Discussion
Im having trouble with the fans on my 4.3.
Initially it started with a strange buzzing noise from the footwell which turned out to be the relay serving the fans. It overheated, melted its casing and subsequently I found the fans were not coming in - that was on the London tunnel run. I replaced the relay with the horn relay, which is identical,and bypassed the otter switch and all works albeit with the fans permenantly on. I have now replaced the otter switch and all appeared ok for about 5 mins of normal temperature running. The buzzing noise appeared from the footwell again and the fans stopped. Strangely the noise changed pitch when the car was revved.
I have brought some bosch relays and am goin to try them together with another otter switch.
The electrical diagram in the Heath book illustrates blocks into which wiring dissapears but doesnt show the arrangement within the blocks. Does anybody have any information regarding these blocks or any advise that they could give me.
In anticipation.
Graham.
Initially it started with a strange buzzing noise from the footwell which turned out to be the relay serving the fans. It overheated, melted its casing and subsequently I found the fans were not coming in - that was on the London tunnel run. I replaced the relay with the horn relay, which is identical,and bypassed the otter switch and all works albeit with the fans permenantly on. I have now replaced the otter switch and all appeared ok for about 5 mins of normal temperature running. The buzzing noise appeared from the footwell again and the fans stopped. Strangely the noise changed pitch when the car was revved.
I have brought some bosch relays and am goin to try them together with another otter switch.
The electrical diagram in the Heath book illustrates blocks into which wiring dissapears but doesnt show the arrangement within the blocks. Does anybody have any information regarding these blocks or any advise that they could give me.
In anticipation.
Graham.
tom's dad said:
Im having trouble with the fans on my 4.3.
Initially it started with a strange buzzing noise from the footwell which turned out to be the relay serving the fans. It overheated, melted its casing and subsequently I found the fans were not coming in - that was on the London tunnel run. I replaced the relay with the horn relay, which is identical,and bypassed the otter switch and all works albeit with the fans permenantly on. I have now replaced the otter switch and all appeared ok for about 5 mins of normal temperature running. The buzzing noise appeared from the footwell again and the fans stopped. Strangely the noise changed pitch when the car was revved.
I have brought some bosch relays and am goin to try them together with another otter switch.
The electrical diagram in the Heath book illustrates blocks into which wiring dissapears but doesnt show the arrangement within the blocks. Does anybody have any information regarding these blocks or any advise that they could give me.
In anticipation.
Graham.
My 4.3 was been re-wired to supply the fans direct from the alternator. I have upgraded this to one relay and one fuse for each fan, direct from the alternator. The relays and fuses are mounted by the windscreen washer bottle to keep wire length to a minimum. The relays are switched from the otter. IIRC the original wiring is for one fan on the 4.3. Once twin fans are added they draw a lot of current for the one wire and one relay.
The buzzing noise sounds like either the fans are now starting to draw too much current,or the connection for the relay is a poor/loose one.It would be good if you could use an ammeter to see how much current the fans are drawing.
Either way it is a far better idea to have each fan running on its own circuit,with its own relay and fuse.On my first chim i had the unplesant experience of the fuseboard catching fire,which turned the battery into a large candle,then burnt the heater box above it out!This all started with a melted relay on the fan circuit.I was then told by my dealer that its not unknown!All this would have been prevented by separating the fan circuits.You can separate the fans quite easily,using the power from the starter supply,or,if you want to be really neat and do a proper job,then you can trace the pins out from the back of each connector at the fuseboard(find the switched otter live and the fan supply),and put your relay and fuse in the footwell.Not wanting a repeat of what happened to my chim,this is what i did on my first griff,the later cars have two circuits as standard.
Either way it is a far better idea to have each fan running on its own circuit,with its own relay and fuse.On my first chim i had the unplesant experience of the fuseboard catching fire,which turned the battery into a large candle,then burnt the heater box above it out!This all started with a melted relay on the fan circuit.I was then told by my dealer that its not unknown!All this would have been prevented by separating the fan circuits.You can separate the fans quite easily,using the power from the starter supply,or,if you want to be really neat and do a proper job,then you can trace the pins out from the back of each connector at the fuseboard(find the switched otter live and the fan supply),and put your relay and fuse in the footwell.Not wanting a repeat of what happened to my chim,this is what i did on my first griff,the later cars have two circuits as standard.
Mine has done exactly the same, looks like a re-wire is in order, I was thinking of doing this anyway. Mine did this on the way down to Le-Mans this year, stuck a bit of plastic in the relay to keep the contact and all was well, you just have to remove the relay when you stop.
How do you re-wire from the alternator, any chance you could discribe it for us?
>> Edited by dougal on Tuesday 29th November 15:01
How do you re-wire from the alternator, any chance you could discribe it for us?
>> Edited by dougal on Tuesday 29th November 15:01
Funny, I seem to have the same problem. Fans just don't work, no other symptoms. I have replaced the otter switch and the relay and checked the fuse. When I bypass the otter switch, I can hear the relay clicking but the fans don't work. I have checked the current to the fans with the switch bypassed, and there seems to be nothing there. Like you I have two fans but only one relay/fuse.
Thanks for your contribution tomtomnot.
I am going to explore this further tomorrow-got the day off work. Like the idea of exploring the double relays suggested. Like Dougal, I would also like the finer points explained in more detail, Im a bit thick when it comes to electricals.
Appreciate your suggestions.
dougal said:
How do you re-wire from the alternator, any chance you could discribe it for us?
>> Edited by dougal on Tuesday 29th November 15:01
I don't have the car to hand - or any pictures - but I'll do my best!
As long as you understand how a relay works, and how to connect one, it's easy. I strongly suggest you disconnect the battery to avoid short-circuit disasters.
On the back of the alternator there's a screw terminal which is live. Use this to supply the relay switched positive* by connecting to it with a suitable ring terminal. Use a wire size correct for the application - I forget what the current rating of the fans is, but I guess 25 amp or 30 amp wire should do, assuming the fans draw about 10 amps each. Either use a 'spur' of wire to split the supply to each relay, or even run two wires from the alternator. Fuse each supply before the relays. It should preferably be done as close to the alternator as possible but after my first fuse holder melted I ended up putting the fuses just before the relays which are located by the washer bottle.
The Relay switched earth* should be connected to the fan positive (one relay for each fan) leaving the old fan supply disconnected. Leave the existing fan earths connected though. So now when each relay switches on, the alternator feeds 12v through to each fan.
To make the relays switch via the otter is simply a case of finding which of the otter terminals is earthed and leaving that one connected. Disconnect the other otter terminal and connect the terminal (not the disconnected wire) instead to each relay control negative* again using a spur of wire to branch to each relay. Wire size is non-critical here, any multistrand automotive stuff will do.
The easiest way to connect each relay control positive* to 12v is to jump it over with a short length of wire from the other 12v terminal on that relay - the one connected via a fuse to the alternator.
Now when the otter switches 'on' at fans on temperature, the connection is made between alternator 12v and earth via each relay control circuit and the otter. In turn the relays are energised, and hey presto current can flow from the alternator to the fans. What's more it's a high a voltage as you can get, so the fans work as strongly as possible. Make sure the wiring's as tidy as possible. Keep it well away from exhaust manifold heat, using concertina conduit if necessary. I secured the relays to a metal bracket fixed to one of the washer bottle bolts. It's nice and cool there, but a bit exposed, so a plastic bag over the relays and fuses keeps them clean and dry.
Test the job by shorting both otter terminals together with a screwdriver or similar. Both fans should come on.
Don't blow anything up, proceed with caution, if in doubt consult an expert etc...
* (I can't remember which number connector on the relay it is - maybe someone with a better memory than me will post - I just use the diagram on the relay) just use the diagram on the relay)
>> Edited by griffter on Tuesday 29th November 22:16
interesting day, will fill in the detail later. A fault found.Gassing Station | Griffith | Top of Page | What's New | My Stuff