Radiator Fan - 2 speed

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trundletruc
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Radiator Fan - 2 speed

Post by trundletruc »

My 1984 van has a 2 speed radiator fan and must have been one of the earliest with this feature. I have had the van a long time and have never had any problems with overheating and have hear it working occasionally. However, whenever I test it by joining the contacts in the fan's connector on the switch, the slow speed works fine but when I move to the contacts for the fast speed it blows the fuse.
Initially, it had an 8 amp fuse, as per the owner's manual (have I got an out of date manual which refers to a one speed fan, I wonder?). I therefore looked at the wiring diagrams for all the years and noticed the power wires are all 2.5mm and increased the fuse to 16amps. Now I am wondering if I can put a 25amp fuse in as the later diagrams show a 30 amp fuse?
Or will the fan work satisfactorily with the 16amp fuse as I notice the temperatures for the two speeds overlap and the fan will not have the initial shock load of starting the fan when it cuts in on the fast speed? I could mimic this by having a pair of contacts wired together on the test wire, starting the slow speed and then while it is running connect the other terminal to the fast speed. Before I do this can anyone see a problem and have other people had the same problem?
I am just a bit worried that if does get hot enough to need the fast speed it will cut out completely!
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adie89
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Re: Radiator Fan - 2 speed

Post by adie89 »

The fuse is blowing because it’s currently the weakest point. Uprating the fuse will move that weak point perhaps to cables or fuse board. If it worked originally but not now, then something has failed. So fault find before you uprate.

Check all connections are clean and tight, any dirt or corrosion will increase resistance and force the motor to try and draw more current.
If you have a multi meter, disconnect the wires and tes the resistance. 6 ohms or less is acceptable, any more and it points to dirty or loose connections, failed wires. It only takes a few of the copper strands to break to increase the strain on the rest of the wire. You don’t want to melt your fuse board!
The motor could also be slowly seizing up by loosing lubricant or the bearings failing, they are after all probably original to the van. Motor then tries to work too hard, draws too much current, blows fuse. Add in old wiring and it’s easy to exacerbate a small problem. Check the fan, disconnect the power because it auto runs and will hurt a lot. if it’s stiff to turn or has play in the fan shaft, it is failing.
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937carrera
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Re: Radiator Fan - 2 speed

Post by 937carrera »

There's a wiring diagram for an 83-84 vanagon on the Samba https://www.thesamba.com/vw/archives/info/wiringt2.php

According to that fuse 7 should be a 16 amp fuse. Current track 87

Are you on ceramic / bullet fuses or the later blade type ?

All good & valid maintenance advice from adie89 BTW
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jrt
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Re: Radiator Fan - 2 speed

Post by jrt »

I've got a two speed fan (83) with the bullet fuses and it also has a 16 amp fuse in it as mentioned. This rating is also stated in the vans manual. Give all the fuse board contacts a good clean as they easily become tarnished/dirty. Image
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jrt
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Re: Radiator Fan - 2 speed

Post by jrt »

....funnily enough when we first got our van it blew the fan fuse on our first big trip out and thinking i had a one speed fan i did the usual checks to find out it was two speed and it had an eight amp fuse in it. The post was on here but it looks like it's long been deleted.
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trundletruc
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Re: Radiator Fan - 2 speed

Post by trundletruc »

Thanks for your help. My van has the early fuse board as in JRT's diagram and I have already put in a 16amp fuse as on the wiring diagrams. (Fuse 7)
My van probably came with an outdated owner's manual!
The first stage (slow speed) appears, on the wiring diagrams, to work without any relay but the 2nd stage (fast) does have one. Can anyone tell me where in the van this relay is because it is not on the fuse board?
I will check all the contacts and the relay when I find out where it is.
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937carrera
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Re: Radiator Fan - 2 speed

Post by 937carrera »

jrt wrote: The post was on here but it looks like it's long been deleted.

Still here, but in the archive :wink: :)

http://archive.club8090.co.uk/viewtopic ... 39&t=94553
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jrt
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Re: Radiator Fan - 2 speed

Post by jrt »

937carrera wrote:
jrt wrote: The post was on here but it looks like it's long been deleted.

Still here, but in the archive :wink: :)

http://archive.club8090.co.uk/viewtopic ... 39&t=94553
Ah, thanks for that...brings back a few memories. Don't think i used the spare fan as it's now in the shed...2011 eh?, still not replaced the vans heater blower :oops: :lol:
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937carrera
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Re: Radiator Fan - 2 speed

Post by 937carrera »

We don't seem to have a decent photo of where the relay is, but this thread should help - look above the earth crowns you just cleaned.

http://forum.club8090.co.uk/viewtopic.p ... &p=8056599

When you have found it, how about uploading a photo to help others who will have this problem :)
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Oldiebut goodie
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Re: Radiator Fan - 2 speed

Post by Oldiebut goodie »

Image
Don't know if the pic will stay up as pbucket have changed/are changing again.

Blooming heck - I have been posting that pic for the last 5 years!
(That is a 50A fuse for that relay)
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Re: Radiator Fan - 2 speed

Post by CovKid »

I found unseating and reseating relay stops the fuse blowing any more
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trundletruc
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Re: Radiator Fan - 2 speed

Post by trundletruc »

Thank you all for your help over this. I cleaned all the contacts and took out the relay and tested it. Put it back together and it all works using the 16amp fuse! So it would seem that VW boobed by putting the wrong owner's manual in the van when they sold it. So the conclusion is that if you have a 2 speed Radiator fan 8amps is definitely wrong. When testing I did swop over from low to high contacts quickly before the fan stopped turning!
Preparing for the future I have a spare radiator fan from a 1989 Caravelle. This has the same part number (251 959 455) as the fan in my 84 van but with the suffix F on the end. I assume that this is a higher wattage fan than the one presently in the van. I have looked in various spare parts sites on the web but cannot find this particular one mentioned. 200/300 watts has suffix G, 450 watt has M and 500 watt has N. Any ideas what my spare one with an F is?
If I have to fit this fan, at some time, I can see no reason for not using a 25amp fuse (bullet type). The wiring sizes on all the diagrams from 1984 to 1987 have the same size. The present 16amp fuse is certainly not going to be big enough for the extra power, it is only just coping with the present fan. The fans sold now are all probably the later type with the higher wattage.
Brickwerks sell a resistor? Is this only for vans which have air conditioning or turbo diesel? My wiring diagrams show a resistor for the low speed being in the motor itself.
It is never easy sorting out what's what when there are so many changes. So thanks for all you help.

Incidentally, if you have to get a new starter motor, and now it is one fits all, the main wire to the back is different for the later years. Be careful you don't overload your earlier wires.
Trundletruc 1984 DG-DJ Devon Moonraker

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