Back in the spring, my 1987 Carrier Vertical GFA system wouldn't fire
up. I saw that after the HSI didn't come on, it went into shutdown
mode. I figured I'd replace the HSI before fall.
Now, $30 later, the new HSI still won't fire up. The draft induction
motor starts, but no HSI. Could this problem be in the control module?
Is there any suggestion for giving it another DYI repair before I call
in a pro? Any links? Thanks.
You should hang a meter on the HSI connector to read 120V AC before
replacing it.(I keep a spare HSI all the time)
What is error code? If HSI does not glow it is not getting the 120V it
needs on time. Control board may have a cold solder joint due to heat.
Or relay which switches HSI power is not working. In this case it could
be relay itself or logic signal controlling it.
I have a same family furnace here and went thru logic board once so I am
quite familiar with it.
Again, what is error code?
One thing I can suggest you off my head is flip the board over and look
carefully under the two high Wattage resistors to see if the solder
joints is cracked due to heat. I mean hair line crack. Wiggle the
resistors to confirm it. If indeed tha's case, resolder the joint and
drill couple holds around the resistor on the plastic cover for good
cooling. BTW, manual has trouble-shooting flow chart.
Ok, I've been doing some research, and see the next thing to test is
the pressure switch. I've seen some sites that say it should read 24v
across the terminals when the correct negative pressure it reached. Can
I get a clue where the switch is located?
Not really. There are many variables to the sequence of operation of
your furnace, that you need to check.
You can keep on changing parts, until you find out what it is that is
causing the problem, and even after you have replaced everything in the
furnace, you might still have the same problem.
I would call a pro, since furnace repair is really not a DIY repair.
If it was a newer furnace (don't know about 1987 features) I'd first
check that the air filter (cold air return) isn't clogged, check that
if high efficency the outside air intake/exhaust aren't blocked. And
you might try moving the ignitor a tad closer to the flame ... worked
for me with an older gas furnace.
Before you call in a pro, you might want to do some homework..... Consider
that they only build them to last 18 - 20 years. Second, in just a little
over 3 years, the R-22 equipment will not be available anymore.
Instead of screwing with your Jurrasic furnace, you should be looking at a
whole new energy efficient system. Sorry, no, its not gonna be free....but
the new system will most likely pay for itself in energy savings in just a
few short years.
Last hint. You ought to get a trouble code. It fails with HSI not
glowing, then after pause it'll retry and then failing again it'll
give trouble code by way of blinking LED on the board. Then it goes into
lock up mode. To reset you have to turn the breaker off and on.
Checking pressure switch, remove the hose, check the switch with meter
while you blow into the hose(some times debris plug up the hose) Again
consult trouble-shooting flow chart
in the manual. HSI glow sequence comes after pressure switch makes
sensing pressure build up in the flue by inducer motor.
Again, inducer motor runs > presure sensed > HSI power enabled > gas
valve open > flame sensor sneses flame > blower starts running ........
so on and on.
Bye for now.
On 2 Aug 2006 23:49:01 -0700, " email@example.com"
Its very simple. Check for 24v at the module input and 120v at the
ignitor plug. If you dont have 120v at the ignitor plug and you do
have 24v input to the ignition module, the module is bad. If you dont
have 24v to the module the problem is in the safety or control
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