Rad fans permanently on- please help!

Hi All,

My rad fans are on permanently from the moment the battery is connected. Does anyone have any ideas?

My temp gauge has also packed up- are the two related?

Thanks

Jon

When this happened to me in the G33, the relay had melted internally welding itself to the on position. I would check that first, then the otter switch

Thanks!

Anyone know relay position?

My rad fans are on permanently from the moment the battery is connected.

Hi Jon,
The first thing I would do is go to the rad switch which is situated on the offside of the rad, and unplug it then see if the fan still runs with the ign on.

There is a relay for the fan which is energised by the rad switch but I have two different positions for it, one being 1990 model year and 1986 model year. The fuses for each are mounted above the fuse box. If fan still runs when the rad switch is disconnected, the best way to identify the relay is with the ign on, unplug each relay, one at a time replacing each relay before moving to the next one, until the fan stops..... at which point you will have located the fan relay.

Thanks John, will get checking!

My temp gauge has also packed up- are the two related?

No, they are not related..... go to the thermostat housing, and there should be a sensor on the off side of it..... to check, with ign on, remove the two spade connectors and short them together.... the gauge should read full scale. There are no relays in this cct, but the wires pass through a few connectors. But see what happens first when the wires are shorted.

My money would be on the rad sensor also .
AC cars have a twin relay and fuse holder in the bonnet area ..well the ones I've seen anyway .RHS near headlamps /air horn .
Often the fuse/holder is melted .

My rad sensor went phut a couple of years ago. My problem was the other way - didnt detect high temp, hence the temp gauge went higher and higher etc..

So I think they are prone to failure. Cost around £20 from memory.

.
Good point, I think you will need to uprate &/or seperate the relay circuit into two components, and then uprate the fan power switching relay current rating as you now have two high performance fans that likely pull more current than the OE relay was specified... if you simply replace with OE, you will more than likely be back in the same position in short order.

Martin

If you have two fans, its always best to have them on separate relays and fuses, the current draw on startup is very high, hence melted relays and fuse holders etc.

My GTA has twin fans and I will be looking at this. I am also considering wiring one of the unused switches as an override

Can anyone point me in the direction of the correct upgrade here? What spec am I looking for?

Thanks for all your help!

Jon

Does it not have twin relays already ? Up the rating ?

Does it not have twin relays already ? Up the rating ?

Of course that throws up more questions than answers.
If an Alp has two OE fitted rad fans, there will be two relays according to the manual/s. However, if after market high performance fans have been fitted as Martin F suggests, one would have to know the running current rating of each fan, having identified that, a decision would have to be made as to whether the OE relays could carry the extra current. If not, I know that Lucas make relays that will fit the Relay sockets of the Alp, and a trawl through their web site should come up with an alternative Relay. However.... Auto relays in general (OE type included) are designed to carry high currents in the range of 20 to 30 amps which should be capable of carrying the current for even uprated fans.
Now..... in Jon`s case, he states "Fans".... it would be very unlikely that the Relays are at fault, as the chances of both relays failing together is very remote. So at the moment, as Lee suggests, my money is on the Rad switch, I would be checking that before I went any further.
There is, of course, another angle to this.... If the Alp was only fitted with one fan from new, and somewhere along the line, someone decided to replace the OE fan with two after market fans and just wired the extra fan across the other, then the one relay would be asked to carry the current of two fans. That just might overload the one relays contacts which, if they weld themselves together, would cause the two fans to run.... just a thought

My GTA has twin fans and I will be looking at this. I am also considering wiring one of the unused switches as an override

I did this and it certainly helps. You can help the car to avoid becoming heat soaked when sat in traffic etc.

Does it not have twin relays already ? Up the rating ?

Of course that throws up more questions than answers.
If an Alp has two OE fitted rad fans, there will be two relays according to the manual/s. However, if after market high performance fans have been fitted as Martin F suggests, one would have to know the running current rating of each fan, having identified that, a decision would have to be made as to whether the OE relays could carry the extra current. If not, I know that Lucas make relays that will fit the Relay sockets of the Alp, and a trawl through their web site should come up with an alternative Relay. However.... Auto relays in general (OE type included) are designed to carry high currents in the range of 20 to 30 amps which should be capable of carrying the current for even uprated fans.
Now..... in Jon`s case, he states "Fans".... it would be very unlikely that the Relays are at fault, as the chances of both relays failing together is very remote. So at the moment, as Lee suggests, my money is on the Rad switch, I would be checking that before I went any further.
There is, of course, another angle to this.... If the Alp was only fitted with one fan from new, and somewhere along the line, someone decided to replace the OE fan with two after market fans and just wired the extra fan across the other, then the one relay would be asked to carry the current of two fans. That just might overload the one relays contacts which, if they weld themselves together, would cause the two fans to run.... just a thought

I know for a fact, that a standard automotive 30amp relay is not man enough for a pair of Sierra Cosworth fans as fitted to the G33. They melted 2 relays both rated 30 amps. Once each fan had its own 30amp relay all was well