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Old 07-07-2003, 12:01 PM
Arthur Dalton Arthur Dalton is offline
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Join Date: Aug 1999
Location: Florida / N.H.
Posts: 8,784

The reason for your NO Fan on ETC sensor test is the same as your No fan a/c ...
The fuse feed for the coil side of both relays is common in the fuse box..
The load side for each fan circuit [ relay secondary circuit] is the Contactor side of the relays. These have seperate load fuses.
So, if you have a bad fuse / connection on the relay coil
side [ primary side], No fans will work [ low /ac fan OR ect/ high fan.].
This fits your remedy/cause diagnosis.....
Bad contact on relays primary circuit feed ..

Just remember ... the sensors trip the COIL side of the circuit .
This is the low amps/current side of the relays
The working. high amps [LOAD] side of the relays are the CONTACTS in the relay and they carry the high current to the fan motors... [ that is why we use relays] --low switching/sensor current used to pull-in contacts that are capable of carrying larger current [ in this case , fan motor...]
A tip off to a tech as to wether the problem is on the relay coil side is to listen for the relays to CLICK when testing the sensors ..if a relay is clicking and one still has NO fan, one knows that the problem is not on the relay primary side of the circuit..
so you go to the load side for further testing ..[ usually fuse on load side for high fan and good chance of bad dropping resistor/connection on low [a/c] fan......
As you already know, the most common mis-diagnosed NO low a/c fan is the fact that LOW freon level will not allow the high
side pressure to reach the switch cut-in , anyone getting a fan after jumping sw. test must first check freon level/pressures before condemning the sw......
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