Radiator fan not coming on.

BenKenobi · Jul 3, 2017

It was the "sub fan" fuse. Second 30A fuse from the left (above #13 in the diagram you posted)

I do have low and high speed fans now, and when I cut on the A/C both fans kick in on high. It looks like before, I had just a high speed condenser fan.

I took a screenshot of the graph of the coolant temp sensor:

Looks like it cuts on at 208 and off at 197 if one assumes that's 98 and 92 celsius.

As far as why the fuse blew -- that's definitely a mystery rattling around in my head. Maybe just a defective fuse that finally had enough? I guess I'll keep an eye on it and if I pop another fuse there, then I'll dig further.

John Clark · Jul 4, 2017

So, that's fuse #30 which is the condenser fan fuse. I can see how a blown #30 fuse would prevent low speed on both fans. What I don't understand is how that fuse would affect high speed on the radiator fan. The diagram I posted is the factory Honda diagram so either the diagram is incorrect or your symptom description wasn't fully correct. There's no way, according to that diagram, that a blown #30 should affect the radiator fan high speed circuit.

Below is the diagram from the factory service manual which, while drawn differently, is the same. It makes me wonder if the drawings are wrong or the fuse box was built wrong and that fuse 29 is wired downstream, in series, with fuse 30 when it should be in parallel.

Would you mind doing me a favor? With the key off, pull both fuse 29 and 30 and see if fuse 29 still has 12 volts on one side of it. I'm curious to know if you pull fuse 30 if it depowers fuse 29. It shouldn't but according to your symptoms it does.

John Clark · Jul 4, 2017

It also doesn't make sense that the condenser fan fuse could be blown and yet the condenser fan was still running on high speed. Just to be clear, the fan that wasn't working was on the driver's side, correct?

John Clark · Jul 4, 2017

You can disregard the fuse checking. Neither fan would work if an upstream fuse blew.

In looking at it closer there are two possible reasons for the discrepancy. Either someone has swapped the connectors going to your fans (vehicle was in an accident possibly or just plugged them in backwards) or the diagrams are labeled backwards on the drawings. We never confirmed any wire colors going to the fan. What color wires are going to the fans? The driver's side fan should have a blue and a black. The passenger side fan should be a pink and a brown (or red on the fan side of the connector.) If I swap the labels on the drawings (or swap the connectors on your vehicle) then that fuse blowing would give the exact symptoms you had.

It wouldn't be the first time a diagram was wrong...doesn't help in tracing circuits!

BenKenobi · Jul 4, 2017

There was a front-end collision noted on the carfax... but yeah the fact that the sub fan fuse was the problem makes me really want to figure out why it was the problem. Sometime in the near future, I may take a look at wire colors, pull the sub fan fuse (to replicate the conditions) and see. Maybe I was having a brain fart and I actually replaced the main fan fuse and my brain rewrote the story on me. I'm 99% sure it was the sub fan fuse, because I even looked at it on the diagram and remember thinking to myself "sub fan? I thought that was the condenser." ... Right now, I'm just happy it's keeping things within operating temperature regardless of how it's wired up.

...and yes -- driver's side fan was the malfunctioning one.

John Clark · Jul 4, 2017

The "Sub fan" is the condenser fan fuse. See the fuse panel diagram:

http://www.revbase.com/BBBMotor/Wd/DownloadPdf?id=1008509

According to the component locator diagram in the service manual the "radiator fan" is on the driver's side and the "condenser fan" is on the passenger side but your symptoms and solution only make sense if the radiator fan is the passenger side fan and the condenser fan is the driver's side fan. It's really odd.

191145 · Jul 4, 2017

Yes, I wanted to know if the engine was overheating (IOW, most of us just drive the car and check the temp gauge every so often - if it starts running hot, then we look for causes - I thought maybe you were sort of 'putting the cart before the horse' by looking for the fan to run when it was not being called to run by the circuit, hence the question) and my definition of that is movement of the gauge beyond its usual position as well as other typical overheating symptoms. Glad you found the fuse but like the others now I wonder what blew a 30 Amp fuse? With past front end damage the possibilities are many but I would try to find a short caused by a 'skinned' wire in contact with metal. I guess you'll know that you have a short if the fuse goes out again.

Squiggtrust · Jul 30, 2019

Hello im having a similar issue my radiator fan works on low speed when car is not to hot if i turn on ac it stops if i turn Ac on high vehicle temp rises higher than normal.. check the two 30 amp fuses and swap both relays any help this is stressing me out

phattyduck · Jul 31, 2019

191145 said:
Glad you found the fuse but like the others now I wonder what blew a 30 Amp fuse? With past front end damage the possibilities are many but I would try to find a short caused by a 'skinned' wire in contact with metal. I guess you'll know that you have a short if the fuse goes out again.

A blocked (stopped) electric motor draws significantly more power than a moving one. Maybe it was locked up in the accident, blew the fuse, and then wasn't replaced when the accident damage was fixed. I would also not be surprised if there are defective fuses out there too...

-Charlie

16vjohn · Aug 26, 2019

Very helpful thread, thank you to each contributor.

I wanted to add my own experience. No high speed, only low speed on the condenser fan. Followed all diagrams on troubleshooting procedures. After everything else checked out, I unplugged the primary fan plug to give it direct 12v, and the fan checks out. When I plugged it back in, everything started working normal.

Freaking loose connection at the fan connector plug. Added some dielectric grease two both connectors, now everything works normally.

Don't forget to check the easy things first like fuses and plugs.

m4gician · May 25, 2021

Hey guys I'm having the same symptoms here. Fans are only coming on LOW speed and it's affecting overall temperature if they can't come on high speed. I visually looked at the purple 30amp fuse and swapped it and the fans still run on LOW.

Based on this discussion is it likely to be one of the relays or fuses? The eye tests show the fuses look good but I don't have any spare fuses or relays to test with.

Radiator fan not coming on.

BenKenobi

John Clark

John Clark

John Clark

BenKenobi

John Clark

191145

Squiggtrust

phattyduck

16vjohn

m4gician

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