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Hey guys,
I took out the MAS and it turns out one of the small metal tabs that are soldered onto the ones protruding out of the sensor itself has fallen off.
I have a soldering iron but is it able to be fixed or does it have to be replaced?
That part is never supposed to be disassembled that way. I don't know why Toyota put screws there to sucker people into making that mistake. They should have riveted that connector in place.
Short answer is, unless you are good at electronics PC board repair level soldering, the VAFM (Vane Air Flow Meter, not MAF) is toast. All of the tabs need to be re-attached to the PCB inside the meter (the actual meter is inside the big box, not the little connector you removed.) You'll need to cut off the silicon RTV on the flat cap on top and take the top off. Then it will be obvious to you what really happened.
Easiest to hit up the salvage yard for a complete replacement VAFM (the whole assembly, not just the part you removed.)
Thinking about replacing it, is it best to spend the money on a brand new one or go with one from a yard? Obviously these things have a lot to do with how well the engine runs so any advice here?
Certain brands that make good aftermarket ones or just stick to OEM?
Thinking about replacing it, is it best to spend the money on a brand new one or go with one from a yard? Obviously these things have a lot to do with how well the engine runs so any advice here?
Certain brands that make good aftermarket ones or just stick to OEM?
You are better off with buying a new one, a Denso OEM one and no after market ones.
As far as getting one from a junk yard, I would not recommend it as you do not know how long it has been sitting outside in the elements.
You are better off with buying a new one, a Denso OEM one and no after market ones.
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I'm a big fan of getting new replacement parts when the dollar amount isn't extreme, but a new VAF will cost north of $740.00 http://www.toyotapartsoverstock.com/...225065010.html There are only three parts (the fuel control switch, the air flow rheostat, and the temp. sensor) which you could probably test with a multimeter standing right there in the junk yard.
Of course, the junk yard knows what these go for new, so if the yard wants more than $600 I would have to think long and hard.
I perhaps shouldn't have been quite so negative about fixing it. If you want to try repairing yours, it's probably worth a shot. You don't really have anything to lose but your time. I would consider this an easy repair with a soldering iron, but I've been soldering circuit boards for 45 years and am quite good at it. That being said, these are large traces and easy to get to, so your chances of success are reasonably high.
- Start by removing the whole assembly from your vehicle, clean the outside thoroughly of dust and dirt, and bring it inside to a clean well-lighted work area.
- Cut the silicon RTV away from the flat top (looks like a window but is actually opaque) and carefully remove the top. That will expose the inner workings. You'll see a gear-like mechanism with some springs (leave all that alone for now) and a PC board where the connector you removed comes into the assembly.
- Carefully reinstall the connector body and screw it in place. Guide the broken fingers back above the PC board where they belong.
- Now it's just a matter of carefully soldering all the fingers back in place to the proper nodes on the PC board. As I said, the traces are large and it should be fairly obvious where things go.
- Some traces will likely be stripped from the board. If you can see where they were attached, take small pieces of 24-26 gauge copper (tinned copper is OK as well, but aluminum or stainless steel won't work) wire and solder them across the gaps.
- Test all the connections with an ohmmeter as per the FSM. If they check out, replace the cover and seal it completely with RTV. You don't want dust or moisture getting in to the mechanism.
A word about soldering. For success, follow these tips.
- Get a hot iron of at least 200 watts. Forget the advice to use a wimpy iron to avoid damaging things. Soldering requires heat, and the best approach is to apply a lot of heat quickly, get the solder flowing on the joint, and then get out. If you have to spend longer than 3 seconds with your iron on the parts, your iron is too small or is not clean enough to make good thermal contact. A too small iron requires you to apply heat for excessively long periods of time, and that's when things get damaged.
- Use rosin core solder made for electronics, the leaded kind if you can get it (that's what Toyota used to assemble this part originally). Lead-free solder is almost impossible for a novice to use without special fluxes and tools.
- Heat the joint and let the solder flow onto it. Don't heat the solder and drip it onto the joint. That will result in cold solder joints that will fail almost immediately.
- Get the traces, fingers, and wires bright and shiny clean. Use a wet sponge or rag to wipe your soldering iron tip to keep it clean. It should be bright and shiny as well. Tin it good with a little solder as soon as the iron gets hot, before you apply it to the work. Grungy surfaces don't work for soldering.
- Watch where you wave your soldering iron tip around! I can't tell you how much insulation and how many plastic parts I've damaged by not watching where the iron was pointing when I wasn't holding it on the work.
Thanks for the advice guys. I'm decent at soldering, I just didn't know if, due to the nature of the sensor and how it operates, soldering was possible on this. Ill try to repair it first (whats the worst that could happen) and I'll see how it goes.
They really need to not put screws on that thing like you said RJR. It's very misleading.
I don't think you're likely to hurt the sensor by soldering, at least not if you're reasonably careful. The airflow is sensed by a vane under the spring mechanism, and turned into an electrical signal by a screened-on potentiometer on the PC board. The pot element is big, so it shouldn't be easily damaged. Air temperature is sensed by a thermistor in the airflow, so you won't be near that either. Finally, there is a switch that enables the fuel pump. You'll be able to see that and avoid problems with it. Take your time and you should be able to pull it off. Let us know how it goes.
Quick question, are the small metal tabs that are soldered onto the large metal prongs supposed to loop underneath and contact the main board or are they supposed to sit on top of the prongs they are soldered on?
I don't think I can tell you that without looking at a unit. You should be able to see where the copper has been pulled off the pC board. I would guess it's on top, but again, without seeing it I don't really know.
Do a little web surfing - there are some articles out there about adjusting the VAFM, and some have some pretty good pictures.
This is the best picture I found and it looks like the tabs I am talking about are tucked under the prongs coming out of the plug and contacting the circuit board directly. What do you guys think?
My searching for a new VAFM is expensive. I get mine from the bone yards. I take my Haynes manual or my FSM and a multimeter and with a few quick resistance checks I know if I am getting a good VAFM. Around my area they are about $50 in the yards. When possible, I try to get my parts off of campers. Low mileage and not so many start ups which means lower use on them.
This is the best picture I found and it looks like the tabs I am talking about are tucked under the prongs coming out of the plug and contacting the circuit board directly. What do you guys think?
Starting from the left in the picture, it looks like terminals 1 and 2 go to flying wires, without connecting to the PCB. Terminals 3 and 4 solder to the PCB, 5 has a flying lead and also solders to the PCB, and 6 and 7 appear to be the fuel pump switch which is closed as soon air starts flowing and the vane moves from its rest position. (Now that I look at it, I believe the wiring diagram starts numbering from the right, but you get the idea.)
So I ended up being able to fix it. Was not too hard to do, just tedious soldering work.
So this is what I started with.
As you can see the contacts where the plugs attach to the PCB (Printed Circuit Board) where torn off so they needed to be reattached.
I tried to do it and had issues with the small metal tabs breaking off of the plug so I decided to unsolder the tabs from the metal pieces on the plug itself and attach them to the PCB.
Then I put the plug back in and soldered them to the metal tabs.
All that was left was to test the connections for proper ohm reading.
06-07-2015, 02:09 PM
