Richard, Clogzz,
It seems that the weird voltage on pin 3 of the rad switch that I noted in my original post is of some significance. If you check the circuit in the Haynes, you will see that pin 3 is connected to one end of the coil of relay 1500A. That is the relay which switches the motors into series mode. The other end of the coil should be connected via fuse F3(?) direct to the battery so, allowing for a slight voltage drop across the coil, the voltage should be the battery voltage at the rad sw. and at pin 2 of the relay.
Now that I know that with pins one and three (rad sw.) shorted without the ignition on this relay should activate, I listened for the click - heard nothing. With the relay pulled out, pin 1 of it's socket shows only 2.8 V.
Now the problem I have is finding fuse F3. This is supposed to be located in BB10, described as 'Supply box' which I assume is the engine bay box.
There is not even a position marked as such in the engine bay box and F3 in the 'passenger compartment' is OK - checked and double checked. (but that one should supply only the coils of the other relays anyway)
The two large 40A fuses supply the power for the motors and this appears at pin 3 of both 'motor' relays.
It looks like I will have to put it all back together and if I cannot find how to restore the full voltage to the coil of the relay, maybe rig a separate wire (with low amperage fuse) from a 12V source to pin 1 of the L/H 'motor' relay.
Your comments would be welcome.
Dave.
Advice needed Re: Xantia Cooling fans (non air con)
Moderator: RichardW
Thanks Anders for cheering me up 
Would that be the section which contains the big fuses - 80A, 60A etc. ?
I have six of these (including the two 40A fan motor ones) in a separate but ajacent section set in a row at 90* to the part that contains the smaller fuses. They all live under the same cover by the left inner wing
If the fault lies under there, thats where it will stay as I cannot see an easy way to get in there.
Thinking about it, the fuse required will only need to be a low aperage type as all it will have through it is the current for the relay coil.
Dave.
Would that be the section which contains the big fuses - 80A, 60A etc. ?
I have six of these (including the two 40A fan motor ones) in a separate but ajacent section set in a row at 90* to the part that contains the smaller fuses. They all live under the same cover by the left inner wing
If the fault lies under there, thats where it will stay as I cannot see an easy way to get in there.
Thinking about it, the fuse required will only need to be a low aperage type as all it will have through it is the current for the relay coil.
Dave.
Xantia Forte 1.8i, 16v X reg.(09/2000) 93K, aircon
Looking at the Haynes book now.
I wonder if the sender switch isn’t eating up the voltage.
As RichardW stated, and contrary to what I thought, the switch puts the pins to earth to operate the relays, and does not send voltage to them.
Try measuring the voltage on pin 3 of the sender plug, while unplugged.
If it’s still low, pull out relay 1500A, and check for 12 Volts on the live relay coil terminal in the relay socket.
If it lacks there, the fault is upstream, as per Anders.
Otherwise, put the relay back in, just enough to make the relay coil pins touch the socket, and measure at the other end of the relay coil.
If it’s 12 V without the sender, the fault is not in the downstream wire.
If it drops with the sender reconnected, and cold radiator, then the sender is cactus.
It would be better to measure with a lamp, because it gives an indication of current flow, while multimeters give readings even from strays and high leakages.
I’m playing here with a 12 Volt relay from an ordinary household microwave oven.
The resistance of the coil is 160 Ohms.
I wonder if the sender switch isn’t eating up the voltage.
As RichardW stated, and contrary to what I thought, the switch puts the pins to earth to operate the relays, and does not send voltage to them.
Try measuring the voltage on pin 3 of the sender plug, while unplugged.
If it’s still low, pull out relay 1500A, and check for 12 Volts on the live relay coil terminal in the relay socket.
If it lacks there, the fault is upstream, as per Anders.
Otherwise, put the relay back in, just enough to make the relay coil pins touch the socket, and measure at the other end of the relay coil.
If it’s 12 V without the sender, the fault is not in the downstream wire.
If it drops with the sender reconnected, and cold radiator, then the sender is cactus.
It would be better to measure with a lamp, because it gives an indication of current flow, while multimeters give readings even from strays and high leakages.
I’m playing here with a 12 Volt relay from an ordinary household microwave oven.
The resistance of the coil is 160 Ohms.
2002 C5 2.0i AL4 230,000 km 76372389
Clogzz,
As I said in my earlier post, there was only 2.8 volts on pin 3 of the rad socket (unplugged) and on pin 1 of the 1500A relay socket. I didn't actually check pin 2, but as I knew that the the relay activated when I put 12V across the coil, it's a reasonable assumption that the voltage there would be similar with the relay in.
The fault is in the supply side as I proved this morning by running a wire from the battery, via a 10A fuse, to pin 1 of the relay.
With this in place the fans behave as they should when the pins in the rad socket are shorted.
As soon as I have the coolant back in I will run up to temp to check they still work OK.
I still have no idea where the fuse is ( F3 left hand side of Haynes circuit, direct from the battery) but as Anders suggested it would seem likely that the wire to or from it has corroded or burnt out.
I will make a more permanent job of my 'hot wire' and check the operation of the fans from time to time to be safe.
Dave.
As I said in my earlier post, there was only 2.8 volts on pin 3 of the rad socket (unplugged) and on pin 1 of the 1500A relay socket. I didn't actually check pin 2, but as I knew that the the relay activated when I put 12V across the coil, it's a reasonable assumption that the voltage there would be similar with the relay in.
The fault is in the supply side as I proved this morning by running a wire from the battery, via a 10A fuse, to pin 1 of the relay.
With this in place the fans behave as they should when the pins in the rad socket are shorted.
As soon as I have the coolant back in I will run up to temp to check they still work OK.
I still have no idea where the fuse is ( F3 left hand side of Haynes circuit, direct from the battery) but as Anders suggested it would seem likely that the wire to or from it has corroded or burnt out.
I will make a more permanent job of my 'hot wire' and check the operation of the fans from time to time to be safe.
Dave.
Xantia Forte 1.8i, 16v X reg.(09/2000) 93K, aircon
Why don't you guys who are good with elecs, fit an overide switch to your fans? That way if any doubt exists you can just go to manual and know beyond any doubt that your engine cooling fans are working. 
James. (Nr M67 East of Manchester).
Dark Blue ZX 1.9D Auto 1994 'L' 5 dr (modified) Aura. 98K miles used daily. Ave mpg 40
Wedgewood Blue 75 CTD auto Connoissaur. 2002. 144k. used daily. ave mpg 40 ish.
Dark Blue ZX 1.9D Auto 1994 'L' 5 dr (modified) Aura. 98K miles used daily. Ave mpg 40
Wedgewood Blue 75 CTD auto Connoissaur. 2002. 144k. used daily. ave mpg 40 ish.
That’s definitely on the cards !
No fan problems for now, but when my turn comes, I’ll look into operating the fans by wiring them to the fog lights that I never use.
That will save me the trouble of pulling a new wire through the bulkhead, not an easy task, apparently.
And I will have to tell eventual other drivers of the modified car to turn on the fog lights when the temperature rises.
No fan problems for now, but when my turn comes, I’ll look into operating the fans by wiring them to the fog lights that I never use.
That will save me the trouble of pulling a new wire through the bulkhead, not an easy task, apparently.
And I will have to tell eventual other drivers of the modified car to turn on the fog lights when the temperature rises.
2002 C5 2.0i AL4 230,000 km 76372389
Clogzz,
I don't have a 5 and 5A - well I do actually but the sockets they are plugged into are unmarked - just big, chunky orange plastic stamped 40A on top. These are the ones that that pass the current for the motors.
The F3 that lives in the main box under the dash (10A) only supplies the coils of the changeover and L/H fan relays when the ignition is on.
I have the usual collection of small fuses (5, 10, 25A etc,) in the engine bay box but these are numbered in a weird random way : 7, 5, 11, 1, 4 etc. not nice and neat as in the main box. There is not even a numbered slot for 3.
I have to assume that one of these is the one that should supply the coil for the R/H fan relay but it's somewhat academic now for me.
The extra wire works OK and both fans cut in at around 90*.
Not a very elegant solution but if needs must .............
Thanks for your help on this one.
Dave.
I don't have a 5 and 5A - well I do actually but the sockets they are plugged into are unmarked - just big, chunky orange plastic stamped 40A on top. These are the ones that that pass the current for the motors.
The F3 that lives in the main box under the dash (10A) only supplies the coils of the changeover and L/H fan relays when the ignition is on.
I have the usual collection of small fuses (5, 10, 25A etc,) in the engine bay box but these are numbered in a weird random way : 7, 5, 11, 1, 4 etc. not nice and neat as in the main box. There is not even a numbered slot for 3.
I have to assume that one of these is the one that should supply the coil for the R/H fan relay but it's somewhat academic now for me.
The extra wire works OK and both fans cut in at around 90*.
Not a very elegant solution but if needs must .............
Thanks for your help on this one.
Dave.
Xantia Forte 1.8i, 16v X reg.(09/2000) 93K, aircon