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Topic: 91 GV side radiator fan stays on ---- FIX (Read 703 times) previous topic - next topic

91 GV side radiator fan stays on ---- FIX

The hydraulic cooling fan on my 91 GV has been running full time.  In trying to diagnose the problem I tried to get some info from the engine manufacturer (CAT) on the location of the sensor and all they would say is that the coach builder should have that info, even though the temp sensor I was trying to locate was on their engine.  I tried to get some info on the where abouts of that temp sensor from FT and of course they referred me back to the engine manufacturer.  So as far as it goes on these older machines, you have to figure it out for yourself.  I started at the hydraulic solenoid and with the aid of a tone tracer and some hand over hand work I was able to trace the wiring to a relay in the dash that was defective.  I replaced the relay and it still didn't work. (rats).  More checking reveled that when the relay went, it took the circuit fuse with it.  I replaced the fuse and (praise God) it worked again.  I firmly believe that on these older coaches, a tone tracer needs to be in every one's tool box since the schematics (if available) just are not accurate in some ways and incomplete in others.  Hope this may help some one.  ----  Have a great day  ----  Fritz
Fritz & Kathy Johnson
1991 36'

Re: 91 GV side radiator fan stays on ---- FIX

Reply #1 –
Fritz what engine do you have, mine is a 3208 cat and the bypass solenoid valve has to be powered open. Any voltage failure will result in a fail safe with fan running. I have no wiring diagram for this either. It is my belief that it runs thru a N.C. two wire sensor at about 10 O'Clock to the crank pulley.
Old Phart Phred, EIEIO
89 GV ored 36' #3405 300 hp cat 3208 ATAAC side radiator, mountain tamer exhaust brake

Re: 91 GV side radiator fan stays on ---- FIX

Reply #2 –
Our coach has the 3208T and the sensor is located as you say.  It is a larger sensor with a NO and a NC contact and the power goes thru the NC contact..  System is set up as you say to fail safe with fan running.  From what I have figured out is that the sys. consists of power from the fuse block (10 amp) in the dash to the relay in the dash, to the sensor in the block, then to the hydraulic control valve.  I'm not sure that it is bad to have the fan running all of the time, but it just makes me feel better to have things work as they were designed to work.    Have a great day  ----  Fritz
Fritz & Kathy Johnson
1991 36'

Re: 91 GV side radiator fan stays on ---- FIX

Reply #3 –
Dam. I wondered if ours was supposed to run all the time, but ya,  you start the engine cold and the fan is running. Now I need to fix that
Robert and Susan
 1995 36' 280 WTBI 8.3 3060r
 1200 watts on the roof, 720 Ah of lithium's
 Build # 4637. Motorcade # 17599
        FMCA  # 451505
        18  Wrangler JLUR

Re: 91 GV side radiator fan stays on ---- FIX

Reply #4 –
Quote from: Bob & Sue –
Dam. I wondered if ours was supposed to run all the time, but ya,  you start the engine cold and the fan is running. Now I need to fix that
Do not know for sure about your coach, but some have the hyd fan turning at low speed whenever engine is running. And will ramp up with engine temps.
Jim C.
coachfree, previous 1997, 1999, 2000, and 2003 Foretravels.

Re: 91 GV side radiator fan stays on ---- FIX

Reply #5 –
Just for info  ----  The speed of the fan motor is directly related to the RPM of the engine.  If the system has failed and the fan runs all of the time, it will run slowly at idle and increase in speed as the RPMs increase.  From my home work and trouble shooting on my rig, the fan should turn on at approx. 200 deg.  and when the engine has cooled to approx. 180 deg, the fan should trip off.  It is an on--off system, I have not seen any indication of a sys where the speed is determined by temperature.  Have a great day  ----  Fritz
Fritz & Kathy Johnson
1991 36'

Re: 91 GV side radiator fan stays on ---- FIX

Reply #6 –
I believe on the 300 hp models it's required to run for the charge air cooler
Old Phart Phred, EIEIO
89 GV ored 36' #3405 300 hp cat 3208 ATAAC side radiator, mountain tamer exhaust brake

Re: 91 GV side radiator fan stays on ---- FIX

Reply #7 –
Quote from: fkjohns6083 –
Just for info  ----  The speed of the fan motor is directly related to the RPM of the engine.  If the system has failed and the fan runs all of the time, it will run slowly at idle and increase in speed as the RPMs increase.  From my home work and trouble shooting on my rig, the fan should turn on at approx. 200 deg.  and when the engine has cooled to approx. 180 deg, the fan should trip off.  It is an on--off system, I have not seen any indication of a sys where the speed is determined by temperature.  Have a great day  ----  Fritz
Agree with Phred.
Of course the faster the engine turns, the faster the hyd fan motor will turn. But in my coaches, the valve on the discharge of the hyd pump allows some flow to the fan motor at low temperature and low engine speed.  Believe this is so the manifold air passing through the intercooler has some heat transfer, and when the ecm, or perhaps in other models, a wax element or other method, sees high cooling water temps,  allows full flow from the hyd pump to the fan motor. More of a low speed or high speed operation, but both relevant to hyd pump speed. Of course if you do not have an intercooler that requires flow over it at all times, probably not necessary for low fan motor speed at all. Non intercooled engines would only need an on or off, based on water temps.
Have heard of engines that actually vary fan speeds proportionally to engine temps.
Jim C.
coachfree, previous 1997, 1999, 2000, and 2003 Foretravels.

Re: 91 GV side radiator fan stays on ---- FIX

Reply #8 –
If you make the bypass small enough the fan would run on slow but I think you still use the same amount of energy
Old Phart Phred, EIEIO
89 GV ored 36' #3405 300 hp cat 3208 ATAAC side radiator, mountain tamer exhaust brake

Re: 91 GV side radiator fan stays on ---- FIX

Reply #9 –
Cannot say about variable speed loads, but  do know in engines with constant speed hyd pumps, governor load settings will be low,  [low loading] on bypass, and high, on high loading, [or max load on hyd motors]. eg: 100 hp on bypass, 500 hp on full hyd load.
https://www.rvtechlibrary.com/engine/Cat_RV_Performance.pdf
Think Brett Wolfe helped write this one.  Read the part about engine fan hp.
Jim C.
coachfree, previous 1997, 1999, 2000, and 2003 Foretravels.

Re: 91 GV side radiator fan stays on ---- FIX

Reply #10 –
Yes, I have seen that article and I a take with a big grain of salt, I have a fan simulation program that I have run thru various scenarios, and given my diameter fan I haven't been able to exceed 7.5 hp at 115 db. You can say the fan blade efficiency is low, but that generates a lot more noise which I can't recreate. You can say it's the blade pitch but you can only go so far before blades stalls and vibrates and gets very loud also. Can my drive belt setup transfer 7.5 hp not including my air compressor chewing up 2-3 hp producing 12 scfm, doubtful. BTW somewhere in my Oshkosh manual it states IRC the fan starts spinning when engine temp hit 40 F. Will have to look as this seems rediculous, maybe 40 C.
Old Phart Phred, EIEIO
89 GV ored 36' #3405 300 hp cat 3208 ATAAC side radiator, mountain tamer exhaust brake

Re: 91 GV side radiator fan stays on ---- FIX

Reply #11 –
Prevost predicts strong 2018 with new equipment, services - Bus & Motorcoach...
ELECTRIFYING THE FUTURE AT PREVOST | Prevost
Prevost is claiming they gain 75 hp by eliminating the mechanical radiator fan, but can only imagine how big the alternator has to be to run all those electric fans,
Jim C.
coachfree, previous 1997, 1999, 2000, and 2003 Foretravels.