[mycbarnes]

Under my coach, in front of the differential is a heat exchanger unit for the radiator fan hydraulic fluid. Mine has 2 electric cooling fans. Are these fans supposed to be always powered on, or temperature controlled by fluid sensor and relay? This heat exchanger is not for my dash air, that condenser is mounted more forward. The exchanger I am asking about is not the transmission fluid cooler, but solely for the radiator fan motor hydraulic fluid. Any help would be appreciated.

[Georgeb]

I thought that fan/cooler was for transmission
Guys at Newell said it would run as needed

[Richard]

That cooler is for the hydraulic system not the tranny. The first Newell I owned th fans were
On all the time. The second one only comes on the when needed.

[RussWhite]

Richard is correct. Coach 530 on thermostat.

[mycbarnes]

Thanks, mine does not come on in the engine run position and confirmed with voltmeter no power at the fans. I did apply 12v with a battery to the fans directly and they work. I could not find a temperature sensor in the hydraulic reservoir, the pump or radiator fan motor, the Vickers solenoid body that controls the radiator fan, nor the heat exchanger itself. Which is why I was asking what others had experienced and it was bugging me not seeing the heat exchanger 12v fans working. Now thinking the DDEC computer controls the heat exchanger fans when the radiator fan is in the run position. But I haven't run it long enough to get radiator fan to kick in. There has to be a relay set for the heat exchanger fans, but not sure yet where. Probably in engine bay cabinet, but it isn't marked. No fuse found either, maybe a auto reset headlight circuit breaker can type instead. Once I figure out how it is wired I'll post a note. It's bound to help somebody who doesn't have working fans at all to troubleshoot.

[House Divided]

Terry, on my '96 the Hayden hydraulic system electric cooling fans are controlled by a thermal switch threaded into the back of the hydraulic oil reservoir located above the engine bay electrical panels. Power to the electric fans is pulled from a source in the engine bay panel that switches on with the ignition key - so power is available with the key on, but the fans run only if the temperature switch closes - I think around 160 degrees fluid temp. 

I wish I remembered more detail on power source, but I am not near the coach. I do remember it was labeled in the electrical cabinet. When my temp switch failed, all I had to do was bypass that temp switch to get the fans to come on and off with the ignition.

Hope this helps!

[mycbarnes]

Thank you David for the information. I'll look at the reservoir  again for a temp sensor, as that makes the best place to capture a reading. The system is very important to have operating and with the location of the heat exchanger buried under the coach, it's something everyone should be aware of working and if it isn't, it's a silent killer as there is no dash warning or parameter in vmspc. If the hydraulic fluid gets too hot, it will get thinner, the hydraulic pump could gall and fail. Same for the hydraulic motor that runs the radiator fan. The failure of the heat exchanger for the fluid could chain react to a failure of the radiator fan system. Then, well, even worse. I just got our coach in May, I have been getting it ready for our first adventure from Tx to Airventure in Oshkosh. First day on road I am going to see blistering Tx heat. Trying to think of all the systems to check before hand.

[House Divided]

The temp switch should be in what I consider the back of the hydraulic oil reservoir- accessed from the passenger side engine compartment door, up and to the left.

My reservoir has three ports - one for a dash indicator light, the dash temperature gauge, and the temp switch.

[Latitude 28]

Sure enough, just looked at my hydraulic reservoir. Have the level switch and a temp switch on the front, inboard lower corner. Never had noticed it before nor paid any attention to the tank.....now I know what they are for....thanks!

Steve

[mycbarnes]

Worked on coach some yesterday, my reservoir doesn't have any electrical going to it or any threaded bosses for a sensor. Could not find any electrical hookups at pump, motor or control valve other than 2 wires for solenoid on Vickers control valve. After finishing oil change today I will run coach long enough to get radiator fan to cycle on. Then see if 12v heat exchanger fans come on. If not I'll start ringing out wires and see why fans don't come on. Appears Newell changed how the cooling for the hydraulic fluid operates close to the time between David's and I's serial numbers. There is an unmarked relay and a auto reset can type circuit breaker that is in rear engine bay panel. It gets it's power from a short wire to dash power contactor. If this turns out to be the relay for exchanger fans, I'll take a picture and post. Thanks for everyone's help so far. This is actually a good topic for everyone to know how their system operates.