That's because (if my memory serves me correct) the left blower on the dual blower upgrade (on the bottom) blows air up into the PEM, the right blower blows into the electric motor's cooling fins. I also believe they added another cooling fan up in the PEM. All this was done only after the dual fan/blower upgrade which the 2.0s didn't came stock. I believe Tesla only began putting two fans/blowers in the 2.x PEMS after identifying a cooling issue. I don't know where that cut-off is. And the previous design the single lower blower was trying to cool the motor down as well as force air up into the PEM.
Where as the 1.5 PEM there's only one fan (really a blower which is stronger) that doesn't get or need any assistance from the (motor cooling) blower down below. This blower is only dedicated to the electric motor. Menlo Park also confirmed that the 1.5 doesn't pick up as much dirt and grime from the road since the fan air pickup is right at the PEMs base, which still picks up ambient dust that adds up to dirt, but not as much or as heavy as force fed blower where the pickup is at the lowest rear part of the Roadster which gets the brunt of dirt / dust / leaves / twigs kicked up by the front wheels and underbelly of the car. Look at any video or picture of a 2.x getting cleaned out, its rather disgusting. The pick-up tube also should be cleaned and actually washed with fresh soapy water for a true cleaning, but the Rangers/Tesla doesn't do that. I don't even know if they blow the duct tube running from the lower blower up to the the PEM out.
From my analysis of searching the forums it appeared to me that the majority of the PEM failures were from 2.x Roadsters so if the survey indicated that the majority of failures came from 1.5s I have to disagree by the design of the PEM/Cooling as well as reading the posts on PEM failures and identifying what version of Roadster they were linked to. (granted there's approx. 500 1.5's and 1,950 2.x's in the world) To me, Tesla may have tried to address cooling the PEM better, but also had to reduce costs. Someone came up of piggy backing off the lower blower to get more airflow over the PEM bug ignored the fact that that's the worse place to pick up clean air. I'm sure their testing showed that this was a bad idea, there are tests showing the roadsters doing doughnuts in a dry dusty / dirty field. But they were under the gun again for delivery and stuck to it. When customers complained, they offered a dual blower setup, but that just forces more dirt up there faster into the PEM! Yes it does cool it down nicely but its still in the wrong location. If I owned a 2.x with the dual blower I'd find some way so that blower pulls fresh clean air from a high location, not low. And yes, we do hear that the 1.5 was built like a tank over and over again, reason being is that Tesla was not in cost savings mode but rather in proving ground mode. They put parts in there that were aircraft quality and more robust so that things would have a lower chance of failing. It looked and looks and feels like a quality component when opened up. When cost savings came into the picture the 2.x PEM took a hit, and a cheaper way to build it was applied. Not only cheaper in making, but cheaper to service. Hence allowing the Ranger to remove cables from the PEM from the top of the PEM and the front of the rear cargo bin. The faster a Ranger can service a Roadster, the more cars you can service for a given technician and more money you can make. People (in the forum) who've had their PEMs fail in their 2.x's felt like inferior parts were put in there and that was the root of the failure. I also came across a couple 2.x owners who had their PEM replaced twice as well as 3 times! Don't know why, but it sounds rather odd. I haven't seen a post yet of a 1.5 PEM being replaced that many times although there could be one. But I doubt it.
I feel confident in my 1.5 PEM and I'm already a year out of warranty. I'm doing my own PEM cleaning / maintenance here in a week or two and will be blowing the PEM out as well as the electric motor's cooling fins and cooling blower. Never had a switchpack issue and think if that would have went, it would have kaput already. My battery was replaced under warranty at 14k due to a problem internally with the 12v aux. power supply which is housed inside the main pack. Nice not having a 12v battery that runs dead, but then it makes the problem more complex if something fails. I don't see that failing again and happy Tesla covered it. Actually really happy my pack was replaced as I saw two sheets that were pulled down and way lower in capacity than the rest. My new pack is very healthy now and feel very confident with it. I also know how to treat it well, cool-downs, don't push it hard when below 50% SOC, keep it out of the hard sun during the summer, and target 50% SOC when sitting as much as possible. One thing to note is that when Tesla does a bleed test is that it does not show the full health of the pack. You can have sheets that are way lower than the rest and it will pass the bleed test fine. Bleed test just shows the pack can take a charge and discharge without an issue. It won't tell you if a sheet is dying due to a bad brick or cell unless its catastrophic. What Tesla has but doesn't show or tell you is a program that plots the health for each brick in each of the 9 sheets! That's the information that's key in REALLY knowing how healthy your pack is. You can see what sheets are pulled down and which ones are giving you a weak CAC value. And the only way to get this info is to become good friends with one of the engineers. Really wish this was a public diagnostic tool but ohh well.
At 28k I feel my Roadster has settled in pretty well and if something does come up I'll address it myself or if I don't have the tools/expertise I do have the connections that allow me to get it done properly without any need for an extended warranty.
