Cooling fan issues

All aspects of tuning,modification and repairs to the BX 16valve.
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K168BAN
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Cooling fan issues

Post by K168BAN »

Hi Folks, seeking a bit of technical advice here, basically seems my cooling fan's have decided to go on strike during car's lack of use over past 6 weeks!! They both work fine if wired up direct to battery, so have come to the conclusion its down to the switch on side of rad that's at fault??? Would appreciate any advice as to any other possibilities...if there are any?? - Thanks.
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Adrian E
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Post by Adrian E »

Hiya

If you pull the plug off the sensor on the rad and use a short piece of wire to short across from the earth lead to each of the +ve terminals for low and high speed and it works correctly on both settings, then it does sound like the fan switch has failed.

I'd be surprised if it's failed on both speeds at the same time - usually one goes first before the other. Having said that, it never used to run on full speed unless mid-summer after a good hard run.

The fan switch you want is for a diesel - part number should be on an invoice from Andyspares in the file :)

If the fans don't cut in at both speeds when shorted, it suggests the device that controls the low speed running has failed.
K168BAN
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Post by K168BAN »

Cheers Adrian, Have actually ordered the rad fan sensor from GSF today & am collecting it in the morning. Was told i may need some other switch that goes into block, but to try the rad sensor first?? Was running fine till i parked car up 6 weeks ago, then found fans were not cutting in when i started her up at weekend :? Switched engine off before she overheated thou. :D
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Adrian E
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Post by Adrian E »

There will be an ECU temperature feed in the water manifold (blue connector) but that won't make a difference to fans running. not sure what else they could be talking about?

The other thing I mentioned is the ballast that controls the half speed running - if the fans work on full speed only using the test I described then the ballast may be faulty - it's around the rad somewhere but I've never needed to find it!
K168BAN
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Post by K168BAN »

Tried the test you mentioned Adrian, & the fans worked at both speeds when contacts were bridged with wire, but now ive fitted the new rad thermo sensor nothing happens until 90 degrees, then they both cut in :? Obviously something wrong somewhere, but does it really matter if the low speed fan's not working as surely engine aint going to get a chance to overheat with them both cutting in as they are anyway??
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Post by K168BAN »

Surely there must be other valver's with low speed fan not working & perhaps owners won't even be aware??
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Adrian E
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Post by Adrian E »

Hiya

Nothing ever does happen till they hit 90 degrees - the guage is a VERY silly design with where the temp is marked. With the low temp diesel fan switch they should pretty much run on low speed when stationary after a good blast. I never had them kicking in at full speed unless it was VERY hot out and I'd got the temps right up on a run.

Both fans always cut in together - they only come with 1 fan, the other has been added and the wiring spliced by the garage that fitted it. They should both run at either low or high speed at the same time
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Post by K168BAN »

Cheers for that...was obviously confused about the high/low speed, as i assumed low speed would be = 1 fan & high speed = 2...wasn't aware you'd modified the set-up. - So therefore ive nothing to be concerned about now really. - Not sure if new thermo switch is like for like, as i ordered it from GSF by the regd. so probably won't be a diesel one, but just glad to have fans working again for so little cash & effort :D Thanks for your help & advice Adrian...much appreciated.
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Adrian E
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Post by Adrian E »

No probs - the diesel switch just gives a bit of extra reassurance by making the fans run on low speed at a lower temperature. In summer they could just about be heard running most of the time if in stop-start traffic.

The single fan with 2 speeds is standard, unless the car had air-con which is why the 2nd hole for another fan is already built in on the car. Adding a 2nd fan was a belt and braces way of keeping them running sweet, although our phase 1 16V hasn't had it done as it never seems to run hot at all.
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