Mk3 Cavalier Owners Club | Vauxhall Cavalier Dot Com

Can anyone tell me where the thermo switch is located that controls the cooling fan for the alternator on the Cavalier V6? This is the small fan that is mounted on the transmission side of the engine with ducting from the front grill and ducting down to the alternator at the back of the engine. My fan is behaving erratically - cutting in and out at odd times, even when the engine is off.

There is no special thermo switch for the generator fan. There is only a special thermo switch at the radiator with brown and brown-yellow wires which triggers the second cooling stage including the generator fan.

Indeed, looking at the wiring diagram, it looks like a whole array of relays, with permanent live feeds from fuse 8 (under the dash) and fuse 34 (engine bay fuse box).

As Tobias suggests there is a thermo switch in the radiator.
Feed is from a relay k26 pin 6 (85 terminal) via a brown / yellow wire to the thermo-switch. (s29)

The other wire is brown from thermo-switch to earth / chassis.

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The alternator cooling fan motor (m23) has two main wires.

Relay controlled live from the permanent live rail. This is a red / black wire from relay k26 terminal B / pin 5 via the barrel shaped connector close to the battery (connector x5 pin 7).

The other wire from the alternator blower motor is a brown wire to ground / chassis via x5 connector pin 5

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So possible causes are: -
a faulty thermo-switch on the radiator,
Or
A faulty control relay
Or
faulty / dirty / corroded wiring or connection to the relay, thermo-switch or the alternator blower motor.

Thank you for these replies. I have indeed replaced the radiator thermo switch when I thought the fan noise was the radiator fan (and I guess it may well have been, in addition to the alternator fan). The radiator fan is now behaving normally but the alternator fan comes on when the radiator is only initially warm and stays on (occasionally cutting out and then restarting for a few minutes several times) when I turn off the engine. So it looks as though it might be a faulty control relay, particularly because of the intermittent nature of the fan operation. I'll try replacing the relay - if I can get one!

Although things have long since moved to multi-function electronic controlled fuse boxes, I am sure that there will be an equivalent relay available from somewhere.

Simply look at the existing relay, and look either for the pin layout, or for a GM part number.
From there, google is your friend.

Looking at this site.

http://www.catcar.info/opel/?lang=en&l= ... 0zNA%3D%3D

There are several part numbers, all showing as still available.
So you should be lucky.
I expect the relay to be in the engine bay fuse box.

As a long term follow up to this, I located the relay controlling the alternator cooling fan, located in the engine compartment fusebox - GM 90459640 (orange).
I replaced it in 2019 with a used orange relay sourced from eBay (at about £8.00) and all was well. However, the fan has just started playing up again, with it staying on sometimes for up to 2 hrs after turning off the engine. This was contributing to the car's battery occasionally going flat on me.
So I've now bitten the bullet and paid £35.00 for a new relay - seems an extortionate amount but, if it stays reliable for longer and saves degrading the battery, I guess it'll be worth it.

I suspect that it is the old addage...
Buy cheap, buy twice.

When it comes to electrics, although prices can seem extortionate, the 'proper' parts are usually able to last much longer.

But... since 2020, I have seen a lot of out-sourcing to Chinese suppliers and a significant reduction in reliability.
Read the small print on your packaging.

Parts made in Russia (spark plugs) or China (almost any copy part) should be considered as less than adequate quality. - based on feedback from various forums.

I've now replaced the orange relay supplying the alternator cooling fan with the rather expensive, but new, replacement. All is working well again, but I noted that the fuse supplying the relay located next to it in the fusebox - and hence the supply to the alternator fan - is rated 40amp. This seems rather a large current draw for what is a relatively small fan, but the erratic on behaviour of the fan, caused by the faulty relay even when the engine is off, may explain why my battery has been running down recently.

I suspect a fan running will indeed suck a lot of juice out of the battery.

Hope that is the fan issue sorted.

Being a Cavalier - on to the next 'unexpected' issue.

Robsey wrote: ↑Sat Nov 04, 2023 6:44 pm
But... since 2020, I have seen a lot of out-sourcing to Chinese suppliers and a significant reduction in reliability.
Read the small print on your packaging.

Parts made in Russia (spark plugs) or China (almost any copy part) should be considered as less than adequate quality. - based on feedback from various forums.

I've really noticed that too. Cavalier parts have become considerably harder to find since lockdown, especially quality parts. Even simple stuff like anti-roll bar links, hand brake cables and tie rod ends which used to be in abundance. Aesthetic parts like plastic trim, interior bits and accessories have always been hard to find (at least as long as I've been in the hobby) but mechanical parts have been easy to get up until now.
All rather worrying really.

Anyway, I replaced my alternator with a Vectra V6 part that has a built in fan. Much more reliable and no need for an auxiliary cooling fan.
I did that because my fan burnt out sometime before my ownership and I couldn't find a replacement.
I do wonder if it burnt out for the same reason that your one stayed on. I shall have to check the relay. I've always had a bit of a problem with parasitic drain on the battery and wonder if that's why.

It's a really complex bit of wiring, and to add to the fun, the circuit with aircon is completely different to the non-aircon.

I used to know it off the top of my head as I done the wiringon aquite a few v6 conversions - where the wiring simply doesn't exist.
The water bridge sensor (brown/yellow) controls the alternator fan and aux water pump. They can run with the ignition off, but to add to the fun, the aux waterpump does not run if the engine is running.

"The water bridge sensor (brown/yellow) controls the alternator fan and aux water pump. They can run with the ignition off, but to add to the fun, the aux waterpump does not run if the engine is running."

Ahh...that's a useful piece of information. Does the water bridge sensor also provide the feed to the dashboard temperature gauge or is that a separate sensor on the water bridge?
I ask because, if it's the former, then normal operation of the dashboard temp gauge would give some assurance that the alternator fan was getting the signals.

The single wire sensor on the water bridge is gauge sensor. on the side, points toward the battery.

The alt fan sensor is really a switch, off/on. All the relays that control them are in the black box at the bulkhead passenger side.