Gut check - radiator fans spin at different speeds?

[honeybadger]

Howdy all. Need some help with a gut check. Prepping for my first engine start since the refresh and I was testing the radiator fans since I had some coolant temps creeping up last year. I pulled the relays and jumped the circuit and discovered that my passenger side fan runs substantially faster and moves more air than the driver side.

Relays are 89 (driver) and 91 (passenger). Anyone able to verify for me?

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[JAJ]

Howdy all. Need some help with a gut check. Prepping for my first engine start since the refresh and I was testing the radiator fans since I had some coolant temps creeping up last year. I pulled the relays and jumped the circuit and discovered that my passenger side fan runs substantially faster and moves more air than the driver side.

Relays are 89 (driver) and 91 (passenger). Anyone able to verify for me?

Hope this helps:

 

[JAJ]

The way this works is if the PCM signal LFC is active, then the two fans will be connected in series and will run at about half-speed. When HFC and LFC are both active, both fans run at full speed. When neither is active, they're stopped.

 

[honeybadger]

The way this works is if the PCM signal LFC is active, then the two fans will be connected in series and will run at about half-speed. When HFC and LFC are both active, both fans run at full speed. When neither is active, they're stopped.

Ahh, I should have looked in the manual. I'll have to look into testing that part of the system. I didn't consider the PCM would control fan speed. Doh!

Though, I am bypassing the PCM all together with this jumper and spinning each fan individually, which should be at max speed. Correct? And if that's the case, are they supposed to be spinning at wildly different speeds? Seems like it would lead to a radiator with big temperature variation across it.

 

[oldbmwfan]

Ahh, I should have looked in the manual. I'll have to look into testing that part of the system. I didn't consider the PCM would control fan speed. Doh!

Though, I am bypassing the PCM all together with this jumper and spinning each fan individually, which should be at max speed. Correct? And if that's the case, are they supposed to be spinning at wildly different speeds? Seems like it would lead to a radiator with big temperature variation across it.

Fans don't do anything on track unless you're running nose-to-tail with someone, literally inches from their bumper for multiple laps. At speed, the airflow from the front is the overwhelming cooling.

 

[galaxy]

I swapped to two 16” fans on my F150 to get the boat anchor factory mechanical fan off the front of the engine (talk about instant increase in throttle/engine response that you could feel!!). Anywho, I did a lot of testing and observation because I’m a huge nerd like the rest of us, and discovered that even towing a trailer on the hottest of day, those fans did nothing above about 30 mph. Airflow alone beyond that was aplenty. I know frontal area, radiator size, and all that comes into play, but just supporting what @oldbmwfan is saying.

 

[honeybadger]

Good feedback. I know on a previous old school race car that had a radiator fan tied to a mechanical fix, we had to remember to turn it on or the car would over heat. But that car had a lot less technology and heat in it than HB.

 

[JAJ]

...I am bypassing the PCM all together with this jumper and spinning each fan individually, which should be at max speed. Correct? And if that's the case, are they supposed to be spinning at wildly different speeds?...

The answers to your two questions are, in order, "yes" and "no". One fan seems to have a problem. That said, if you don't have to spend time idling, you can ditch the fans entirely - I spent some time driving Tom's Nascar trainers at the Ridge and they don't have fans - you stop the engine if you have to sit and wait.

 

[mustangguy88]

If your unsure if there is or isn't a issue with each fan. Try disconnecting the fan plug on the harness directly to the fans. You should be able to activate the fan motors directly and ensure no interference with the ECM or BCM.

Also, if you really want to dig into your car at depth, look at getting the dealership wiring manual in paperback, and the dealers service manual on CD, both on Ebay. I have them both for a 2015 Mustang and they gave me the confidence to do just about anything with the car. Along with FORSCAN and all their available resources.

One last tool to keep you from the dealership is a MATCO Maximus 2.0, they sell used on Ebay also for around $900.00 to $1,500.00. It will let you do complete dealer level diagnostics. It will pay for itself the first few times it keeps you from the stealership.

Hope the info helps, the above combo really let me go nuts thru my project.

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