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Old 09-24-2020, 08:41 AM   #1
Mini-Skoolie
 
Join Date: Jul 2020
Location: Ohio
Posts: 21
Year: 2003
Coachwork: Blue Bird
Chassis: All American RE
Engine: Cummins 8.3L ISC - 315HP
Rated Cap: Lots of kids.
Hydraulic oil cooling fan problems.

Hey everyone, I was hoping some of you more knowledgeable folks could help me with an issue going on with my hydraulic oil cooling fan. Electrical stuff is definitely not my strong point, so I could use some guidance.

I have a 2003 Bluebird All American RE (8.3L) and on my transit home from picking the bus up I would occasionally get a high temperature warning light for hydraulic oil, causing me to either reduce speed or pull over for a few minutes to let the hydraulic oil cool down.

After getting it home, I ripped the old hydraulic cooling fan out and it was in rough shape; the fan was completely seized up and would not spin. I retrofitted the area and replaced it with a 12” aftermarket cooling fan jobber using the existing wiring for the old fan. I tested the fan before hooking it up and the fan itself definitely works.

The issue I am having is the fan is still not kicking on, which in my mind could be one of two things: 1.) the hydraulic oil hasn’t gotten hot enough for it to energize the fan since I’ve gotten it home, or 2.) something is funky with the wiring to the fan.

Here are some things I’ve done:
- I checked the hydraulic oil cooling fan fuse and it doesn’t look blown to me.

- I bought a BlueFire plug to sync up to my phone to monitor hydraulic oil temperature. However, I am still learning with this App and I haven’t been able to find an option to show that reading anywhere. I’m not sure if I can add that in or what.. That reading isn’t in the set of “gauge” options for display. I have used a kitchen infrared temperature gun to look at external temperatures of various hydraulic components (reservoir, oil cooler, etc.) and the external temperature was hovering around where the cooling fan should be energizing (160*F). Again, these are external temperatures and I’m not sure what the actual sensor is reading, but it is the best thing I had at the moment.

- When I think the hydraulic temperature is at the level where the cooling fan should be kicking on I have used a multimeter to check the voltage of the wires the fan is connected to. I got a super low reading (like 0.2V DC). I’m not sure what that means, other than I know it should be ~12V to energize the fan.

Using https://www.centralstatesbus.com/wp-...s/a3hydfan.pdf as a troubleshooting guide (pg 10) I need to “Check for 12 volt on number 30 pin of the Hayden fan cooler” and “Jumper between terminal 30 and 87 of the fan relay”. I’m just not sure where those are located. I’ve tried tracing the wires back from the cooling fan but I eventually lose them in a spot that is hard to crawl through and obscured but other components towards the rear of my bus.

I’ve also tried disconnecting the “cooling fan temperature switch” (pg 9 of guide). Because it says “Disconnect the hydraulic oil temperature sensor on connector P2, If the fan runs, the hydraulic oil sensor or the circuit is at fault”. I’m not sure if that was the right connector to unplug (not sure what connector P2 is). Either way when I disconnected it the fan still did not kick on.

I’m not too sure where to go from here and am grateful for any guidance. My last resort would be to just hook the fan up to a toggle switch I can control in the pilot house and control it manually, but I would prefer to have it automatically kick on and off in case I forget to do it.
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