cab heater fans not working.

[shadygrove69]

I have a Zetor 7745. It has a heater for the cab. We have had since it was new. The heater fans have always been a little testy but now only one works and only on one speed - high. We have tried new relays like a older mechanic recommended and that didn't seem to work. He said something about having them in sequence when installing. We did that and it didn't seem to make any difference. We know some of the wiring up where the heaters are actually located needs replacing but right now it isn''t a problem since we have it broken down and working on it. Help would be greatly appreciated.

 

[6745 driver]

I am not sure how the fan speeds are controlled on the tractor but in most cars the lower fan settings are controlled with resisters and when the resisters fail the only speed left is high.

 

[zjakopovic]

Very often 2 speed DC motors have 3 brushes.
Two of them are on opposite sides, say up and down, and 3rd is 15-30 Degreeson on side, out of brushes line, let say on top.
Bottom brush is "-" pole, top one "+" of lower speed, and side one "+" of faster speed. This kind of motors have 3 wires out of them.
If is speed regulation done on way like this, problem is with switch, wire or brush.

If is 2 speed meke with resistor, then resistor can be a problem. This kind of motors usually have 2 wires out of them.

Hope this helps

 

[alan]

The brushes wear on the fan motors to check this out link a 12v supply directly to the motor if motor fails to run replace complete motor.

 

[brian_lofthouse]

Ive use to have the same problems with the heater fans in our 7245, untill I found they are the same as used in the old Skoda Estelle. So I replaced them with two out of a scrap car.
WD40 oil helps and a good bang under the heater if they stick.
Brian.

 

[markku]

Case-Poclain excavators has fan in some models. this can be fitted to Zetor cabin very easily! It works 4 times longer than original zetor fan.

But

You can buy 10 zetor fan what cost 1 case-poclain fan.