Generator Fan Blower

[Richard Barnes]

After running over a truck tire that disentigrated in front of me, my generator baffle was pretty much flattened. The generator shut down and the rear a/c shut down with a P-5 warning light. I understand that the baffle is critical to proper functioning of both and Jon has sent me the contact information to order a new baffle.

The next problem is that I can't get the blower to come on at all now. The generator starts fine but no fan. I've reset the breakers on the generator and checked the fuses located on the generator and everything looks fine.

Am I missing a fuse or breaker or do I have a more serious problem? Thanks for any help or advice.

[Richard Barnes]

I also checked the fuses for the "evacuator fans" (located in the bay with the radiator) and they were both okay. Thanks for any suggestions.

[phorner]

Richard,

I had a problem with my generator cooling fan and it ended up being the connection of the Battery Watchdog ribbon wire between the Watchdog panel and the box containing the generator controls.

Have you confirmed that you have voltage to the blower motor? If not, the next place I would look into is the Liberty Battery Watchdog system. Once you open the gray box containing containing the controls, there are a couple of small fuses that you can check. There is also a way to jumper between one of the terminals and ground which should allow the blower to work by by-passing the Watchdog controls.

In my case, I turned the watchdog off using the toggle switch and then removed the ribbon wire from the black Battery Watchdog box. After reconnection and returning the toggle switch to the "normal" position, my problem was solved. The predominate theory is that my ribbon wire connection had some how become either loose or slightly corroded.

Hopefully your fix will be as simple.

Bill Dougherty at Liberty Coach in Chicago talked me through this while I was working on diagnosing this problem and he knew my bus as if he had just put it together. It wouldn't hurt to give him a call.

[ajducote]

I doubt this is your problem, but it may be the "start capacitor" for the fan motor. That is what was wrong with mine when the fan stopped working. My "start capacitor" went bad, looking at it, I could not see a problem. Once I compared it to the new one, I could see that it was just slightly swollen. I replaced it and the fan started right up.

[phorner]

Here's a link to the post regarding my generator blower problem:

http://forum.prevostownersgroup.com/showthread.php?5556-When-your-Liberty-battery-WatchDog-has-a-hiccup-.....

[truk4u]

Richard,

Any chance the gator you hit caused damage to the squirrel cage motor by hitting the screen in the floor?

[Richard Barnes]

Richard,

Any chance the gator you hit caused damage to the squirrel cage motor by hitting the screen in the floor?

I don't know Tom but will look this afternoon. Thanks for the suggestion.

[Jon Wehrenberg]

If the generatator is run without the baffle, the heated exhaust air recirculates and the blower motor thermal overload protection whill shut down the blower motor. If the baffle has been missing for a long time and the blower motor has been cycling on the thermal overload there is a possibility the thermal oveload has failed in the open position. It was not designed to be the on-off switch so multiple on-off cycles could damage it.

I am not saying that is the issue, but it is one of the potential problems that should be investigated. The baffle is a critical part of the generator cooling system.

[gmcbuffalo]

Richard I was having a problem with the fan not stay on and I end up replacing the motor that turns the squirrel cage. I would overheat and shut down.

[merle&louise]

Someone told me that I can test my generator water pump by removing the thermostat and running the generator with the radiator cap off to see if the water is "flowing" at a good rate.

I did that today and the water in the radiator was not moving!

Is there anything else besides a water pump that could be causing this?

I priced a water pump for a Yanmar diesel engine - $446

The generator is a 20 KW Kohler.

[Jon Wehrenberg]

Tuga,

Why would you be concerned? Is the engine overheating?

If the engine is overheating I would make sure the belt to both the pump and radiator fan is intact. Assuming everything you check visually is OK I would run the engine and feel hoses for heat. The top radiator hose would be the heated water. If the engine starts showing an over temp and no heated coolant is flowing into the radiator my next step would be to verify the thermostat is opening. Removing it and placing it in water being heated and observing its temp at which is opens is all that is necessary.

If all else checks out then I would focus on the water pump. In my experience they leak but do not fail to pump unless the impellor has broken or separated from the shaft.

Before I sent my money to Kohler, I would take the pump to a local tractor dealer to see if they could match it. Yanmar engines are used on a lot of smaller diesel tractors and mowers.

[phorner]

Tuga,

I agree with Jon. You should be able by feeling the inlet and outlet hoses whether coolant is flowing through the radiator.

Although I've never tried it, I'm not sure you can "see" coolant "flowing". In my experience, when the coolant is heated and you open the cap, it just pours out under pressure from being hot.

What has "changed" that makes you want to explore your generator cooling system?

[merle&louise]

Jon & Paul,

The generator overheats (runs at 220 degrees) with 95 degree ambient temps. I tested the thermostat in a pot of boiling water - it opened. I installed a new one (after I tested it in a pot of boiling water) just to make sure. I removed the radiator and had it rodded and cleaned (twice). I flushed the system with Prestone Flush and rinsed it out thoroughly with water and filled with fresh 50/50 mixed.

I then brought it to Gulf South Armature (a generator repair shop) they removed the thermostat and ran the gen and watched for water flow - the water flowed strong. This was in May of this year.

I did the same test they did yesterday because I noticed higher operating temps. This is why I believe the water pump impella is shot.

I will check the hose temperatures with a IR thermometer today.

I will add one more observation: the operating temps increase steadily as the day goes on. As ambient temps rise so does the operating temp of the generator until it hits 225 and I shut it down. I NEVER see the temp gauge drop from the thermostat opening. This is why I feel that the water pump is not moving the water thru the system. Also, I can not see strong water flow in the neck of the radiator: only bubbles and still water.

[phorner]

Tuga,

I can only think of three reasons why coolant would fail to flow through your system: a stuck thermostat, a blockage of some sort (collapsed hose, air pocket, or such) or a water pump that has failed.

Was your generator running hot before you took it to the shop where they saw the coolant flowing freely? If they demonstrated that your coolant was flowing, and it still was running hot, there may be something else going on.

[Jon Wehrenberg]

An air bubble will stop a pump from working. Unless the system has been opened and drained since the time it worked properly that is likely not the issue, but don't rule it out. Our generators are notoriously hard to burp.

If you feel it is the water pump the easiest way, based on what you have done so far is to pull the pump and examine it. If the impeller is damaged or is slipping on the shaft it will be readily apparent. But if the impeller is OK and not slipping on the shaft then the system has blockage. The generator should cycle at the opening and closing temperatures of the thermostat and I seriously doubt that temp is 220.

If there is blockage, possibly due to a hose that has its inner plies separated and blocking flow it is possibly on the suction side. Hoses are cheap and unless they are brand new it might be good to just replace them before you pull the water pump. In that way you won't have to try to get a new gasket or face possible leakage around the pump, and you will have ruled out blockage.

[RussWhite]

Tuga,

This is NOT a recommendation, just a mention of what I do. As Jon says, air in the coolant system is a very bad thing. I have a couple cars with radiators in the front and engines in the middle - now that is a challenge to do a coolant fill and get all the air out. There are bleed screws all over the place and the directions for bleeding runs many steps long. I got frustrated with it and especially the first few trips after a fill as I was on pins and needles wondering if I got all the air out. Well, I bit the bullet and purchased a vacuum fill system and LOVE it. As you might guess, you just hook up to the fill opening with a modified cap, and after draining, start the vacuum pump. I vacuum down to about minus 26 inches of water, I think. I then let it sit there for a while as a leak check of the system and any hoses and clamps that I might have replaced or disturbed. If all is well, just slowly open the valve to the fill container and watch the coolant rush into the engine without spilling a drop! And no more worries about there being any air in there. Has worked like a charm for me. Russ

[Jon Wehrenberg]

Like Russ I also have a vacuum fill device. I have used on all sorts of vehicles that are diffiult to fill and it works like a charm.

On a recent generator coolant change I used it and never had to burp the system. The first time you use it it is kind of unsettling to watch all the coolant hoses get sucked flat.

[merle&louise]

I ran the generator this afternoon for 2 hours. Outdoor temperature was 95 degrees. Drawing 40 amps on Leg 1 and 35 amps on Leg 2. After the first hour a little antifreeze overflowed thru the tube that runs down from the neck of the radiator cap.

Using my trusty IR thermometer I shot some readings on the radiator hoses. I don't know which hose is the suction hose and which one is the return hose. Keep in mind the VDO gauge on the dash showed 200 degrees and did not move. There is no thermostat in the system; I removed it to see if the water was flowing.

The top hose - leads from thermostat to the top of the radiator - 170 degrees

The bottom hose - leads from the water pump to the bottom of the radiator - 160 degrees

I spoke to a mechanic with Gulf South Armature and he said it sounds like a bad water pump. I asked him about burping the generator and he said all he ever does is let it run with the cap loose adding water/antifreeze as needed.

Why does the VDO gauge read 200 degrees if the hoses are showing 170 - 160 ???

[Jon Wehrenberg]

It may be an error in calibration. I presume the generator system has an automatic shutdown i the event of an over temperature condition. The fact your gauge read 220 plus degrees but the generator did not shut down suggests the gauge is wrong. It would be interesting to take the temps at the temperature sensor that is a part of the automatic shut down.

However, if there is no thermostat I would expect lower temperatures. That is solely a guess so take the comment with a grain of salt. You did not have a big load on it. Assuming there is a correlation between the VDO gauge and the temp at the radiator it does seem when it waqs reading 220 at the VDO the outlet from the engine (top hose) was at 190, and that sure is not a concern, and the bottom likely was 180, something I think is too high. I would expect a greater than 10 degree temperature differential from inlet to outlet on the radiator. I also shooting from the lip on that comment and now my curiosity is going to get me to shoot some temps on mine to see just how much a radiator drops the temps.

[phorner]

I tend to agree that there should be more than a 10 degree drop in temperature through the radiator.

On mine, with the generator up to operating temperature (180), my top radiator hose is too hot to hold onto, while the bottom hose is almost cool... you can easily hold your hand on the copper pipe comfortably. In fact, mine was cooling so well I suspected a problem at first.

[johnklopp]

Most liquid heat exchangers are designed for a 10 F degree drop at full load. The temperature drop will increase at light load due to the reduced flow caused by the modulating thermostat. The design point of all heat exchangers is the approach temperature which is a measurement of the difference between the outlet water temperature and the inlet air temperature acros the heat exchanger. Typical design conditions represent an approach temperature of 40 degrees F.

An impeller that has lost its vanes is rather unlikely. The most probable problem in my opinion was pointed out by Jon as a collapsed hose on the suction side of the pump. The suction hoses typically have a spring on the inside of the hose to prevent collapse when the engine cools and the water volume is reduced.

You should be able to determine if you have circulation and heat transfer by using your infrared thermometer If you don’t have one, you should, how else can you check your tires on those short rest stops?

[Jon Wehrenberg]

JUst as a point of information on some data that I do know, I observed my bus engine thermostat operate on a return trip from New Orleans this spring.

My thermostatic fan clutch had acted up so I had locked the fan. Prior to that my fan clutch controlled engine coolant temps and the temps would cycle between 200 and 205 as indicated on the gauge.. With only the engine thermostat to control engine temps the engine cycled between 190 and 195 as indicated by the gauge.

For the entire trip, including those portions where the bus was pulling hills and was operating at max power the thermostat cycled open and closed. This was consistent with the operation when the fan clutch was working normal, although the cycle temps when using the fan clutch were between 200 degrees indicated which I assume was when the fan clutch disengaged, and 210 under hill climb conditions which was when both clutch speeds were engaged. My point is that as long as a fan is fully engaged an engine is likely to cycle its engine coolant flow via the thermostat. With the thermostat removed as in Tuga's coach I would have expected to see temperatures in the 140 to 160 range at the radiator inlet side and lower at the suction side.

The reason I suggest they should be this low is because the cooling system is working with a generator that is lightly loaded and the system design should be capable of handling excessive ambient temps under full or heavy loads. I am having a problem agreeing with John on the 10 degree temperature drop, but until I can determine that is typical I have to accept his word because I doubt if any one else in the Prevost universe has a better understanding of the transfer of heat.

[phorner]

Jon,

I am sure that my generator radiator cools more than 10 degrees from inlet to outlet. When I get a chance, I'll run mine today (should be in the 90's here in Florida) under load and measure the actual temperature at inlet copper pipe and outlet copper pipe.

Last time I checked, the inlet pipe was too hot to hold yet the outlet pipe was not a problem at all. I was quite surprised.

[phorner]

Tuga,

For what it's worth, here are the operating stats from my generator this noon:

Generator running for 1 hour under load of 4 CruiseAir units plus whatever else was on, approximately 35 amps/leg.

Outside ambient temperature 91 degrees

Dash analog gauge reading 175 degrees

Top radiator tank is 157 degrees via IR thermometer (inlet copper piping too hot to hold)

Bottom radiator tank is 109 degrees via IR thermometer (outlet copper piping warm to touch, can hold without discomfort)

My radiator appears to provide nearly 50 degrees of cooling WITH the blower operating properly.

I don't know how much these numbers might change if I ran the generator all day or while under way on the highway.

Hope this helps some....

[phorner]

As an aside, it sure appears that the long run of copper coolant lines between the generator and the radiator provides for significant cooling, at least while parked...

[Jon Wehrenberg]

Those are numbers consistent with what my gut told me to expect. The spread between inlet and outlet temps through the radiator (heat exchanger) is going to be significantly impacted by ambient temps. If the OAT is lower than 90 then the difference between the OAT and the thermostatically maintained inlet temperature is going to be greater and thus the radiator outlet temps are going to be even lower. That in turn will result in greater periods of generator operation with the thermostat closed as a means of the generator operating at the desired temperature.

[merle&louise]

Tuga,

For what it's worth, here are the operating stats from my generator this noon:

Generator running for 1 hour under load of 4 CruiseAir units plus whatever else was on, approximately 35 amps/leg.

Outside ambient temperature 91 degrees

Dash analog gauge reading 175 degrees

Top radiator tank is 157 degrees via IR thermometer (inlet copper piping too hot to hold)

Bottom radiator tank is 109 degrees via IR thermometer (outlet copper piping warm to touch, can hold without discomfort)

My radiator appears to provide nearly 50 degrees of cooling WITH the blower operating properly.

I don't know how much these numbers might change if I ran the generator all day or while under way on the highway.

Hope this helps some....

Paul,

Thanks for running the "test" - I feel that the 50 difference you experienced is telling me that my system is either blocked or my water is not working.

Jon & John,

Thanks for your explanations and advice. I am going to remove my water pump and have a look at the impeller. I am also going to change the hoses.

[phorner]

Tuga,

I agree with Jon that you have nothing to lose by changing the hoses first and see if that corrects your problem.

Just might save you a lot of work....

[johnklopp]

I think everyone has presented excellent points taking into account the actual operation they are experiencing at that time. No one has presented opinions and data that I am in disagreement with.

Please note the following comments on various typical design conditions..

Temperature drop at full load is a design condition that will never be seen with normal operation. Heat exchangers are always going to be designed for the worst case you can imagine. The air temperature for a worst case design will likely be 20 degrees above the hottest day any place in the country. The extra 20 degrees of air temperature is due to heat radiated off the black pavement. This would suggest an entering temperature of approximately 150 degrees F.

The heat rejection of the engine is also rated at a higher amount than a properly operating engine will produce. Diesel engines are readily capable of exceeding maximum power ratings and heat rejection by nothing more than an improperly adjusted governor. Your 17.5Kw generator is probably capable of putting out close to 20Kw for a period of time without problems. This additional heat rejection is part of the full load design the engineer will use to select the heat exchanger, coolant flow rates and air flow rates for the system.

All fluids have a design standard called specific heat that is used to define the amount of energy or heat that can be transferred by a quantity of fluid. A fluid is either a liquid or a gas. Both use the same basic approach for calculating heat transfer. Air at sea level is equal to 1 and water is equal to 1. All of you pilots know how much the density of air changes as you go up in altitude. You will very quickly get to the point that you need to double the mass flow or volume of air to have the same heat transfer. Coolant has the same problem, you add antifreeze to increase the boiling point but it also reduces heat transfer at the same time. Your system was designed to have a 50/50 mix of antifreeze and water. One day your system is low so you just add undiluted antifreeze. Great, it won’t freeze now till you’re at 40 degrees below zero or some other temperature based on the dilution. But how many of you know that the additional antifreeze now requires you to move additional coolant thru the system to have the same heat transfer? Does anyone use a hydrometer to see what the coolant mix is?

The approach temperature differential between the leaving water temperature and the entering air temperature will be affected by a fouling factor caused by contaminants in the coolant and the cleanliness of the heat exchanger and the engine itself. The design engineer will take into account a moderate amount of fouling in his calculations. If a technician knows what the approach temperature is on a clean heat exchanger, heat can determine when a heat exchanger needs to be rodded out to return the heat transfer capability.

At anything less than full load, the coolant flow will be reduced causing the coolant to spend additional time in the heat exchanger. A greater temperature drop will take place due to the additional time the coolant spends in the heat exchanger.

[phorner]

John,

Thanks for the great post! Always informative and educational.

Your discussion regarding the design considerations reminds me a lot of some of the things we addressed while designing highways such as impact factors for bridges rather than just support of a static load and design vehicle speeds in considerable excess of posted speed limits when designing curve radii and superelevation.

[merle&louise]

Well I found the problem of why my generator was running hot!

Bad water pump! Installed the new water pump and the water in the radiator is running like a spotted a$$ ape!

It ran for 4 hours today in 95 degree heat with a full load and the operating temp was 180 degrees.

Problem solved; thanks to all who contributed.

Life is good when your generator runs cool!

[phorner]

Well that's great news, Tuga!

Glad to hear you got to the bottom of it and you're back to keeping your cool...:D

[Jon Wehrenberg]

Tuga,

Do you know what was wrong with the pump? Impellor slipping? Broken vanes on impellor? Cause of the failure? A lot of us have the same generator and if we can learn from this it would be helpful.

[merle&louise]

Jon,

From what I can tell the pump impeller did not have any broken blades and the blades would turn as the shaft was turned. It was of course dirty inside; looks like rust and antifreeze "gook" may have blocked inside the pump itself.

We removed the radiator in order to get to the water pump, so while it was out I hosed it out until the water going thru it was clear. I also turned the radiator upside down and removed some more water that had accumulated in the bottom.

We installed the new pump and ran it with pure water to see if the water would move (we removed the thermostat to do the test). We had good strong water flow in the neck of the radiator so we drained the water and re-filled with 50/50 pre mixed Prestone antifreeze.

I would say that removing the radiator and washing it out is good preventive maintenance. I plan to do it every 2 years when I change my antifreeze. Turning the radiator upside down and draining excess water thru the neck is key IMO. This should be done a few times to get all the gook out.

Sure is a good feeling to have the generator running at normal operating temp.

[Jon Wehrenberg]

Is it possible the pump was not defective, but perhaps had blockage combined with blockage in the radiator?

A pump going bad is kind of rare unless it is somehow physically damaged.

[phorner]

Is it possible the pump was not defective, but perhaps had blockage combined with blockage in the radiator?

A pump going bad is kind of rare unless it is somehow physically damaged.

Usually, when a water pump fails, it leaks and/or you can feel the play in the impeller shaft due to the bearings failing.

[Jon Wehrenberg]

But even if it is leaking it still moves a lot of water. I consider leaking age related, but if it is not leaking but fails to pump there is a defect that needs to be identified and corrected. I'm guessing the coolant on our generators can have the same issues as our engines and dropout has to be considered.