Re: New BPC valve and driver transistors - Saab 9000 Bulletin Board - Saabnet.com
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Re: New BPC valve and driver transistors
Posted by BobS (more from BobS) on Sun, 12 Feb 2012 17:21:36
In Reply to: thinking about buying a new BPC valve but...., SMP, Sun, 12 Feb 2012 12:25:10
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If a driver transistor is bad, you will always get over boost or base boost, the valve can not control boost. A bad transistor is either shorted or open, they fail in that order, although enough current can cause both to happen milli seconds apart. I maintain transistors do not fail unless a coil is shorted or some other short occurred. Do not spark around with anything connected to the control. With the key off, one at a time measure the resistance from the outer BPV connector contacts to battery ground. Be careful with the contacts, do not insert anything thicker than .030" between the fingers, or the fingers can be distorted resulting in poor contact. The resistance should be greater than about 500,000 Ohms (.5 M Ohms). Anything less is suspect. Theoretically a shorted transistor should read near zero Ohms, but this is not always the case due in part to the low voltage applied by the Multimeter and the short maybe to the circuit driving the transistor. To check the BPC valve, cover the center port and blow in either end port, no air should go through the valve either way. It could be you got some poor valves, some of the OEM parts valves would not last long, about what you experienced. A shorted transistor can burn a coil of a replacement valve, so before a valve is replaced, the transistors should be checked.
4.8 Ohms on both coils of one valve is a bit puzzling, the resistance of a burned coil will go up, but with both same, it maybe a meter issue. What is the resistance between the outside contacts?, should be 9.6 Ohms. Other than the 4.8 Ohms, what was wrong with that valve? High resistance on both coils could potentially affect valve function, especially when the coils get hot and the resistance increases.
posted by 71.33.80...
Posts in this Thread:
- thinking about buying a new BPC valve but...., SMP, Sun, 12 Feb 2012 12:25:10
- simple test...., dref, Sun, 12 Feb 2012 19:04:39
- Try cleaning/soaking them, marvinstockman, Sun, 12 Feb 2012 17:29:15
- Re: New BPC valve and driver transistors, BobS, Sun, 12 Feb 2012 17:21:36 <-- Viewing This Message
- Calling Bob S!, Bill Homer , Sun, 12 Feb 2012 13:51:36
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