Fans are not coming on but the mid and high speeds will work with bi-directional controls and only the passenger side fan works. The blu/blk and the red wire show voltage when back probing (which is the fan that does not work) and when tapping on the fan the voltage jumps all over. I found this by backprobing to make sure I had power, ground and control where it's supposed to be. I may have found a shorted fan but I need help learning to interpret how this fan circuit works.
Did U try the The blower motor resister under the glove box.
I'm not sure I understand how that relates here.
My mistake thought U were referring to the fans in the car passenger side for AC/ Heat !
This should help a bit. Don't get overwhelmed by all the relays and extra wires. Treat each speed as it's own circuit, and then figure out what each needs in order to operate.
Michael I very interested in knowing how this circuit works I notice the relays are setup in different types of relays don't know if you have a understand of the different types, also I saw the grounds on motor one goes throw the relays and the IPDM looks for inputs to turn the relays on and off but this good information �
Just a bit of brainstorming: If you had a shorted fan, wouldn’t you have blown fuse(s)?
Makes sense, amp draw test to rule out a bad motor
I would think so too. Also, showing 8 volts on the blu/blk wire with the key off. How is that not draining the battery?
There should be B+ on the blue/black wire with the key off because the red/yellow wires are hot at all times. It's not draining the battery because there's no path to ground, thus no current flow. Edit: Try spinning that fan by hand with the key off while watching the voltage on the blu/blk wire. I think that's a brushed motor, so if your voltage is all over the place then you have bad brushes…
JC IAM not sure but I believe motor one would have power on (motor one ) with the key off but not motor 2 to being the relays supply's voltage to motor 2 🤔
Yup, I would agree with that. The blu/blk wire is motor 1 though, which is also the suspect fan so I just focused on that motor for the sake of keeping things as simple as possible.
JC how about a voltage drop test at the 40 amp fuse while tapping and spending the fans 🤔
Unplug the fan and test the red/yellow wires with a high amp test light to ground, then voltage drop because we need current flow to properly test drop and the fan doesn't turn on. But considering we get a reaction when tapping on the fan it sounds like an open in the fan motor itself.
Do you have voltage on ground side of motor??? Can not be a ---open---- in motor
Michael said he's getting about 8 volts on the blu/blk wire, and it jumps around when tapping on the motor. So not completely open, but there's something that is affecting voltage happening inside the motor as long as he has good supply voltage.
Ground the motor and prove the theory
Yup, jump that blu/blk wire to ground, should turn fan 1 on even if the key is off.
Supply is good.
So you supplyed a good ground and still does not work ?????
Rodger that JC great input
There is a chance you have a bad connection somewhere... may be even in the backprobe/lead... I would try to rule that out.
I often wonder sometimes. I'm not opposed to piercing provided its sealed up after testing but I don't feel my back probe was an issue. Even with the slightest taps on the fan the meter went nuts.
It is most likely in the fuse box or most likely a faulty box.
So I would assume blu/blk wire is ground and red wire is b+ so if you have power on red wire and power on ground wire wile connector hoked up . Were does your ground circuit go to . ?????
Red is a ground that is only grounded when Relay 3 is activated, red/yellow are B+. Blu/blk is either a ground or in series with fan 2, depending on which relays are activated.
Here is a wiring diagram of that system. I have taken the liberty to add some colors to the different parts of the circuit. This is an interesting circuit indeed. The colors are; Red = B+, Orange = switched B+, Green = ground, and yellow = switched ground. Print out the picture, and that should add some meaning to your circuit. diag​.​net/file/f18exwp9e…
I'm having trouble deciphering your yellow and orange.
That's because I colored it wrong :( I corrected it. Here is a different diagram that is easier to understand. Its all colored with the same colors.
So you have batt voltage at red wire that is ground. Motor should be good . Run a jump lead to this and batt neg . Fan should work . If it does go to relay and jump pin 30 and 87 . I do not have a wiring diagram in front of me . But you can check with test light
First off, those "redrawn" aka Mitchell-style diagrams are usually wrong, so get the OE diagram. But if we pretend it is correct, you see that one fan has two constant B+, and one fan has two constant grounds. Right? Good. So, at each fan, back probe the two wires that are NOT the constant powers or grounds. Now; Activate the fans with bi-directional controls. If the readings change on the…
I did just that with the blu/blk and then on the red wire. Activated it and it changed my readings but no fan operation. On the fan that was working only on mid and high it was doing it's normal thing. Fan is sold as a complete unit.
If fan motor 1 is open, fan motor 2 won't operate on low because it's in series with fan motor 1. Low speed is controlled by fan relay 2, when it's activated power flows through fan 1, through the blu/blk wire, through relay 2, into fan motor 2 and then to ground.
Sounds to me like you have proved out the rest of the system and need the fan assembly then. My local Napa even has it in stock. Way out here in Maui. :-)
I'll come get it but might have a hard time leaving :)