DIY Blower Motor Resistor Pack Replacement - LotusTalk - The Lotus Cars Community
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post #1 of 169 (permalink) Old 09-12-2009, 05:34 AM Thread Starter
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DIY Blower Motor Resistor Pack Replacement

Over the winter I finally had my resistor pack go bad and decided to replace the resistor pack as i had the front clam off for repairs anyway. As it turns out the $150 dollar resistor pack replacement part is actually about $12 in actual parts. What follows is how to do this if you want to DIY. The whole process took a couple nights to do and was almost entirely the disassembly of everything required to get the blower motor out of the vehicle to fix the pack. The resistor pack is on the bottom side of the blower motor so you have to remove it to get at the packand to do that you need to remove the HVAC airbox first. I wont get into the disassembly of the HVAC parts because its pretty straightforward and has been covered here before. Ill start with the actual repair...
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post #2 of 169 (permalink) Old 09-12-2009, 05:39 AM Thread Starter
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This is the replacement resistor pack and the other pic are the individual resistors. The part is literally just the resistors mounted to a plate but otherwise its the exact same. The resistor values are 0.05, 0.22, and 0.27 ohms at 50 watts and the parts are available thru mouser (Mouser Electronics - Electronic Component Distributor)

284-HS50-0.05
284-HS50-0.22
284-HS50-0.27

They currently list at $4.70 each so thats $14.10 US for all three.
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post #3 of 169 (permalink) Old 09-12-2009, 05:42 AM Thread Starter
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This is the old resistor pack.. As you can see its completely corroded and was obviously mounted in the most ass-backwards fashion. What I believe happened is that lotus sourced the unit for RHD configuration and the resistor pack was to be on top but when they built the elise they moved it to the other side of the vehicle which put it on the bottom.. Dumb.
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post #4 of 169 (permalink) Old 09-12-2009, 05:45 AM Thread Starter
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The corrosion problem is not just one of standing water. As the pics show, even the wiring to the blower had become corroded all the way through and needed to be completely replaced. Oherwise the wiring itself starts to heat up due to internal resistance and the blower runs more slowly. I used 10 gauge primary wire for both power and ground.
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post #5 of 169 (permalink) Old 09-12-2009, 05:47 AM Thread Starter
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The completed wiring was run to the top part of the front of the vehicle. The new resistors were not mounted in the original position as there is no good reason to leave them there. The resistors were instead mounted next to the fuse panel for easy access.
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post #6 of 169 (permalink) Old 09-12-2009, 05:51 AM Thread Starter
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This is the harness with the new wires from the blower motor run directly into the connector. You can disassemble the existing connector and cut the old wiring off of the connector pins and then solder new wires to them. The connector can then be reassembled. This shows the wiring ready for everything but with the resistors not attached. Also note that the fan can run without any resistors if you only care about full speed. (full speed mode connects the orange wire to the blower directly without any resistor)
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post #7 of 169 (permalink) Old 09-12-2009, 05:54 AM Thread Starter
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Below is the wiring diagram for connecting the resistors. I choose to mount the resistors to a small aluminum panel and bolt it next to the fuse block. The wires are simply soldered to the resistor ends. Once everything was completed I actually got much higher airflow from the blower motor because of the larger primary wiring and good connections.
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post #8 of 169 (permalink) Old 09-12-2009, 06:03 AM
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Great report, thanks Rob, much better to locate it where it's at least accessible for when it next goes. If I had to do it I would dispense with the resistors and just directly wire, as I only use #3 position.
Cheers,
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post #9 of 169 (permalink) Old 09-14-2009, 09:17 AM Thread Starter
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Originally Posted by TheViper View Post
Great report, thanks Rob, much better to locate it where it's at least accessible for when it next goes. If I had to do it I would dispense with the resistors and just directly wire, as I only use #3 position.
Cheers,
Michael

no prob... The actual reason that the resistors are there at all is because the blower itself is used to cool the resistors. When you remove the resistor pack there is an opening leftover wher ethe air would cool the casing. That needs to be covered when you move the resistors but i lost the pic that i took. (it was just a piece of ABS plastic cut to size and siliconed in place.)

The resistors are really not necessary: i had it wired just as you mentioned for a couple of months until i got around to putting in the resistors. Honestly the middle setting is totally redundant IMO... you could use just one resistor at about 0.5 ohms for both the 1 and 2 settings and that would give you a slow position aside from the fast one.
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post #10 of 169 (permalink) Old 09-14-2009, 11:41 AM
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I wondered why Lotus placed them in such an inaccessible location, but the cooling thing makes sense. Being in Florida, in the winter I never use the Fan being that the top is off, and in the summer with the hardtop on I only use #3 position which is direct without the resistor. Thanks again for a great informative post.
Cheers,
Michael
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post #11 of 169 (permalink) Old 01-21-2010, 07:25 AM
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Where is the connection to evac the A/C? I'm planning on doing mine this weekend and would prefer to have it evac'd before pulling off the clam.

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post #12 of 169 (permalink) Old 01-21-2010, 08:28 AM
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Where is the connection to evac the A/C? I'm planning on doing mine this weekend and would prefer to have it evac'd before pulling off the clam.
In front of the right rear wheel. Pull the wheel liner and you can get at the fitting - if you look through the side vent you can see them.




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post #13 of 169 (permalink) Old 01-21-2010, 08:41 AM
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cut the old wiring off of the connector pins and then solder new wires to them.
Just a small nit to pic. You shouldn't solder wires in a car - crimped connectors are much, much better - stronger and they don't fatigue crack.

Instead of re-using the connector pins, you can get new ones to crimp onto the wires (a good electronics supply store should have them) that insert into the connectors.




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post #14 of 169 (permalink) Old 01-21-2010, 11:02 AM
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Solder vs Crimped

Tim,

Must beg to differ. A properly soldered connection (no acid core solder, correct temp iron, proper tin/lead mix, etc) with propper strain relief (so the solder joint will not be subjected to mechanical loads) will provide the best electrical connection.... minimum impedance, corrosion resistance, reliability, etc. Soldering a car's wiring harness is not practical, economically feasible or even desirable (due to service issues). Can you imagine how long it would take to unsolder a headlight bulb to change it, LOL. That does not mean for retro-fitting work or special add-ons that soldering is inferior to crimping. Wire wrapping can provide some advantages, in some environments, but not automotive.

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post #15 of 169 (permalink) Old 01-21-2010, 11:13 AM
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Tim,

Must beg to differ. A properly soldered connection (no acid core solder, correct temp iron, proper tin/lead mix, etc) with proper strain relief (so the solder joint will not be subjected to mechanical loads) will provide the best electrical connection....
I beg to differ. A good solid crimped connector is stronger and provides an equal electrical connection to a soldered, with the advantage of being more flexible. There is a reason that car manufacturers crimp all the connectors.

I've also worked on electrical wiring harnesses of equipment being installed in Navy ships (college job), and had to be "mil spec certified" in soldering. All the connections were crimped with a very few exceptions, for those, we had to have very stringent strain relief (loop at the end, and the wire mechanically secured with a clamp).

Now, that is all based on a good crimp connector, and the typical crimper used by home mechanics doesn't do a very good job (the kind that squeezes both sides in so that the crimp takes on an "oval" shape). A good crimper "dents" the crimp into the wire.

If you are worried about corrosion, then you can pack the connector with dielectric grease after crimping and assembling the connector.




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post #16 of 169 (permalink) Old 01-21-2010, 12:03 PM
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I beg to differ. A good solid crimped connector is stronger and provides an equal electrical connection to a soldered, with the advantage of being more flexible. There is a reason that car manufacturers crimp all the connectors.

I've also worked on electrical wiring harnesses of equipment being installed in Navy ships (college job), and had to be "mil spec certified" in soldering. All the connections were crimped with a very few exceptions, for those, we had to have very stringent strain relief (loop at the end, and the wire mechanically secured with a clamp).

Now, that is all based on a good crimp connector, and the typical crimper used by home mechanics doesn't do a very good job (the kind that squeezes both sides in so that the crimp takes on an "oval" shape). A good crimper "dents" the crimp into the wire.

If you are worried about corrosion, then you can pack the connector with dielectric grease after crimping and assembling the connector.
+1
I have to agree with Tim on all of the above points. In my experience with airplanes, you will never find a soldered wire unless it is properly supported for vibration and all crimped connections are made with a go/no go crimping tool that folds and dents the crimp perfectly each time. These crimping tools will make a consistant shaped crimp using the same amount of pressure each time to ensure the proper amount of "crush" for each crimp. A soldered connection, while useful for circuit boards in electronics, should not be used on wires in a motor vehicle due to vibration induced failures.
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post #17 of 169 (permalink) Old 01-21-2010, 01:57 PM
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Can you show some examples of proper crimping tools (preferably affordable for the home mechanic) that work on standard automotive crimp-on connectors. Links to websites where they can be purchased would be nice. I have had problems with the crimps produced by the typical cheap crimping tools.
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post #18 of 169 (permalink) Old 01-21-2010, 05:46 PM
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Can you show some examples of proper crimping tools (preferably affordable for the home mechanic) that work on standard automotive crimp-on connectors. Links to websites where they can be purchased would be nice. I have had problems with the crimps produced by the typical cheap crimping tools.
See my posts here: https://www.lotustalk.com/forums/1209629-post12.html and here: https://www.lotustalk.com/forums/1209693-post14.html for the tool I use. I bought it from an aircraft tool vendor at the EAA Convention at Oshkosh years ago and it cost me $20. There are other styles on the market, but the key is that the forming jaws will not open until they have crimped the connector base with a predetermined force to a predetermined size so every crimp is uniform in size and shape.
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post #19 of 169 (permalink) Old 01-22-2010, 09:18 AM
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The ratcheting crimpers are the the best, but but the price can be a bit high (I just found one on line for $200). But for normal home use you can also get by with a GOOD pair of professional crimpers. I have an old Klein hand crimper, but you can find them at any most any Home Depot or Lowe's. Klein makes professional tools for electricians, so they have them in the electrical tool section.

The Klein crimpers are pretty much a big pair of pliers that allow you to put a lot of leverage into the crimp. The crimp is wide and has the "peg" on once side that dents in the connector to make the secure connection. They really work very well, and they cost around $20. Admittedly not as good as one of the ratcheting crimpers (I have them for electronic connector - old RS-232 pins - so I do know how much better they are), but they do a more than sufficient job.

I the "old days", I used the typical hand crimpers - you know the kind; they crimp, strip, and cut bolts to length. They never did a good job, distorting the crimped connector, and often times having the wire pull out. Not so with the Klein crimper.

Here are two photos of Klein crimpers and a third of a ratcheting crimper. The first is the good kind that I've been talking about. The second is the typical type of crimper that most people try to use - the ones that don't work very well at all. (Note that the photos are not to scale - the first one is bigger and much more heavy duty than the multi-purpose tool in the middle.) The third photo is a generic ratcheting crimper - sells for around $20 (note that it squeezes the crimp but doesn't "dent" it).[/QUOTE]



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Last edited by TimMullen; 01-22-2010 at 09:30 AM.
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post #20 of 169 (permalink) Old 01-22-2010, 08:07 PM Thread Starter
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+1
I have to agree with Tim on all of the above points. In my experience with airplanes, you will never find a soldered wire unless it is properly supported for vibration and all crimped connections are made with a go/no go crimping tool that folds and dents the crimp perfectly each time. These crimping tools will make a consistant shaped crimp using the same amount of pressure each time to ensure the proper amount of "crush" for each crimp. A soldered connection, while useful for circuit boards in electronics, should not be used on wires in a motor vehicle due to vibration induced failures.
This is not correct... Soldering is a superior connection to crimping... the reason why everyone recommends crimping is because soldering takes way too long in for most modern production methods.

The main reason why everyone recommends against soldering is that the solder wicks up the wire and makes the connection prone to vibration failure (or so the theory goes) the only problem is that i have personally seen a solder joint fail from vibration *once*... but i have seen countless crimps fail... even coming off of the $100K tyco crimping machine....


So herein lies the problem... I have the tyco crimper: $500 for the die set and $150 for the frame... If you are going to tell people to crimp because its better then you should qualify that by letting them know that they need a proper crimper... Because if they go and get the $10 crimper from home depot you are doing them a disservice...

Finally, in aerospace where the connection is mission-critical and there is no redundancy, they actually crimp then solder the contact point above the strain-relief with silver bearing solder.
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