clare chu9o gas furnace

[buzz]

i have a customer with a clare chu90 gas furnace,pressure switch was sticking open,replaced with new aftermarket part,new switch closes,hsi lights pilot,burners turn on and instantly go out,tried several times,same thing,thinking it was a faulty pressure switch losing pressure at ignition i replaced it with another new one,same problem.blew in old pressure switch a few times and it is still working,for how long i don't know.lots of draw at pressure line and the replacement parts are the same pressure?
has anybody experienced this before?

[The Builder]

Return that part and go to a plumbing/ hvac supply store and get the same one that works

[buzz]

two faulty switches,that's possible,same manufacturer,same supplier.i might try another supplier