Discussion
Step one: With the ignition switched off, bridge the 2 no terminals on the otter switch, should be in the radiator on a 450, [if not then on the swirl tank]. Turn on the ignition, if the fans dont run, turn off and check down at the bottom off the radiator [engine side] for the 2 no fan connectors, These can corode/ get wet/ dirty. Split them and clean thoroughly and copper grease them before you reconnect them. With the bridge still on the otter switch, turn on the ignition and the fans should run ok.
Remove the bridge let the engine run up to temp and check the fans kick in as they should at or about 90/92 degrees, good luck any further help/advice just ask, Tom.
Remove the bridge let the engine run up to temp and check the fans kick in as they should at or about 90/92 degrees, good luck any further help/advice just ask, Tom.
TJC46 said:
Step one: With the ignition switched off, bridge the 2 no terminals on the otter switch, should be in the radiator on a 450, [if not then on the swirl tank]. Turn on the ignition, if the fans dont run, turn off and check down at the bottom off the radiator [engine side] for the 2 no fan connectors, These can corode/ get wet/ dirty. Split them and clean thoroughly and copper grease them before you reconnect them. With the bridge still on the otter switch, turn on the ignition and the fans should run ok.
Remove the bridge let the engine run up to temp and check the fans kick in as they should at or about 90/92 degrees, good luck any further help/advice just ask, Tom.
Thanks, tried but didnt work, have wired a seperate switch, who's TomRemove the bridge let the engine run up to temp and check the fans kick in as they should at or about 90/92 degrees, good luck any further help/advice just ask, Tom.
jdwcd said:
Thanks, tried but didnt work, have wired a seperate switch,
Rad fans run like everything else does, with power and an earth. Their thermo-switches (aka otter switches) provide the earth (often via a relay) when the temperature reaches a pre-determined level. The fan has constant power. Finding the cause of an electrical problem is always by process of elimination.
If the switch was the problem, bypassing it by touching its two wires would have started the fan. So if that didn't work, you can assume the fan switch is good for the moment. You should go on. Do you have a multimeter? That makes these things easy. If not, do you have a length of spare wire?
+8
Try the horn, that is the fused circuit for the otter switch relay control circuit, the fan fuse is the relay power circuit.
Yep our Canadian friend was talking rubbish, all the cars have positive switched fans fired up from the relay(s) in the fusebox direct to the fans with the otter switch activing the relay by being grounded, whichever of the several layouts / fans / single or dual relay combinations was fitted to your particular model. The fans are fixed grounds to the front of the chassis under the rad.
Typically one of the fuses goes or the fan connector gets corroded, for both fans to fail its likely one of the fuses (horn or fan) or the relay itself (even where twin relays are fitted they were frequently daisychained so if the first fails the second one will never get switched.. one of those YMMV things in diagnosis)
Yep our Canadian friend was talking rubbish, all the cars have positive switched fans fired up from the relay(s) in the fusebox direct to the fans with the otter switch activing the relay by being grounded, whichever of the several layouts / fans / single or dual relay combinations was fitted to your particular model. The fans are fixed grounds to the front of the chassis under the rad.
Typically one of the fuses goes or the fan connector gets corroded, for both fans to fail its likely one of the fuses (horn or fan) or the relay itself (even where twin relays are fitted they were frequently daisychained so if the first fails the second one will never get switched.. one of those YMMV things in diagnosis)
"otter switch activing the relay by being grounded"
This part confuses me, my fusebox is out at the minute, but to get the fan relay to activate I have to apply a +ve to the input to the fusebox, not a -ve. I can't remember the block/pin number on the fusebox and I'm,at home now.
Scott
This part confuses me, my fusebox is out at the minute, but to get the fan relay to activate I have to apply a +ve to the input to the fusebox, not a -ve. I can't remember the block/pin number on the fusebox and I'm,at home now.
Scott
s6otty said:
"otter switch activing the relay by being grounded"
This part confuses me, my fusebox is out at the minute, but to get the fan relay to activate I have to apply a +ve to the input to the fusebox, not a -ve. I can't remember the block/pin number on the fusebox and I'm,at home now.
Scott
Ign switch feeds +12v to the coil in the relay, the other side is connected to the otter switch (GK) as the otter switch closes that circuit is completed to ground and the relay trips. ie the relay is switched by grounding not feeding. This part confuses me, my fusebox is out at the minute, but to get the fan relay to activate I have to apply a +ve to the input to the fusebox, not a -ve. I can't remember the block/pin number on the fusebox and I'm,at home now.
Scott
The power side feeding the relay normally comes directly from one of the buses in the fusebox and is permanantly live, although some have it off the main ign relay (70A) bus, and the fuse can be before or after the relay in the circuit ~ all depending on the location of the relay & infrequently how it was wired (some locations are hard wired and some cabled behind the fusebox). If you study my documentation of the internals of the fusebox hard enough it may all become clear
spend said:
Try the horn, that is the fused circuit for the otter switch relay control circuit, the fan fuse is the relay power circuit.
Yep our Canadian friend was talking rubbish, all the cars have positive switched fans fired up from the relay(s) in the fusebox direct to the fans with the otter switch activing the relay by being grounded, whichever of the several layouts / fans / single or dual relay combinations was fitted to your particular model. The fans are fixed grounds to the front of the chassis under the rad.
Typically one of the fuses goes or the fan connector gets corroded, for both fans to fail its likely one of the fuses (horn or fan) or the relay itself (even where twin relays are fitted they were frequently daisychained so if the first fails the second one will never get switched.. one of those YMMV things in diagnosis)
"Yep our Canadian friend was talking rubbish" Come on, we don`t want to fall out with our colonial friends! we all know how sensitive there all are Yep our Canadian friend was talking rubbish, all the cars have positive switched fans fired up from the relay(s) in the fusebox direct to the fans with the otter switch activing the relay by being grounded, whichever of the several layouts / fans / single or dual relay combinations was fitted to your particular model. The fans are fixed grounds to the front of the chassis under the rad.
Typically one of the fuses goes or the fan connector gets corroded, for both fans to fail its likely one of the fuses (horn or fan) or the relay itself (even where twin relays are fitted they were frequently daisychained so if the first fails the second one will never get switched.. one of those YMMV things in diagnosis)
Spend just noticed you live in Derbyshire ,seeing you are the electrical guru can you sort out my interior courtesy light and off side electric wing mirror? whats your hourly rate because i have now been trying to fix these two gremlins for two years
Also want to run a new fresh larger cable to my new fuel pump !where the hell does that come from and i`ve never done any of that soldering and cable heat shrinking.
Edited by SILICONEKID340HP on Thursday 29th December 21:33
The ignition relay (when switched on) should apply +12v at G-75, and then grounding G-71 (otter switch) makes the circuit across the relay coil. Some of the relay sockets you can reverse, but that one is hard wired IIRC.
It's only supposed to work when the ignition is high, if you test the way it sounds like you are doing you are probably finding a back ground through some other path (like making the indicators flash when the fans come on if you have a bad earth under the rad).
It's only supposed to work when the ignition is high, if you test the way it sounds like you are doing you are probably finding a back ground through some other path (like making the indicators flash when the fans come on if you have a bad earth under the rad).
Gassing Station | Chimaera | Top of Page | What's New | My Stuff