!
 
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Hi,
The relays were checked with the meter, hence my statement that they are open circuit regardless of whether 12volts is applied.

I'm thinking I need to let the pros look at it. The van is still under (secondhand) warranty but the dealer is 80miles away and have so far been pretty hopeless at fixing other issues so I don't have much confidence in them.

I'll be having strong words with them this week, with a view to getting the problems sorted locally to me, and them footing the bill.
 
These are normally closed relays, 30/87 is conductive when the coil is not powered.
Such relays are cheap and easy to exchange!
 
I'd expect a 4 terminal NO (Normally Open) relay, both from experience and the Swift wiring diagrams.


The Alternator D+ signal normally provides switching (closing) to enable the leisure battery charging via one relay, and the Fridge 12V supply and step retract via the other.
 
Bit of an old problem Tuggers ;)

I'll see if I can find anything from another source.

Kev.
 
common problem.. Had to fix mine on our apache 700 2 weeks ago before we left..
On the left hand side of the step (under the van) is a white square plastic section that contains a spring loaded switch. This gets cloged up with dirt etc..
If you locate it you can pull out the whole part, wires are attached to the rear so just pop it out and then spray in some switch cleaner (maplins) or use some light oil or WD40 to clean the crap out.. You should get the spring part freed and bingo.. Off you go.

From Fun.




http://www.practicalmotorhome.com/f...ctby-switch-or-starting-engine-ci-carioca-644
 
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Thanks for that Kev, but as said previously, I don't think the problem is with the step as 2 other issues happened at the same time, i.e. the hab 12volt not switching off and the fridge not working on 12volt with engine running.

IMHO the problem is that a component has failed further back up the line that is causing the problem with all 3. There must be a relay that activates when the engine is started which then ...
a) Causes the step to retract
b) shuts off the hab 12volt
c) provides a 12volt supply for the fridge

Anyway, I've finally had a talk with the dealer today who has authorised me to get the outstanding issues (including this one) fixed locally and they will pay.

I had just hoped to identify the fault myself and maybe replace a fuse or a relay and save some hassle.

Hopefully when it gets fixed, I can find out which bit failed. And why.
 
IMHO the problem is that a component has failed further back up the line that is causing the problem with all 3. There must be a relay that activates when the engine is started which then ...
a) Causes the step to retract
b) shuts off the hab 12volt
c) provides a 12volt supply for the fridge


....as above, there is.


The two relays you've found control, respectively, i) the leisure battery split charge, and ii) the fridge and the step retraction (as per the referenced wiring diagram on the Sargent website link also shown above.


AIUI, the 12v habitation isolation is internal to/controlled by the Sargent control unit (sensed on the same Fridge/Step relay output).


The items I would check would be the D+ signal into the two relays, the relays themselves (and I still think these are NO (normally open) relays), the adjacent fuses (fridge and step normally on the same one), and if these check out OK, then the wiring from the fridge/step relay to the units themselves is suspect.


You can probably check out the D+ signal (at least at the first level), by seeing if the leisure battery voltage increases when the engine is running - this will confirm that the alternator is delivering a signal to the split/charge relay, but not that it is getting to the other, step/fridge relay. (If it doesn't increase, then either the D+ signal is missing, or the split/charge relay is duff). If it does increase, then you know you have both a D+ signal AND a working split charge relay. In this case, I would be inclined to switch the two relays, and try again (as this will identify or eliminate a problem with the step/fridge relay).


As already stated, I have seen the problems you describe on a similar 'van, and caused by wiring damage on the output from the relay/fuse set behind the vehicle battery - ostensibly caused by acid damage.
 
That's all excellent thinking Mr Hampton, er, I mean Mr Jampton. I've just got home and seen this post so I'll have a cuppa then go out and check the LB voltages.

I'm still puzzled why both of those relays should show open circuit with and without 12 volts applied. I have heard and seen them clicking so know the solenoids are working OK, plus there is no sign of burned contacts. I no understand!

I shall return forthwith. I appreciate your advice.
 
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