Heater Control Box DIY Repair?
Discussion
My heater control box isnt working. They seam to be £233.83 exchange from clever trevor so I thought Id take a look at it myself first.
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The part number on the burnt out part is BUZ11 and I can get one here for £1.45 (http://cpc.farnell.com/jsp/displayProduct.jsp?sku=SC06473)
Do you think its worth a go soldering on a new component or has the board itself had it because of the heat? The picture makes it look worse than it is, by the way. Is there anyway of checking the board with a voltmeter?
The part number on the burnt out part is BUZ11 and I can get one here for £1.45 (http://cpc.farnell.com/jsp/displayProduct.jsp?sku=SC06473)
Do you think its worth a go soldering on a new component or has the board itself had it because of the heat? The picture makes it look worse than it is, by the way. Is there anyway of checking the board with a voltmeter?
Unsolder the remains of the transistor, and examine the board carefully to see if any tracks are damaged.
If they're not, go ahead and solder in the new tranny.
If there is damage, you can still solder in the new transistor, but replace the tracks with thin wire following the original routes of the burnt tracks. Check both sides of the pcb in case its double sided.
If the damage is caused solely by that tranny running too hot, it might be wise to fit a heatsink to it; However something else might have caused it to pop, in which case the box might still not work.
Heck, for a 1.45 transistor and half an hour's work its worth a try.
Andy.
If they're not, go ahead and solder in the new tranny.
If there is damage, you can still solder in the new transistor, but replace the tracks with thin wire following the original routes of the burnt tracks. Check both sides of the pcb in case its double sided.
If the damage is caused solely by that tranny running too hot, it might be wise to fit a heatsink to it; However something else might have caused it to pop, in which case the box might still not work.
Heck, for a 1.45 transistor and half an hour's work its worth a try.
Andy.
Thanks, good reply. I think its just the coating on the board that burnt. It does have a heat sink which is part of the case. Looks like an after thought by TVR.
Apparently this BUZ11 things is for "HIGH SPEED SWITCHING" suitable for use in air bags. I did know that the speed that the fans turn on was so important.
Apparently this BUZ11 things is for "HIGH SPEED SWITCHING" suitable for use in air bags. I did know that the speed that the fans turn on was so important.
Edited by Work-Shy-Wanabe on Sunday 9th December 18:12
alinton said:
If the damage is caused solely by that tranny running too hot, it might be wise to fit a heatsink to it; However something else might have caused it to pop, in which case the box might still not work.
Both the ones I've looked at the FET's are bolted to a heatsink & also had heat paste on them. I was thinking I'd replace all 3 FET's with relays but never got that far into the job on either car....That level of damage strongly suggests a fault downstream of the transistor. When they fail they most often do so in a short circuit and the result is a fan that runs all the time (hard to be 100% about this without seeing a circuit diagram or at least a close look at a board). Almost certainly an easy fix for anyone with a little electronics experience. I would be delighted to help but with Xmas coming it may leave you heaterless for a while.
Jon
Jon
My guess would be that the high speed FET is used to modulate the on/off time of the current to the fan to regulate its speed, (PWM to the electronics engineers out there).
The best test I can think of and where I would start is to find the hot fan, unplug it and apply 12v and ground direct to it. If it runs OK I would be confident in repairing or replacing the controller. If it has more than 2 wires dont try this as it may have a speed feedback to the circuit. I recently formatted my PC so I dont have the loom wiring diagram to check this.
Jon
The best test I can think of and where I would start is to find the hot fan, unplug it and apply 12v and ground direct to it. If it runs OK I would be confident in repairing or replacing the controller. If it has more than 2 wires dont try this as it may have a speed feedback to the circuit. I recently formatted my PC so I dont have the loom wiring diagram to check this.
Jon
fatjon said:
My guess would be that the high speed FET is used to modulate the on/off time of the current to the fan to regulate its speed, (PWM to the electronics engineers out there).
The best test I can think of and where I would start is to find the hot fan, unplug it and apply 12v and ground direct to it. If it runs OK I would be confident in repairing or replacing the controller. If it has more than 2 wires dont try this as it may have a speed feedback to the circuit. I recently formatted my PC so I dont have the loom wiring diagram to check this.
Jon
I think Ive missunderstood you.The best test I can think of and where I would start is to find the hot fan, unplug it and apply 12v and ground direct to it. If it runs OK I would be confident in repairing or replacing the controller. If it has more than 2 wires dont try this as it may have a speed feedback to the circuit. I recently formatted my PC so I dont have the loom wiring diagram to check this.
Jon
I meant check the board. The pictures above with "HOT FAN" label and the burnt out switch have me convinced that Ive found the problem.
I don't think you need a voltmeter to check the board, the hiroshima colour scheme is a giveaway.
Best way to check the tracks is after replacing the components. you can see by eye what connects to what on the board. Test with a DVM on the resistance range. Any that are open circuit can be replaced with wire links or bridged with solder as appropriate. If you want to do it at home, and lets face it what do you have to lose, I would remove the burned out transistor, clean it all up with alcohol so you can see the extent of the track damage and take it from there. The tranny is off the shelf from RS or maybe even maplin, suggest you change the chip too, its about a fiver (absolute max) and also an off the shelf CMOS 4000 series part. I would think that since the tranny is being directly driven form an output on the chip it may well have taken the chip with it.
If space permits I concur that a heatsink may be a good idea, nice of TVR to save the weight of it, or was it the 10p...
Jon
Best way to check the tracks is after replacing the components. you can see by eye what connects to what on the board. Test with a DVM on the resistance range. Any that are open circuit can be replaced with wire links or bridged with solder as appropriate. If you want to do it at home, and lets face it what do you have to lose, I would remove the burned out transistor, clean it all up with alcohol so you can see the extent of the track damage and take it from there. The tranny is off the shelf from RS or maybe even maplin, suggest you change the chip too, its about a fiver (absolute max) and also an off the shelf CMOS 4000 series part. I would think that since the tranny is being directly driven form an output on the chip it may well have taken the chip with it.
If space permits I concur that a heatsink may be a good idea, nice of TVR to save the weight of it, or was it the 10p...
Jon
Still think you should check the fan itself, you may have found the symptom not the problem with the burned out transistor. That's exactly what would happen if the fan seized or went short circuit. Worth the few minutes checking before you repair the board and plug it back in to be greeted with nagasaki.
Jon
Jon
fatjon said:
Still think you should check the fan itself, you may have found the symptom not the problem with the burned out transistor. That's exactly what would happen if the fan seized or went short circuit. Worth the few minutes checking before you repair the board and plug it back in to be greeted with nagasaki.
Jon
Thanks good idea, will do. Ive been checking the circuits on the board and all seams okay. Jon
Your previous post has lost me some what, if Im honest. There are six chips on two boards of various sizes and part numbers.
fatjon said:
Still think you should check the fan itself
Hot fan is on the passenger side kickwell (you can get to the wires fairly easily) & cold fan is on drivers side.Not 100% sure on hot but cold is just a 2 wire fan.
Also if you search there is a link to the wiring diagram on here.
aaah, the CMOS 4000 is the closest and next/previous chip in the curcuit. Numbered MC14504BCP, I'll order one of those too. By the chip do you mean the big one, has heater written on it in pen. (this one http://www.futurlec.com/Microchip/PIC16C57.shtml)
Thanks for your help.
Thanks for your help.
it's actually a generic 4504BCP which is a 4500 series cmos chip. The MC1 prefix means it's a motorola version but many manufacturers make this series of chips. The BCP suffix is important. I suspect that the B in BCP means buffered, ie either a high current input or output stage which will matter.
Jon
Jon
You dive into the passenger footwell, pull the carpet covered end board out. Remove thje various control boxes that fall out noting connections. Then rummage up behind the leather covered scuttle trim over the footwell on the lefthand side to find one wing nut - undo that and a pozidrive screw on the righthand side by the knee vent, then the scuttle panel should come down and out.
Next remove the carpet from the left side of the footwell, untape the looped door release cable and you will see several lines of gaffa tape which are covering the edges of rectangular fiberglass panel. Burried under the tape are several small pozidriv screws. Undo those and a couple of large screws that hold the motor bracket and the panel will come away revealing the motor and box containing the heater matrix inside the cavity in the nearside wing, and in my case no less than 3 carrier bags full of dry leaves!
To unsieze the motor I ended up partly draining the cooling system (syphon out of the radiator drain plug) then disconnecting the two hoses to the heater matrix, the hot air duct to the dashboard and the electrical connmections to the motor then removing the air box with motor attached. That way I could separate the blower from the box and unsieze the motor properly. Reassembly is the reverse etc etc.
It isn't as big a job as it sounds - honmest!
Next remove the carpet from the left side of the footwell, untape the looped door release cable and you will see several lines of gaffa tape which are covering the edges of rectangular fiberglass panel. Burried under the tape are several small pozidriv screws. Undo those and a couple of large screws that hold the motor bracket and the panel will come away revealing the motor and box containing the heater matrix inside the cavity in the nearside wing, and in my case no less than 3 carrier bags full of dry leaves!
To unsieze the motor I ended up partly draining the cooling system (syphon out of the radiator drain plug) then disconnecting the two hoses to the heater matrix, the hot air duct to the dashboard and the electrical connmections to the motor then removing the air box with motor attached. That way I could separate the blower from the box and unsieze the motor properly. Reassembly is the reverse etc etc.
It isn't as big a job as it sounds - honmest!
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