Installing A New Radiator Thermoswitch

[humanz 3]

Ok, I've bought a new thermoswitch as I was a bit concerned about the temperatures the fan was cutting in at. I know I've got to drain the radiator, but once I've gotten the switch in, are there any precautions I should take when refilling the cooling system? Or anything in particular I should make sure I do? I also want to flush the radiator at the same time. Can someone give me an idea of how much coolant I should buy?

 

What about the wires to the thermoswitch itself? I know one will be a live feed from the battery, and the other two go to the resistor and the fan. Using a multimeter, how can I figure out which one is the live? Does the negative lead on the multimeter go to an earth point or somewhere in the circuit itself? (kinda new to multimeters). How will I know which connector on the thermoswitch is the one for the plug from the live feed?

 

Finally, I've got a twin fan setup, but one of my fans has died. I'm looking to replace it within a few weeks. Will I have to disconnect/drain the radiator in order to replace the dead fan in the twin fan housing?

 

If I've got to drain the system, I guess I should wait til I've gotten a working fan before I install the new thermoswitch.

Thanks.

[pug_ham 245 3 Cars]

Ok, I've bought a new thermoswitch as I was a bit concerned about the temperatures the fan was cutting in at. I know I've got to drain the radiator, but once I've gotten the switch in, are there any precautions I should take when refilling the cooling system? Or anything in particular I should make sure I do? I also want to flush the radiator at the same time. Can someone give me an idea of how much coolant I should buy?

 

What about the wires to the thermoswitch itself? I know one will be a live feed from the battery, and the other two go to the resistor and the fan. Using a multimeter, how can I figure out which one is the live? Does the negative lead on the multimeter go to an earth point or somewhere in the circuit itself? (kinda new to multimeters). How will I know which connector on the thermoswitch is the one for the plug from the live feed?

 

Finally, I've got a twin fan setup, but one of my fans has died. I'm looking to replace it within a few weeks. Will I have to disconnect/drain the radiator in order to replace the dead fan in the twin fan housing?

 

If I've got to drain the system, I guess I should wait til I've gotten a working fan before I install the new thermoswitch.

Thanks.

I usually buy a 5l tub of coolant but don't use it all, Most I'll use from it is 3l.

 

Full system capacity is 6.6l but unless you have drained the heater matrix as wel, you'll be lucky to get 5.5l total in imo.

 

When filling the system you have two bleed points to open before you start. One is on a hearter mastrix hose near the bulkhead & the other is on the small pipe that comes out of the thermostat housing above the cap.

 

Wires for the thermoswitch, if you have three individual wires you have the older style of switch, two vertical & one horisiontal. Later switchs have a blue three pin plug so you can't get the wrong. I think it should have a permanent 12v through the live feed with the battery connected, it doesn't have a permanent earth afaik just switches power to the fan motor.

 

On yours, I think the positive will got to the single horisontal pin & the high or low speed to the two parrellel vertical ones.

 

You will be best to do the fan at the same time as everything else, it is just about possible to swap the fan without removing the rad again but its not easy & best done with the rad out to avoid damaging it with a fan blade imo.

 

Graham.

[humanz 3]

When filling the system you have two bleed points to open before you start. One is on a hearter mastrix hose near the bulkhead & the other is on the small pipe that comes out of the thermostat housing above the cap.

 

Thanks Graham. Will wait until I get a replacement fan sorted then. How do you open the bleed point? As in simply disconnect it so coolant flows out? My heater matrix has been bypassed, so does this mean I don't have to worry about opening that bleed point?

 

Cheers.

[DrSarty 90 1 Cars]

Bleed points are at high spots in the cooling pipework. You've mentioned that you've disconnected your heater matrix; there's usually one there on the top hose just before it goes through the bulkhead. It's a plastic, knurled screw/vent that you loosen to let trapped air escape.

 

There's often another right by the thermostat housing, if not actually fitted to it; same thing, a plastic screw big enough to turn by hand, although it does have a flat head screw slot in the centre.

 

Bleeding is best done in this fashion, as those bleed screws are there for a reason. I've often had no problem with trapped air ( ), by running up the engine with the expansion bottle cap off, and (wearing gloves) squeezing the larger coolant hoses to force air through the system to escape out of the bottle.

 

Just a note on the thermoswitch in the rad: you (and Graham) are right, in that one PERMANENT live feed goes in to one pin, either direct from the battery pos terminal or from the shunt (power distribution) box on the slam panel or battery tray. The other 2 pins merely direct that power to either of the other 2 pins depending on the water temp affecting something inside the thermoswitch; I picture it as a wiper. Pin 2 should be used to take that 12v live down - via the resistor - to the positive input of the fan, and pin 3 goes directly, no resistor in series to the same positive feed of the fan. Yes: the fan has 2 pos wires coming in and one earth. The latter is just a short, thick wire, going to a good earth on the chassis/body.

 

Some people remove the resistor. I like many others get on fine with it, and then fan goes from quiet, slow speed (through the resistor) up to full speed as necessary.

 

By following what Graham has suggested, or just looking at the wiring and plugs you've removed, you should be able to figure out which pin on the thermoswitch originally went to what.

 

Good luck & I HTH.

[pug_ham 245 3 Cars]

The bleed point is in the hose so just because the heater matrix is removed / bypassed the bleed point shoud still be in the hose behind the engine imo & its best if its open when you refill the system.

 

Graham.

[Super Josh 4]

As you have the twin fan set up, it is wired differently to the single fan set up.

 

There is no resistor for the low fan speed. The 2 fans are either run is series for low speed or in parallel for high speed. This is all controlled by the 3 relays in the black box by the slam panel.

 

So with this set up, you say that one of your fans has died? If it doesn't work at all, then you will probably have no fans in the low speed and just one fan working in the high speed position.

 

Also be aware that the postive supply to the thermoswitch is controlled by the ignition in AC equipped, twin fan set up cars. So you WON'T find a permannent live with your multimeter when probing the thermoswitch

 

Hope that helps,

 

 

Josh

[DrSarty 90 1 Cars]

To borrow a line from Jack Nicholson: "don't a feel like the f*ckin' asshole"

 

Edited March 25, 2009 by DrSarty

[GTI6BOY 29]

You dont need to drain the system just quickly have the new 1 ready to screw in and you wont loose any water

[taylorspug 7]

You dont need to drain the system just quickly have the new 1 ready to screw in and you wont loose any water

 

And leave the rad cap on so it doesnt drain as quick.

[humanz 3]

As you have the twin fan set up, it is wired differently to the single fan set up.

 

There is no resistor for the low fan speed. The 2 fans are either run is series for low speed or in parallel for high speed. This is all controlled by the 3 relays in the black box by the slam panel.

 

So with this set up, you say that one of your fans has died? If it doesn't work at all, then you will probably have no fans in the low speed and just one fan working in the high speed position.

 

Also be aware that the postive supply to the thermoswitch is controlled by the ignition in AC equipped, twin fan set up cars. So you WON'T find a permannent live with your multimeter when probing the thermoswitch

 

Hope that helps,

Josh

 

Only one prob Josh. I do have a twin fan shroud and two fans, but I believe the loom that's in the car now (removed from another car) came with a fan resistor wired in. The second fan was discovered to be not working while the electrician was repairing damage to the loom. As I'm not sure if the electrician has used the relays in the black box for the fan, I think I'll leave the job of wiring up the second fan to him instead of trying to figure out if he made any changes to the wiring. If I can find a permanent live, I will install the thermoswitch myself.

 

Thanks all.

[GTI6BOY 29]

Why do you want 2 fans?

 

We run 400bhp with 1 fan with no problems?

[jimistdt 1]

Why do you want 2 fans?

 

We run 400bhp with 1 fan with no problems?

 

 

'Tis a lil warmer in Barbados!

Edited March 26, 2009 by jimistdt

[GTI6BOY 29]

Lol...did not see that.

 

Maybe a fair point

[humanz 3]

Yeah. The car gets up to normal temperature failry quickly. It isn't a big deal once the car is moving. But when I'm stuck in traffic, the temp gets pretty close to the last white mark before the white area and I start to fret. Plus, I get alot of the heat coming into the passenger compartment once that happens. Rather uncomfortable.

[humanz 3]

Well, I had a go at installing the thermoswitch. Actually went smoother than I had imagined. Didn't lose much coolant (it did pour out tho, rather than a trickle) but I was ready with the new switch so...I just topped up the expansion bottle afterwards. Should I have bled the system??

[GTI6BOY 29]

no it will be fine

[Masekwm 2]

Seems like a good topic to bump:-

 

I fitted a new radiator today. and it's leaking from the side with the thermoswitch, should there be an O-ring or gasket on the thermoswitch?

[pug_ham 245 3 Cars]

should there be an O-ring or gasket on the thermoswitch?

IIRC there shoud be a copper washer undeneath the thermoswitch but I always put some ptfe tape on the switch threads as well.

 

The copper washer can be re-used & as yet I've never had one leak.

 

Graham.

[Masekwm 2]

Thanks Graham

 

The old radiator was leaking from the same side, from condition I thought it was the radiator, but on removing the thermoswitch something blew off in the wind.

 

I take it that was the remains of the copper washer I shall buy another, instead of paying OTT for another Peugeot "seal".

Edited November 30, 2009 by Masekwm

[pug_ham 245 3 Cars]

on removing the thermoswitch something blew off in the wind.

I'd be surprised if that was the washer, its quite a big copper one & on mine needed to be unscrewed from the thermoswitch to anneal it for reuse but just some ptfe tape shoud be good enough imo.

 

Graham.