Hope not. That would be a new PEM...Some kind of failure in the driver(s) such that it (they) can deliver 12V unloaded but not under load?
Yep. I may try an even lower wattage bulb, perhaps an old 12v panel lamp if I can find one in the junk box. At some point, it's got to work.And yet, the PEM output measures 12V unloaded?
Yes, quite familiar with Ohm and his friends. I specifically challenged Tesla on the connector last Fall, and I am just reporting what they claim. There was a visual inspection, as well as a "pull test" to verify the pins were properly mating. I do suspect the connector, especially given the current this thing draws at maximum. Do you (anyone?) know what the actual draw should be at 12v, if that's what the PEM is trying to push into it?It really helps to remember Ohm’s Law when diagnosing with a multimeter. Just because you measure 12 volts with the meter does not mean that you will have enough current to drive a motor (or lamp). If the connection has an impedance of 120 ohms you could only push .1 amps through it. Measuring 1 volt at one side of the motor tells me that 11 volts are lost across a resistance. This of course assumes I understand how you placed the meter leads and that the PEM was trying to drive the motor. Many people have reported the fan connector problem and many times it is reported just after a visit to the service center. Myself included. Just because a technician said the connector looked fine (to them) doesn’t really mean much. If the motor is OK then the next most likely culprit is the connector under the PEM. It would be a shame to spend thousands on a rebuilt PEM if it is just the connector.
Yeah, this is what I was thinking. I'd strongly prefer not messing with (unhooking) the HV wiring. Is there enough slack that I can unbolt the PEM and raise it up on the passenger side? I think there just the big bolts in the back (one on each end) and the two smaller screws on each tab. Anything else?You need to look at the connector. Unbolt the PEM and raise it up, or take out the wheel well liner to get at the connector.
Hi Jason,so when you charge you don't hear the fans underneath the pem or the rear of the car turn on? you just mentioned "when you wake the car up" this means the car is going to sleep and battery / pem is achieving temperature to state of idle.
Do you have ovms? is your pem still reaching 62c? and what about battery temps?
When you wake the car up there is also a Fan inside the PEM you should hear as well; like a pcboard fan - do you hear this along with the coolant pump running? you can even feel the pem vibrating from the pcboard fan.
View attachment 559817
Yes, you could reach the board mounted connector that way but you can’t get the connector or the board out because it is screwed to the PEM from the bottom.3. Can the PEM cover be removed (to access the board with the bad connector on it) without removing the entire PEM from the car? I see a number of screws on top that might be accessible.
1. What is the proper draw from the blower motor at full power? Through a long cord (to introduce some resistance), I see it drawing about 8.6 amps at 7.8 volts. I can't currently measure it at full power, as I don't want to jeopardize my meter. The implication here: if the motor is drawing excessive power, did it cause the connector to fail and should also be replaced?
Thanks for this! I was thinking PowerPoles too, though they're not especially weather or vibration proof. How well do they hold up?It sounds like the PEM controls the ground to operate the fan, not the positive. Your voltage reading upon wakeup would comfirm this, unless the PEM is already hot and calling for the fan to operate. That and the grounds should be connected to ground at all times if the positive was controlled. Both positives would be connected to the APS output inside the PEM, and have exactly the same voltage. The original dual motor setup used two separate circuits, which are now operated at the same time, and connected to the same terminal on the single fan motor. Apparently the single motor used less current than the total of the two original motors, so connector life is increased. If I remenber correctly the CFM of the single motor is less than that of the total of the dual motor setup, so the only reason for the "update" would be to prevent the connector form burning up. You need to check the connector.
You can raise the PEM up enough to get at the connector, but you will need to disconnect the three orange motor leads on the PEM thru the access panel in the trunk. They do not have any power unless you are trying to move the car, so just make sure the key is off.
You can get the wheel well liner off by working around the wheel, but it is a lot easier with the wheel removed.
I used some 30A anderson conectors with a pigtail soldered direclty to the PEM terminals, and permently fixed the issue.
Thanks for this! I was thinking PowerPoles too, though they're not especially weather or vibration proof. How well do they hold up?
The data on wake up with a cold PEM and traction motor (24C) still shows +13.4v being sourced by the PEM. I don't know from which side (PEM fan or Motor fan), given the bridge between the two sides, but it's clearly trying to spin the fan even when cold. Given that the difference in the negative side is only a few mv, it seems like it's both sides that are being so driven. This was a bit of a surprise. I wonder if it's because of the prior 1144 / 1146 alerts.
To solder on a pigtail, I presume I would need to remove the entire PEM from the car in order to get at the screws on the bottom. Or, with the 3 motor wires removed, will the PEM "flip up" on its two main supports in the back (towards the front of the car) if I just undo the 3 screws at each end? It almost seems like it was intended to do this.
Alternatively to making a pigtail, a thought... Presuming that the PEM connector itself has been damaged along with the cable going to the fan motor, would replacing the connector with a stock unit AND bridging the two positive pins together inside the PEM make it robust enough to be used normally? I'm a bit puzzled that all the pictures of damaged connectors seem to be on the positive pins only. Electrically I don't understand this, but if that's "expected", would bridging them inside the PEM be the proper way to prevent the failure from recurring? Keeping the PEM looking "normal" would prevent Tesla from refusing to work on the car.
Can the car be charged with the 3 motor wires removed, but everything else connected? I thought the motor was part of the charging circuit, or was that only on the 1.5's?
Sorry for all the questions, and thanks for your help!
Thanks, and yes, I've already studied your post. Excellent work.I actually just went thru this with my car. I dont know if I would BRIDGE those two together as if one is powered and the other isnt, it might cause an issue with the PEM.
I ended up for now replacing the connectors. As @PV-EV noted, you need to pull the whole pem to replace the connector as its screwed on with 2 torx screws on bottom.
My connectors and plug were totally fried,
Fan didnt operate at all with this level of connector damage.
I pulled the pem and the 2 boards that are required to get to the CIC board which has the PEM Fan connector.
The right most connector is the PEM FAN one.
clean out the old solder holes carefully.... no drilling! just a solder vac and they blow out easily
after the work was done.
Its not that hard to do, just takes a little solder skills and a few hours to pull the PEM, replace the connector and put it all back together.
lots of screws and little parts to keep track of where they all go... but its doable.
Check out my post
PEM FAN Connector pin identification
which has a little more info and schematics for the two motor and fan lines.