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Last week, my A/C blower kept kicking on and off for no apparent reason. Had the 'blinking lights of death' on the ECC control panel. Since the blower powerstage was the problem, I removed it and checked what kind of device it was.
So, after analysing this fairly simple circuit, you can see that the blower power stage is simply a current chopper using a high power MOSFET transistor. This MOSFET transistor is the problem when the unit goes bad.
What does it do? It is fairly simple. The transistor acts like a high frequency switch. Without you noticing it, it turns on and off the blower motor very fast. The amount of time it turns on the motor versus the time it is turned off is directly proportional to the blower speed. This is what they call Pulse Width Modulation (PWM) control.
The problem is, turning on and off a high power motor like the blower motor generates heat. This is why the MOSFET transistor is attached to a HUGE heat exchanger (the 5 big aluminium fins). Why it needs this? It is because MOSFET are really heat sensitive. More your transistor will heat up, shorter will be its service life. So, finally, I think the guys at the development facility chose the best MOSFET they could find back in 1992. But its power rating was not high enough and the huge heat dissipator kept it working until now, making the power stage break after some 10 years of use.
So, what to do to repair it at low cost? Unsolder the MOSFET (It is the only part that is screwed to the aluminium dissipator), find a new one with more that 150W power rating and resolder the new one to the circuit board.
I ordered 3 types of transistors to see wihitch one will work (i assume all will work since they are all rated at 200W and more)
STB100NF04T4 N-Channel 40V - 0.0043Ohm - 120A - D2PAK StripFET II MOSFET
STP140NF55 N-CHANNEL 55V 0.0065 OHM 80A TO-220 STRIPFET II MOSFET
STP60NF06L N-Channel 60V - 0.012 Ohm - 60A - TO-220 StripFET(TM) II MOS
You can obtain those transistors on the internet for less than 3$ or order samples directly from the manufacturer for free (what I did)
I will keep you informed when I recieve them
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Great thread but I'm afraid the bottom line isn't so obvious.
Could you please reply with the best MOSFET (part number) to correct this problem along with the online source so others can get right to the point and order the part? I'm not opposed to ordering directly from you if you like.
Thanks in advance for hitting on a very high interest item.
This repair will allow others like me to save a great deal of money and time.
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the bottom line:
The transistor I used: STP140NF55
The original part: 2SK1423
The form factor you HAVE to specify for your new transistor: TO-3p
and the repair still holds well.
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How did you know it was powerstage problem?
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the blower motor worked if i connected it directly to a 12v source.
So i suspected the power stage which is the only part between the blower motor and the control unit (the control unit seems to be pretty reliable, generally... and expensive to replace)
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I finally recieved the transistors and I will describe here the procedure to fix the blower power stage:
1- remove the power stage from the car (I found removing the metal knee bolster makes this very easier)
2- Open the case. It is stuck together by some plastic clips. Pry them out.
3- Unsolder the transistor. It is positioned a way that you have to unsolder it before taking the circuit board apart. I used some solder wick for that step.
4- Unscrew the circuit board from the case and set it apart
5- Now you see the transistor in all its glory. Unscrew it from the heat dissipator. Be careful, this screw may be stuck hard due to corrosion between the screw and the aluminium dissipator (same issue as the 240 'falling bumper' problem)
6- Apply a dab of dielectric grease where the old transistor was in contact with the dissipator
7- Screw the new transistor, flat side down, as the old one was.
8- Reinstall the circuit board, making sure the transistor legs inserts through the 3 holes you unsoldered. If the new transistor is screwed the same way than the old one, dont bother with the polarity, the legs order is standard for all transistors.
9- Solder the new transistor
10- rescrew the board and close the case
11- Go test it on your car, I recommend you test it with the dissipator fully inserted in the air duct, for proper cooling.
The transistor I used: STP140NF55
The original part: 2SK1423
The form factor you HAVE to specify for your new transistor: TO-3p
(if not, it will not fit properly and you will have to rework the connections, what I had to do with my TO-220 transistors.
I drove the car 2 hours today, 31C outside, humidex 38C, A/C full blast and the repair worked well. So, I would say that it is feasable to repair it yourself.
The picture is a TO-3p form factor. I think it is the size you have to specify to make the rebluid an easier task.
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posted by
someone claiming to be BILLY
on
Wed Jul 22 11:36 CST 2015 [ RELATED]
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COULD NOT LOCATE TO BUY THE TO3P STYLE SO i ORDERED SAME STP140NF55 TRANSISTOR AS YOU USED.
BY REWORK THE CONNECTIONS, I TAKE THAT TO INDICATE THAT THE MOUNTING OF THE TRANSISTOR RELATIVE TO THE HOUSING AND HEAT SINK MUST BE REWORKED. IS THAT CORRECT?
THANKS
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posted by
someone claiming to be Tom Delay
on
Wed Jul 22 22:33 CST 2015 [ RELATED]
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Billy why are you answering an 8 year old post?
Maybe you live 4 light years away? That makes sense.
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posted by
someone claiming to be wyoben
on
Sat Mar 9 09:38 CST 2024 [ RELATED]
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First is this a pay for site , I tried to sign up but it wouldnt let me past the user agreements / second does anyone know anyone who wants to make some cash rebuilding my 850 ECC power stage ...Im at my wits end , they are very hard to locate
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Hi Wyoben, Ben?
Paying is optional at Brickboard, but support is welcome and encouraged.
Try signing up with a different browser.
You might start a new post with a link to this thread, it's some tedious
To find your post.
If all that's needed is to replace a transistor and you can't solder,
search out the nearest ham radio club near you and you'll probably find
someone nearby to solder that and maybe show you how.
Where are you, I can help you find a nearby club.
You'll need a new power transistor and some new thermal paste.
I'm assuming you're in Wyoming. I'd do it but I'm near Boston.
What's the Volvo part number for that unit?
Goto duckduckgo.com (or any search engine) and search for:
"Volvo (part nr)"
Search engines are good with catalog numbers.
Good luck, Bill
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Bill ...A GIANT Thank You for your reply , I've fallen into this " Power Stage " rabbit hole and am confounded ! If I COULD find a new one , I would most likely buy it . I have found 1 used one ...on its way here as we speak , however I would like to have a few extras just in case ...I pulled my old one and I can see some damage ,and I AM A VIRTUAL ELOCTRONIC IDIOT...BUT I CAN SEE IT IT IS PART # 6811581 ... I WOULD GLADLY PAY YOU TO REPAIR IT FOR ME , I WILL PAY TO SHIP IT ROUND TRIP AS WELL .I WANT TO KEEP THIS CAR ,
I DONT QUITE UNDERSTAND THIS PART OF YOUR MESSAGE
Goto duckduckgo.com (or any search engine) and search for:
"Volvo (part nr)"
Search engines are good with catalog numbers.
I use Google and everywhere i search including W/ the updated part nimber ,it shows NLA I apologize for the capitols my caps lock was on Im not yelling , I had my caps lock on , I also apologize for my stream of conscious style of writing I can send you all my contact info , but dont know if I should do it here as it may be public...to be honest with you I am a little confused w/ the BB layout as well Thank you so much Sincerely Ben
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Hi Ben,
That ECC part is 4/31 - "Heater fan power module" - high power switch/relay
Where are you? Maybe there's someone local that can install that transistor for you? I'll help you find a local ham radio contact.
Put up a disposable email address if you're concerned,
or a phone number and a good time to phone you.
Bill
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Guess I must have lost you there Bill ?
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Hi Ben,
I asked where you are, to help you find a local ham to help you.
Did you notice the question?
You indicate you already have a disposable email, Yahoo.
Yahoo, Gmail, MSN all so called "FREE".
Free if you don't mind data-mining corporations scouring your email.
How hard is it to open an additional "Free" account at one of the above scurvy outfits?
You also can put up your phone number and I'll phone you, Is that a state secret?
Bill
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No state secrets here Mr.Bill...anybody that needs to know anything about me probably does anyway ! I use lo budget Yahoo email , and for the life of me got Stymied trying to figure out there disposable e mail debacle ...The Ol Dawg couldnt get it to cooperate ...anyway I dug up one of my Old Ali asses from my state secret days ! If you want to reply to me here I will send you my phone number As I said before , I just dont know about posting my phone number ...I guess its just that Ol secret Agent intuition comin back to haunt me ...Oh and by the way Thank you for your patience in dealing with this mothball subject ...contact me here ... imcashdeniro@yahoo.com and I will send my phone number ...thanxz again Agent 24976 over n OUTTA here !
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Hiya "007"
Did the replacement unit that you ordered fix your car?
Where are you? (I keep asking)
I'll give you a contact to find a local ham radio nerd
that might fix your old module and show you how to solder.
Bill
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Bill...I apologize if this comes thru twice , I didnt know if it came thru as a direct reply ,,, the format of BB has me a little puzzled to be hinest ! thanks Ben
Howdy BillI would like to contact you via more personal communications , but I'm hesitant to put my email in a public forum ? Im not super tech saavy ,so I dont know if that is unfounded , but I was wondering ,since it seems there is no PM capabilities here in B.Board are you a member of any other volvo sites that do have PM ?where we could exchange info in private ...Thank you ...P.S. I tried to set up a temp email in my Yahoo but got Stymied !
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Howdy BillI would like to contact you via more personal communications , but I'm hesitant to put my email in a public forum ? Im not super tech saavy ,so I dont know if that is unfounded , but I was wondering ,since it seems there is no PM capabilities here in B.Board are you a member of any other volvo sites that do have PM ?where we could exchange info in private ...Thank you ...P.S. I tried to set up a temp email in my Yahoo but got Stymied !
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Im trying to figure out a disposable email ...I just dunno if I want to put my regular email out... Thanks for the reply I would like to speak with you ...The Brick Board doesnt have private messaging eh ?
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Great work!! I only remember a tiny bit from the early 80s about transistors but as I recall, the base ("P" of a NPN) is the switch that allows voltage to flow from the N to the other N when the base has a positive applied and thus, the P is energized and opens the gate or turns on the switch as they say. So my question is whether or not frequency plays a role in the MOSFET? In other words, I suppose it can only swith so fast and if so, how do you see that marked on the transistor when you search for one to purchase?
OR... are you saying that the freq is not a factor and you are merely concentrating on the increased power?
With all these going bad, I'm wondering if the MOSFET can't handle the load once the parts get old and/or is heat the reason for them going bad?
By the way, can bearings be replaced in these and if so, do you know of a source?
I truly look forward to the update once you figure this out....
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For anyone who want to check the specs of the original transistor, it is a Sanyo 2SK1423.
spec sheet can be downloaded from this address
http://www.datasheetcatalog.com/datasheets_pdf/2/S/K/1/2SK1423.shtml
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I found this at Radio Shack:
IRF510 Power MOSFET Transistor
N-Channel 60V
Max Ratings:
V-dss 100V
Vgs +- 20V
Id 4A
dm 16A
Igm 1.5A
Pd 20W
I'm concerned that as compared to the original:
IRF510 Pd is 20W but the original lists two ratings:Pd is 2.5W but Pd(Tc=25C) 150W
Also
IRF510 Id is 4A and the original is Id 80A
Are these differences good, bad or indifferent? The IRF510 overall looks to be correct but I don't know this stuff and would like some clarification.
thanks,
Bryan
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Chalk c.f. Cheese.
Phil
--
'98 N/A S70 191500Klm
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OK. Sorry to keep beating this, but I'm looking at the attached url and am trying to make heads or tails of what item best fits what we are doing. The ratings vary and I'm not sure what makes one more appropriate than another.
Could you please look at this and offer your recommendation and I think we'll have this wrapped up.
http://www.futurlec.com/TransMosIRF.shtml
Thanks,
Bryan
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What you are after is a device with the same pin out as the original (refer to the specs of the 2SK1423) with ratings that equal or exceed the original at a price you want to pay. When I say equal or exceed in the case of RDS(on) less is better. In the case of VDSS, ID, PD, TCH,VBRDSS, YFS more is better.
Hope this helps, Phil
--
'98 N/A S70 191500Klm
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What do you mean by "Pin Out?" I'm not seeing this on the spec sheet.
Thanks
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OK so how does this one look. The spec sheet claims correctness.
http://www.futurlec.com/Transistors/IRF1405.shtml
Sorry to seem so dense but this is all greek to me. I just know how to take out the old and put in the new when it comes to this.
Thanks for all the help!!
Bryan
ps. didn't get the chalk and cheese bit...
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Well the electrical specs are good. The only caveat is that the package dimensions are different and that the TO220 package is smaller than the original, however the package leads (pinout) are in the same positions. It won't be a drop-in type of repair as you will have to carefully bend the leads to fit the original hole spacing. I'm sure you will need an insulator under the device as well (a special material that can also conduct heat) also a plastic bush through which the mounting bolt goes, as with the TO220 package, the drain is connected electrically to the metal tab. I note that the TO3PB package is isolated from the drain. If you want a 'drop in' solution and your not familiar with installing such a device, I would keep looking for a MOSFET with the same TO3PB package, as well as good electrical specs as discussed.
Hope this helps, Phil.
--
'98 N/A S70 191500Klm
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Is the TO3PB package older or phased down? They seem to be as rare as hen's teeth!
I'm finding almost all TO-220 and a few TO-262. No TO-P3B.
Another question. I have the Radio Shack MOSFET in hand and it will take a week or so to get the other one online.
Is this a situation where the one I have will just fry? should I not put it in? Or is it a longevity question? It just won't last very long. I want to either put it in until I get the other one or see if I can bypass everything and just run the fan on high until then. We are having 100+ heata index and I need some sort of a stop gap until I get the right part.
Thanks for all the help,
Bryan
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"Is the TO3PB package older or phased down? They seem to be as rare as hen's teeth!" I don't know that - am not up to speed with what packages are available these days, but the TO220 package is ubiquitous I know for sure.
Refer to jean-philippe's statement below.
"The form factor you HAVE to specify for your new transistor: TO-3p
(if not, it will not fit properly and you will have to rework the connections, what I had to do with my TO-220 transistors.
I drove the car 2 hours today, 31C outside, humidex 38C, A/C full blast and the repair worked well. So, I would say that it is feasable to repair it yourself.
The picture is a TO-3p form factor. I think it is the size you have to specify to make the rebluid an easier task."
It looks like he used a TO220 package device without the need for insulators/bushes so you may not need to chase down the TO3P form factor device. Regarding using the Radio Shack Mosfet you have there while awaiting another one, you will fry it in short order. Maybe consider it practice while waiting for the better spec. part to turn up.
Good Luck, Phil
--
'98 N/A S70 191500Klm
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Thanks. I did see that he had used the TO-220. Thanks for all of the info.
I think I'll wait for the "real" one. I don't want to put this one in and have it go almost immediately!! A few more days won't kill me.
Hopefully.
Thanks,
Bryan
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Okay everyone I'm back. Sorry for the time delay. Im finishing a masters degree and I had to complete some laboratory work during the last weeks.
Concerning the compatibility of the transistors, I personnaly checked the power rating, the saturation resistance and the maximum cutoff voltage
If the power rating is too low, the mosfet will heat too much and will fail prematurely.
If the resistance is higher than the one specified on the original transistor spec sheet, the maximum fan speed will be reduced.
If the cutoff voltage is too low, the inducting effect of the blower motor can overstress the semiconducting material by applying excessive voltage to the terminals when the transistor cuts off. This can lead to premature failure.
You can make your fan run full speed by shorting the two terminals of the big connector connecting the fan motor to the power stage. Be sure to use a big wire to short the connector since the current consumed by the blower motor at full speed is pretty high. Make sure that the wire doesnt heat up too much.
Using the 220 form factor, the only thing you have to do is solder wires from the transistor terminals to the circuit board connections. This is necessary because the to220 legs arent long enough to connect correctly to the pcb. Again, the wires you use to lenghten the drain and emitter pins should be at least the same size than the pin itself.
ps.: My repair is still working well!
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I modified the 220 and hooked it all back up and it seemed to start to work and then went dead. From everything I can tell the transistor has good specs.
55V - 5.3 mOhms - 169 Amps - 330 Watts
I have included a picture of the modification. ( If it worked) I cut off the pins from the old transistor and soldered them to the new one. In principle, it is the same thing you did.
There was a bunch of white gunk under the old transistor that I thought was corrosion from time and heat. Is that incorrect? I cleaned it off. Was that wrong?
The new transistor is screwed directly to the heatsink - metal to metal. that is the only difference I can find.
The link for the complete specs for this transistor is:
http://futurlec.com/Transistors/IRF1405.shtml
I have one more transistor and I'd like to hear from you before I try putting it in. I'd hate to burn them both for the same reason. I know the how of these things, just not the why.
Thanks,
Bryan
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"There was a bunch of white gunk under the old transistor that I thought was corrosion from time and heat. Is that incorrect? I cleaned it off. Was that wrong?"
That stuff was the original heat sink compound or thermal grease to make heat transfer to the case better. You need to use this stuff when you install the mosfet, so that heat generated can be better conducted away to the case.
"The new transistor is screwed directly to the heatsink - metal to metal. that is the only difference I can find."
I have a query about that - can you determine if the metal case (of the blower controller on which the mosfet is mounted)is connected to either battery negative (ground) or battery positive? Have you got a multimeter to use?
Phil
--
'98 N/A S70 196000 Klm
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jean-philippe gauthier indicated that he had put dielectric grease on his. I tried that with out a change.
I realized after my last post that the other transistor was also metal to metal. The sink isn't connected to anything else and seems to be non conductive anyway.
Another odd thing. Both times I hooked it up, it started to blow harder (not hard but harder than before) and then slowed down over about a minute. Now it won't come on at all.
I have another transistor in csae this one got fried but I would like to narrow down whats wrong so I don't just fry it too. I'd also like to be able to test the transistor so I can eliminate that as the issue.
Thanks for all your help!!
Bryan
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It apparently hasn't stopped. It's just back to the original very slow speed.
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you apparently did the same thing than me...
if you've put a dab of dielectric grease between the transistor and the heatsink, it should hold up the heat buildup. did you re-inserted the unit in the fan duct before making the test? I think you have to because if not the thing gets very hot very quickly. When i first tested mine, i didnt put it back into the duct and the mosfet unsoldered itself by the excessive heat!!!
if it worked for a short period of time, you connected the transistor right, i think. Did the fan speed changed by playing with the slider on the climate control panel?
I agree that the specs of the transistor you have are supposed to fit the application. But i'm really not an absolute expert with those specifications. Maybe Jorrell can help us with this :)
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You have to search for 'power mosfets' to find transistors that suit this application. And make sure the form factor is TO-220. It is the 3 pin vertical shaped ones with a screw hole to fix it to the dissipator.
On the circuit board, the 3 pins of the transistor are marked S(source), G(gate) and D(drain). The Gate is what controls the 'switch' in this application.
I would only use another power MOSFET here because you have to keep the gate current low to avoid damage to the operational amplifiers that control the MOSFET gate (MOSFETs have insulated gates, keeping gate current very low in saturation mode).
As a temporary fix, I 'borrowed' a mosfet transistor from a non functioning audio amplifier and it works great, proving that the transistor was the broken part. The only thing bad about this is that the smaller transistor heats up like hell and the greater internal resistance, induced by the heat, makes the blower run half of full power at the highest setting. Not mentioning that it will probably blow in less than 1 week from overheating. ;)
I think the fan bearings are not serviceable since it is that sort of sealed teflon lubricant impregnated things. I would try to put some lube on it anyway. It cant be bad.
ST sent me the samples, I should receive it next week. I will post pictures of the operation when I get them.
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Excellent write-up on FET replacements in a PWM application! I am pleased to hear that it resolved the problem. Eventually, under normal operation, if the TO-220 mounting screw loosens, heat will kill the part. There are two other possibilities that will "shorten" the life of a power MOSFET.
1: The gate drive circuit becomes slow, that means that the On/Off pin of the MOSFET is not being driven hard/fast enough. This causes the MOSFET to spend excessive amounts of time in it's "linear" region, this generates massive heat and results in failure of the MOSFET. Contrary to popular belief, a MOSFET is a linear device... not an on/off relay... unless you drive the gate fast enough.
2: If there is a separate exterior "catch diode" on the output of the MOSFET that prevents the negative inductive kickback voltage from the fan motor, the MOSFET will die due to excessive voltage spikes on its output. This is more of a gradual death that blows tiny holes in the insulation barriers of the gate... failure eventually shows up as a hard short or a wide open on the output.
Once again, great write-up... just adding excessive info.
jorrell
--
92 245 250K miles, IPD'd to the hilt, 06 XC70, 00 Eclipse custom Turbo setup...currently taking names and kicking reputations!
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Some great information. When you get it all up and going let us know.
dick
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