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Electric Cooling Fan HI/LO RPM
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=92900		 Page 1 of 1
Author:  seafish [ Sat Mar 30, 2024 12:14 am ]
Post subject:  Electric Cooling Fan HI/LO RPM
Today I was checking the operation of the electric cooling fan on my 2005 KJ CRD

By using a handheld tachometer and jumping terminals 87 and 30 on each of the High speed and Low speed fan relays, I was able to ascertain that for some reason there is NO fan speed difference when jumping the relays.

On other words, when jumping EITHER relay, the fan turned on and ran at 2000 RPM.

Of course, I was expecting the fan to run at different speeds depending on which relay I jumped, but that was NOT the case. Pics below.

The question is WHY??

Is 2000 RPM the normal HIGH speed or is it the normal Low speed?

Anybody have an idea??

Image

Image
Author:  DieselJeepLuvr [ Sat Mar 30, 2024 1:35 am ]
Post subject:  Re: Electric Cooling Fan HI/LO RPM
Check the voltages going to the fan at the different settings.
Author:  WWDiesel [ Sat Mar 30, 2024 9:33 am ]
Post subject:  Re: Electric Cooling Fan HI/LO RPM
This system has never made a lot of sense to me. If you pull either one of the relays, high or low speed, the ECM will energize the single relay still in place and the fan will run. Not sure why this is as the wiring diagrams does not provide any answers.

Just a wild guess!
Without testing on my own, it may require both relays energized at the same time to get high speed and either one of the relays singularity to get low speed? :?
Author:  seafish [ Sat Mar 30, 2024 10:08 am ]
Post subject:  Re: Electric Cooling Fan HI/LO RPM
DieselJeepLuvr wrote:
Check the voltages going to the fan at the different settings.


Will do that today and post back.
Author:  seafish [ Sat Mar 30, 2024 10:26 am ]
Post subject:  Re: Electric Cooling Fan HI/LO RPM
WWDiesel wrote:
This system has never made a lot of sense to me. If you pull either one of the relays, high or low speed, the ECM will energize the single relay still in place and the fan will run. Not sure why this is as the wiring diagrams does not provide any answers.

Just a wild guess!
Without testing on my own, it may require both relays energized at the same time to get high speed and either one of the relays singularity to get low speed? :?



Interesting...if the fan is rated for 24v and if the relays to the fan are wired in SERIES, but then again how would that make sense since the Jeep has only ONE 12v battery powering BOTH relays.

Or perhaps the fan motor has TWO windings and each relay energizes one of them. I think that this is more likely!

I will disconnect the fan and try energizing the relays individually and combined while checking the voltage at the fan connector...

Still, this is a little hard for me to wrap my brain around,,,MAYBE that is why there is a 3 pin connector for this fan?

I know you said that the fan wiring diagram doesn't show anything decisively, but do you have a link to the wiring diagram??

TIA
Author:  WWDiesel [ Sat Mar 30, 2024 10:34 am ]
Post subject:  Re: Electric Cooling Fan HI/LO RPM
Jeep online manuals:> https://www.colorado4wheel.com/manuals/Jeep/KJ/

See 2005JeepKJServiceManual.pdf, section 8W for wiring diagrams.

This is my custom drawn cooling fan wiring diagram showing all components.

Image
Author:  seafish [ Sat Mar 30, 2024 10:39 am ]
Post subject:  Re: Electric Cooling Fan HI/LO RPM
WWDiesel wrote:
Jeep online manuals:> https://www.colorado4wheel.com/manuals/Jeep/KJ/

See 2005JeepKJServiceManual.pdf, section 8W for wiring diagrams.

This is my custom drawn cooling fan wiring diagram showing all components.

Image


EXCELLENT, thank you !!!

I will print a copy bring it with me when I check the relay voltages again today
Author:  seafish [ Sat Mar 30, 2024 9:25 pm ]
Post subject:  Re: Electric Cooling Fan HI/LO RPM
WWDiesel wrote:
This system has never made a lot of sense to me. If you pull either one of the relays, high or low speed, the ECM will energize the single relay still in place and the fan will run. Not sure why this is as the wiring diagrams does not provide any answers.

Just a wild guess!
Without testing on my own, it may require both relays energized at the same time to get high speed and either one of the relays singularity to get low speed? :?



Winner, winner, chicken dinner !!!

After staring at your excellent fan wiring diagram, I decided that eihter the relays are wired in series OR that the fan motor has TWO sets of windings , one relay powering each winding.

NOT sure which it is yet, and leaning towards the latter, but by energizing BOTH relays at the same time, (NOTHING blew up ...another WIN!!!) the fan started spinning at 2400 RPM instead of just 2000.

Pics or it didnt happen --

Image
Author:  user113 [ Sun Apr 07, 2024 11:25 pm ]
Post subject:  Re: Electric Cooling Fan HI/LO RPM
Good find. The problem with these Jeeps is that there are so "black-box" modules with very little indication of what they're doing, so looking at the wiring diagrams almost always inadequate, and in many cases the descriptive text is also insufficient.
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