Overhaul of the Onan 12JC4R generator

I was fortunate enough to acquire this generator last fall.  It was new in 1969 and has unknown hours on it, but it appears in decent shape.  I am going to do a level two overhaul and install it as backup power for my house/shop.  The first order of business is a complete inspection.  I discovered a few problems; the starter didn’t crank, the distributor was loose, and the carburetor had some burned out chunk of metal attached to it.

Onan 12JC4R generator
Onan 12JC4R generator

First, the starter:  These units use a Prestolite MEO3006 starter, which is common to several Chrysler products from the late ’60s and early ’70s.  This is obviously a replacement unit, as it is not “Onan Green.”  When I hooked a battery up and tried to turn the motor over, the start relay clicked but nothing else happened.  I dismounted the starter and removed the starter solenoid.  The interior of the starter motor looked in good condition, which points the solenoid.  Sure enough, I removed the back of that unit and found two wires burned through and a large blackened area.  While I had the starter off, I hooked it up to a 12 volt battery and it worked fine.  A new starter costs $469.00, a new solenoid cost $59.00.  I opted for the solenoid.

Onan 12JC4R burned out generator starter solenoid
Onan 12JC4R burned out generator starter solenoid

The next thing is the distributor.  I was checking the points and contemplating replacing the breaker points with an electronic ignition when I discovered the distributor could turn 1/8 of a turn in each direction, as when making timing adjustments.

Onan 12JC 4R distributor clamp
Onan 12JC 4R distributor clamp

I used a 3/8 box wrench and tighten up the clamp holding the distributor shaft.  It took several turns and makes me wonder why it was loose.  I will have to check the timing with a light once I get it running.  This also could be why the generator was not running when we took it out of service.

Onan 12JC 4R rotor and breaker points
Onan 12JC 4R rotor and breaker points

As for the points, they look brand new, as does the rotor and distributor cap.

Onan 12JC 4R generator spark plug, champion H8C
Onan 12JC 4R generator spark plug, champion H8C

The spark plugs look well used and the plug wires look original.

Finally, there was an electric choke mechanism on the carburetor which is completely unnecessary for a propane fueled unit.  The choke plate itself was wired open.  The electric choke was was burned open, so I removed the assembly.  I then spent some time at the local NAPA cross referencing parts.  Here is a tune up list:

Nomenclature Onan part (old) Onan part (new) Napa Part Alternate
Oil Filter 122A185 122-0193 1084 Fram PH16
Points* 166P245 166-0245 CS709
Rotor 166P234 166-0234 AL58/AL52
Distributor cap 166B307 166-0235 AL91
Condenser* 166P310 166-0310 AL38
Ignition Coil** 166B310 166-0859-02 701002 PRX 405011
Plug wire #1 167A1410 167-1602 701064
Plug wire 2,3,4 167A1409 167-1602 701063
Spark Plug 167-4 167- Champ H8C***
Air Filter 140B640 140-1907 7-02241
Starter 191C324 191-0324 Prestolite MEO3006
Solenoid N/A 191-0433A ST103
*Electronic ignition set N/A 166-0825 Pertronics 1545**
**Ignition coil W/PRX 1545 PRX 405011

*Condenser and breaker points can be substituted for electronic ignition kit, either Onan 166-0825 or Pertronics 1545 with Pertronics PRX 405011 coil.
**Pertronics electronic ignition must be used with Pertronics coil
***Champion RH8C plugs should be used with replacement wires without noise suppression plug boots.

This is for an Onan 12JC generator circa 1969 with a Studebaker engine. Other models/years may vary.  The other issue with this unit is there is no supervisory monitoring and control.  There is no oil pressure loss, overheat or overcrank faults.  This is why the starter solenoid failed.  To remedy that situation, I started to design a better control circuit.  Then I looked around on the inner tubes and found somebody had already done this.  DynaGen makes the GSC400p which has can monitor oil pressure, engine temperature, frequency, engine RPM, hours, voltage and current.  It can fault for any out of tolerance condition, as programmed by the user.

Retrofit generator controller
Retrofit generator controller

I plan to install this in the original control box, leaving the original control circuit intact by using the remote start/stop connections.  I keep the original remote/start/stop switch and hand crank switch in place for use if the fancy controller fails.

The burned contactor fingers

This is a set of burned contactor fingers on a Harris HS-4P 30 amp RF contactor:

Harris HS-4P RF contactor
Harris HS-4P RF contactor with burned finger stock

The back story is this:

The contactor in question is at the base of Tower #3 of the WBNR (1260 KHz, Beacon, NY) antenna array.  This is the tallest of all the towers, at 405 feet.  As such, it gets struck by lightning often.  There was at least one occasion where one of the inductors in the ATU got “sucked in” due to the huge magnetic field of a high current strike.  It is not at all surprising to me to find other component issues in this ATU.  Because of the burned contacts, I’d suspect that the station was switching modes under power, but I didn’t see that happening today.

The problem manifested itself in very high SWR after changing over from day pattern to night pattern.  This did not occur every time, in fact, it only occurred once in a great while at first.  Then, over the last couple of months it began occurring more and more often.  Since the snow drifts are now down to a manageable six to eight inches, it was a good day to go out and do some exploring.

First of all, I put the station into night time mode just to confirm that there is still an issue.  The transmitter, a Broadcast Electronics AM1A showed very high SWR and carrier fold back.  Left it in night pattern, but turned it off and took a walk, not a drive, to Tower #4 which is all the way at the bottom of a hill, near the old City of Beacon landfill.  I figured that I would check that one first, then look at Tower #3 on the way back.  When I got to Tower #3, I found the issue right away.

Fortunately, I was able to salvage a set of contact and contactor bar from another relay in the same ATU that was not using them.

Burned RF contactor bar
Burned RF contactor bar

The night pattern is only 400 watts, but these are tall towers, 225 degrees, therefore current and voltage are high at the base.  In fact, the slightest change at the base of the night time towers will greatly upset things.

Burned RF contactor fingers
Burned RF contactor fingers
Harris HS-4P contactor repaired
Harris HS-4P contactor repaired

This is the repaired contactor.  I will say, the EF Johnson RF contactors are easier to work on.  Those are the ones with the big rocker bar across the top and two solenoids on either side.  All of the wiring, status switches and contacts are exposed and easy to get to.  This one, not so much.  This is the BE AM1A transmitter

Broadcast Electronics AM1A transmitter
Broadcast Electronics AM1A transmitter

It is not a bad unit, compact, sounds good, reliable, etc.  In order to work on the power supply or anything in that top cabinet, the whole thing needs to be removed from the rack and taken down.  I suppose that is my only gripe about the thing.

Better Times at WICC transmitter site

The WICC transmitter site, Pleasure Beach in Bridgeport, has been cut off from normal access since the bridge to the island burned in 1996.  Since that time, access has been by boat with a 0.93 mile walk from the dock to the transmitter building.

Last summer, LVI Construction, under contract from the Town of Stratford, put in a temporary road and began removing the burned out cottages.  While that road is in place, the radio station has been able to access the site and get many important things accomplished.  These include:

  • Replacing the vandal damaged top beacon on the South tower
  • Removing several decades worth of stored crap, garbage, obsolete and unused equipment
  • Repair the electrical service to the building
  • Replace the generator transfer switch
  • Repair the Sonitrol building alarm
  • Replace the old Onan Generator
  • Have the power company replace the 3 phase circuit from the point where the under water cables come ashore to the transmitter building.

All of these projects should greatly improve the reliability of the station.  This should make Bill, happy, who appears to have a WICC chip implanted in his brain because every time the carrier is interrupted he posts about it on the radio-info.com website.

The biggest issue with the site was the utility feed from the shore to the transmitter building.  The original circuit was installed in 1936 when the station moved to the island.  It was old and the poles were all rotting and had horizontal cross arms.  Ospreys especially like the horizontal cross arms as they made good nesting spots.  That is, until the nest shorts out one of the phases catches on fire and burns the top of the pole off.  This has happened several times over the years causing many hours of off air time.

WICC new utility service
WICC new utility service

United Illuminating, the local utility company, was very cooperative and installed new utility poles, wires, breakers and transformers, this time with a vertical phase arrangement, which should keep the Ospreys off of them.  Additionally, the cottage removal project included installing Osprey nesting poles.

Pleasure beach cottages removed
Pleasure beach cottages removed

With almost all of the cottages now removed, the area looks much better than before.  Actually, it should be a nice nature preserve  and hopefully, the absence of the buildings might reduce the number of vandals in the area.  The work is almost done, so the road is about to be taken up. This means we need to wrap up the work out there, so the final push is on.

WICC transmitter building
WICC transmitter building

In the last three weeks, 10 truck loads of junk have been hauled out of the transmitter building and generator shack.   Over 1,500 pounds of scrap steel, 640 pounds of insulated wire, 2,000 pounds of particle board furniture, old t-shirts  and hats (something called “Taste of Bridgeport” which, if anyone knows what that was let me know), old propane tanks, batteries, etc.  We also managed to fix the fence and gate in front of the building, cut down the over grown yew bushes and bittersweet vines.

Transfer Switch
Transfer Switch

The old Kolher transfer switch was also an issue.  There was no place to mount a new switch inside and mounting one outside is out of the question, so the guts from the Kohler switch were removed and replace with an ASCO unit.  This was done in the summer of 2009.  The breaker on the right side is the main service disconnect for the building, which was installed in September.

Onan 12JC 4R air cooled generator
Onan 12 KW 12JC 4R air cooled generator, removed from service

Today, it was time to replace the Onan propane generator.  The old generator is an Onan 12JC-4R air cooled propane unit which was installed on April 4, 1969 at a cost of $1,545.00 new.  For many years, this unit gave reliable service, but it has many, many hours on it and it lacks the fault/self control circuits needed for remote (read desolate) operation.  Several times over the last few years, the generator would run out of gas or the propane tank would freeze up and the starter would crank until it burned out.

It was cold out on the island, with temperatures in the twenties and a bitter west wind blowing right into the generator shack.  All of this conspired to make  working conditions difficult.  Wind chill readings were in the single digits all day long, and in spite of long johns and extra layers, by 3 pm I was shivering and even several hours after coming inside, I still feel cold.

Using tractor to move new generator
Using tractor to move new generator

The new generator is an Cummins/Onan 20GGMA which is rated for 20 KW.  We used a John Deere bucket tractor to move the generator from the flat bed truck to the generator building, then push it inside.  The old generator wiring to the transfer switch was reused, but a piece of flex was used to connect to the generator instead of the solid conduit.  The building fan was also wired up so that it will run whenever the generator is running.

The generator load with all possible things switched on  and the transmitter running at full power is about 12,000 watts, but this would mean the air conditioner and tower lights were on during the daytime.  More likely, the transmitter will be at low power when the tower lights are on and the AC will be intermittent on/off at night.  At full load, this generator uses slightly less than 2 gallons of propane per hour.  At half load, I’d estimate that to be 1.4 or so gallons.

Cummins Onan generator in new home
100 pound propane gas tanks
100 pound propane gas tanks

HOCON gas came out and connected six 100 pound propane tanks in series, which should prevent tank icing.  Propane weights about 4.11 pounds per gallon, therefore the fuel supply should last about 100 hours, or 4.5 days, give or take.  Why 100 pound tanks?  Because we will have to shuffle them back and forth between the dock and the generator shed, a journey of about one mile, in a cart.  Anything larger would be impossible to deal with.  Even so, refilling the propane will be a 2 person job and will likely take all day.

I Got The Air Conditioner Blues

Back in the day, when tube transmitters ruled the broadcast world, common practice was to have a big cooling fan moving outside air through the transmitter building connected to a thermostat.  Temperature swings of 30 to 40 degrees were common, however, the tube rigs could handle almost any temperature that didn’t melt plastic or freeze water.

Today’s solid state transmitters are not that rugged.  They like to have there rooms around 70 degrees +/- 10 degrees or so.  Not to mention the other computer controlled equipment commonly found at a transmitter site.  Things like air chain processors, STLs, remote controls, etc.  So, lots of air conditioning is the norm, and with lots of air conditioning comes lots of maintenance.

Air handler air filters need to be checked and replaced often.  Condenser coils seem to attract every type of flying debris on the planet and need to be cleaned once, possible twice per year depending on tree and weed species near the site.  Even with the preventative maintenance, occasionally things like this happen:

AC condenser frozen dryer and piping
AC condenser frozen dryer and piping

Of course, the entire cooling coil inside is frozen solid.

This condenser is low on refrigerant, causing icing problems.  It has a slow leak somewhere and is about to be replaced.  Other reasons for this happening are malfunctioning or non-existent low ambient kit on the condenser fan.  Sometimes less than knowledgeable persons will install a 5 ton unit designed to run throughout the year but not take into account the effect of moving below freezing air at high speed across the coils.  Insufficient air moving across the cooling coil will also cause this.  Insufficient air flow can be due to plugged air filters or clogged fan/blower blades.

This one is even better (same condenser unit):

AC condenser broken fan
AC condenser broken fan

The fan blade is sheared off and jammed into the condenser coil.  This happened during power transfer from generator power to commercial power.  Naturally, it was at 1 am in the morning after a pole mounted transformer had been replaced.  When the building transfered back to commercial power, I went outside to use the “bathroom” before my two hour drive back home.  I though I smelled something hot, you know that cooked paint/plastic smell, but couldn’t really track it down… the winds were kicking up and another thunderstorm was on the way.

The next afternoon, however, when the sun was up and the site was working on one air conditioner, the temperature alarm went off.  Upon arrival, I found the condenser breaker tripped, resetting it caused the building lights to dim.  The fan motor was shorted to case.  I would theorize the aluminum fan blade suffered from metal fatigue, likely because the blades were not balanced causing a vibration.  When the power transfer occurred, there was just the right combination of torque and centripetal force to cause the blade to rip, then lodge in the condenser coil.

The fan motor has replaced, but I think it is time to replace the whole condenser unit, which will be expensive.

AC&R Gauge set
AC&R Gauge set

I found having a set of gauges to check the head pressure and suction is a good diagnostic tool to quickly pinpoint problems with HVAC units.  This way, when the HVAC tech shows up, you can quickly point him in the right direction.