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Rational SCC Oven Burner Blower Issue

Question asked by ectofix on May 29, 2015
Latest reply on Feb 11, 2017 by fixbear

I work in-house and, among some very diverse equipment, I also maintain twenty-one Rational ovens.  Twelve are relatively newer SCC-line units and seven of those are gas heated.

 

On separate occasions, two of our ovens began displaying RESET GAS.  One was very persistent and wouldn't heat in one of its two modes (STEAM or AIR).  I found and fixed the problem, which I'll allude to below.

The other oven's problem was very intermittent.  Function testing it the DIAGNOSTICS panel would only zoom in on which heating mode had the problem, but that was it.  The oven would do everything as advertised and I'd simply have to tell them "Call me if it acts up again."  So it'd be fine for a day or two, then all of a sudden it just WOULDN'T.  FINALLY - I once again did some function testing and found the problem.

 

While function testing the burners and noting their sequence of events, I noticed one burner's blower motor would ramp up to speed (RPM displayed on control panel), then arbitrarily drop out.  Through several test cycles, there was no consistency in that event.  Sometimes it'd stay running and sometimes it wouldn't come on at all.

In doing some testing, the ignition module (which also controls the blower) appeared to be doing everything right.  I got down to scrutinizing the burner blower and its connections when...AHHH...the wires going into the motor's connector...fell out in my HANDS!

 

Here's a photo of the connectors I'm talking about.  On floor model units, there are TWO hot air heat exchangers, so the will be THREE burner blowers:

 

photo 1 w plug.jpg

 

 

Those are each five pin connectors with three wires to connect to the burner blowers - AND are a cheesy setup. The plugs are assembled similarly to quick-splice connectors (pictured below) that don't require stripping the wires. I refuse to use that type of wire splice as it is, so having a factory connector which assembles that way on a high end combi-oven is a bit disappointing.

 

quick splice connector.png

The blower leads themselves are already smaller gauge wires and I've discovered that vibration from the motor eventually causes the connector to gnaw its way through the wire strands one at a time. If this is happening, ultimately the blower will begin working intermittently or not at all - although the wires may appear intact while looking at the plug.

 

So, if you happen to notice that a blower isn't running or it sporadically stops running, carefully mark each wire so you remember where they go - j-u-s-t in case.  THEN - give those wires each a gentle tug. You might find one (or all three) will drop right out of connector.

 

If those wire connections are falling apart in your hands, don't despair for not having another wire harness on your truck. ఠ_ఠ

 

With a little study of the plug, you'll find that after unhitching a few locking tabs, the connector can be pried apart (an inner section will slide out of the outer section) far enough to open it up. Remove any remnants of the old wire strands and insulation, then lay the marked and freshly trimmed leads back in there in their assigned locations and compress the plug back together. The act of compressing the connector together will complete the connection - just like those dastardly wire splices I'd mentioned earlier.

 

If you happen be called to work on an oven on which those wires have already "taken the leap" out of the connector, carefully study upon the OTHER burner blower's wiring.  It's wired the same way, so it can serve as your wiring diagram.

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