Radiator Thermostatic Switch, Corsa 1.5TD (Isuzu)

[Mark (archive)]

OK just confirmed that yet another Thermostatic swich has gone faulty on my Corsa 1.5TD (Isuzu) 1993 model. I have replaced this switch three times now, and yet again it has failed. If I unplug the connector and short out the two pins, the radiator fan runs just fine, + the fuse is the correct rating. Can anybody give me any pointers as to what is wrong.

I have done the test on one of the newly fitted, but now failed switches. Where you put it in boiling Hot water, and measure the resistance between the two pins, and yep it has definatly become open circuit.

Everytime I have fitted a new one, I have done the test where you let the engine idle, and the temprature gauge has gone up to about 96, then the fan has cut in, and the gauge goes back down again.

I know that most of the time in the UK the engine does not get hot enough for the fan to cut in, all that often (if at all). But here in Spain the ambient temprature is slightly higher, so is more important. I can't get in out of my head (as Kylie once said) that perhaps there is a dodgy batch of thermostatic switches floating about, what are your thoughts??

Mark in Spain

 

[Gary Millar]

OK just confirmed that yet another Thermostatic swich has gone faulty on my Corsa 1.5TD (Isuzu) 1993 model. I have replaced this switch three times now, and yet again it has failed. If I unplug the connector and short out the two pins, the radiator fan runs just fine, + the fuse is the correct rating. Can anybody give me any pointers as to what is wrong.

I have done the test on one of the newly fitted, but now failed switches. Where you put it in boiling Hot water, and measure the resistance between the two pins, and yep it has definatly become open circuit.

Everytime I have fitted a new one, I have done the test where you let the engine idle, and the temprature gauge has gone up to about 96, then the fan has cut in, and the gauge goes back down again.

I know that most of the time in the UK the engine does not get hot enough for the fan to cut in, all that often (if at all). But here in Spain the ambient temprature is slightly higher, so is more important. I can't get in out of my head (as Kylie once said) that perhaps there is a dodgy batch of thermostatic switches floating about, what are your thoughts??

Mark in Spain

If i remember correctly i once fitted a relay and some extra wiring to my sisters astra for this very rerason. The fuse for the fan is something between 20 and 30 amps which is quite a switching current and probably causes the contacts to burn out, especially in a hot enviroment.

 

[Mark (archive)]

If i remember correctly i once fitted a relay and some extra wiring to my sisters astra for this very rerason. The fuse for the fan is something between 20 and 30 amps which is quite a switching current and probably causes the contacts to burn out, especially in a hot enviroment.

I think I have found the problem, after checking the circuit diagram for the wiring, I noticed a resistor in circuit and went on to find out that my model has a two stage fan cooling system, where at a certain temperature, the fan would be switched in via the resistor, and if this subsequently is not enough cooling, and the engine goes on to get even warmer, a second switch in the sensor, switches on the fan without the resistor, at full speed. This means that the switching current is roughly halved between the two switches. I did not notice this third contact when replacing the sensor switch for the first time, and the opel dealers sold me a version with only one switch, ie two contacts (even though I gave them the engine size, make and year), from the outside these switches are identical, and they seem to work, so I have been replacing the switch with the wrong one (three times now). I will go down the dealers this morning and ask for a free replacement, but the correct one.

Just writing this to help anybody else who may have the same problem in the future.

Mark in Sunny Spain.

 

[Mark (archive)]

I think I have found the problem, after checking the circuit diagram for the wiring, I noticed a resistor in circuit and went on to find out that my model has a two stage fan cooling system, where at a certain temperature, the fan would be switched in via the resistor, and if this subsequently is not enough cooling, and the engine goes on to get even warmer, a second switch in the sensor, switches on the fan without the resistor, at full speed. This means that the switching current is roughly halved between the two switches. I did not notice this third contact when replacing the sensor switch for the first time, and the opel dealers sold me a version with only one switch, ie two contacts (even though I gave them the engine size, make and year), from the outside these switches are identical, and they seem to work, so I have been replacing the switch with the wrong one (three times now). I will go down the dealers this morning and ask for a free replacement, but the correct one.

Just writing this to help anybody else who may have the same problem in the future.

Mark in Sunny Spain.

Got the switch changed but I was a bit surprised at the temperature range. 1st switch comes in at between 95-100 and the second 100-105. Sounds high to me, I don't remember seeing the gauge ever go above 96, is this right for a 1.5TD on a 93 plate?????

 

[mikeFNB]

100-105 tis a bit high, but depends on the mixture (anti-freeze etc) use the 95 one, don't forget it changes in a vacuum

mike

i would let things settle now