Hello every one and happy holiday, on my 1991 ctd when it gets cold out and not pluged in my grid heater kicks on like it is suppose to but up till this year ive always heard a high pitch whin,type noies and it would get louder it did this from the time i bought the truck now it cycles but no whine and i dont know if it is working can any one tell me how to check and what to check thank you in advance. does not seem to be working as well if at all you can here the relays kicking in and out

 

Do your headlights dim when the relays kick on? If they do i'd say they are working, if they don't dim i'd say their not working.

I don't have any other ideas on how to test them though.

 

Unhook the thermistor---(air temp sensor)---turn key on and the grids, if working will turn on for the full 40 seconds, then the wait2start light will flash---if that works the thermistor is bad

 

Is this a noise you hear before you start the engine or after? I can hear a high frequency noise from mine before I start it sometimes. I don't know what it is, it's not like there's AC voltage or anything.

 

yes the lights dim and yes it is a high pitch noise ive heard befor starting engine just wanted to make sure it still worked, since i didnt hear noise any more also where it temp sensor? and thanks for your help just didnt want straned and not be able to get it started have a good weekend

 

the thermistor is located just below the crossover--(on pass side), its a two wire connection and its in a hole in the bracket that the dipstick tube is attatched to