[Clyde71]

My first question is, I was working on a rudd deluxe 90 plus that was not igniting...more like spitting. I checked the gas valve and I was getting 24v, the hot surface ignitor worked. I checked the coil on the valve and it showed it was open..O.L. Doubled checked the gas pressure going in and coming out and they were ok. I looked at the board and there is a burn spot on it, so I went back and double checked that I was getting continous 24 at the gas valve..and that checked ok. So I replaced the gas valve based on my O.L reading and I did take the wires off to check. I still have the same problem and Im getting the same O.L reading on the new gas valve.Also can the hot surface ignitor also be a flame proving switch? There are only 2 wires for it, nothing else to prove the flame.

So is it possible that maybe the board is cutting in and out fast enought that my meter is not reading it?Is a hot surfac iginitor a proving switch?Is my meter bad (fieldpiecesc67)I double checked with a resistor and was close to the resistor reading. And what am I missing on the gas valve that Im getting a open reading!? One more thing the gas valve is a robert shaw 7200...only 2 wires and a ground that is connected to the board and I do have continuity with that.

Thanks a million guys

 

[bzzline]

O.L. might be over current reading I looked at a wc meter did not see "ok" on ours.

 

[Clyde71]

O.L. might be over current reading I looked at a wc meter did not see "ok" on ours.

open reading and no there is no "ok" on mine either. I guess I should have stated that I had the factory recomended pressure readings.

 

[Paul Bee]

Get your posts up to 15 and apply for Pro membership. Since you have a fieldpiece meter and your epa universal card i'm gonna bet you are a repairman.

 

[surenuff]

Do you mean you checked gas pressure coming in and out of the gas valve? How do you get a pressure reading on gas flow thru a valve with a open coil that won't open????

 

[SBKold]

I did work on a Rheem Furnace that must have used the HSI as flame sensor as well.

In the flame unit stayed lit....take HSI out and flame goes out.

Not real sure how it did this but I will post this question in the professional forums.

 

[Clyde71]

Do you mean you checked gas pressure coming in and out of the gas valve? How do you get a pressure reading on gas flow thru a valve with a open coil that won't open????

The pressure reading I was getting was fluttering, when I checked the gas coil itself for resistance I was getting a open reading. Thats why I had a few questions. The new gas valve was getting an open reading as well and the furnace is having the same problem, thats why I asked about gas valve readings and why Im getting them (what are the chances of having a bad new gas valve)? or is my meter messed up? A friend stated that the hot surface ignitor is also a flame sensor, but one of my other questions was is it possible that the board could be bad or good enough to send 24v to the gas valve but not constantly to where my meter wont read it? There is a burn spot on the circuit board around a resistor, thats why im asking the previous question.

Also Im wondering if the hsi is a flame sensor, I should be able to get a reading if I put a flame to it. So I took a torch to it and hooked my meter to it and set my meter to dc and got 1.2v. Would that be the correct way of testing it?I also checked for ac volts and got nothing.. I dont think my meter would be able to read microvolts if the hsi produced it. It does not look to have dismilar metals to produce current, but it appears to have ceramic or similar material for the body. any thoughts?

Thanks

 

[Clyde71]

I did work on a Rheem Furnace that must have used the HSI as flame sensor as well.

In the flame unit stayed lit....take HSI out and flame goes out.

Not real sure how it did this but I will post this question in the professional forums.

Thanks I really appreciate it. And if you could find out why I would get a open reading on my meter. Both the new and old one read the same. Also just for some more info I tested the coil with the continuity tester and it showed it to be ok..so my thought are that the resistance reading would be more senstive, but I starting to wonder..is my meter crap?

 

[SBKold]

See if the resistance changes with heat

 

[surenuff]

chances of two bad coils is slim but not impossible. I like to isolate ciruits when I test for continuity or voltage. have you checked for 24V at the lines to the gas valve with them unhooked? and did you check for conituity or resistance with the wired unhooked?

 

[SBKold]

you have it on the continuity scale?

You may not have your meter on the right scale. 200K?

 

[Clyde71]

chances of two bad coils is slim but not impossible. I like to isolate ciruits when I test for continuity or voltage. have you checked for 24V at the lines to the gas valve with them unhooked? and did you check for conituity or resistance with the wired unhooked?

I didnt check with the wires unhooked when doing voltage, and the other tests, yes the wires were disconnected.

 

[bmathews]

If you have a burn spot on the board. That would be the first thing I fixed before I started changing parts out. Why would you even proceed before fixing a burned circuit board? That board controls everything. It could be dropping out voltage, not sensing the flame or any number of other problems that is causing yours.

 

[surenuff]

I have seem more than one board that had a burned spot on it from a prior problem, but board still worked. I seen it on boards where I fixed a bad fan relay or condensor contactor, replaced fuse and went on down the road. Board shoul only be changed if we make sure the board is not working. Or, we are just parts changers.

 

[Twilly]

Twilli says http://www.youtube.com/watch?v=mRadA7074wk

 

[bzzline]

If the field meter is ok, ( leads may not be contacting the coil terminals) and the control board is ok (just a little burned around a high watt resister), purge fan or vent motor ok
I would check for condensation water in gas supply line.

 

[SBKold]

Looks like yes, the HSI is the flame sensor on this furnace.

There may be an upgrade kit to retrofit to a flame rod sensor.

 

[Clyde71]

If the field meter is ok, ( leads may not be contacting the coil terminals) and the control board is ok (just a little burned around a high watt resister), purge fan or vent motor ok
I would check for condensation water in gas supply line.

The inducer fan works,hsi works. I didnt think about condensation, if there was would there be an accumulation in the trap?

 

[Clyde71]

Looks like yes, the HSI is the flame sensor on this furnace.

There may be an upgrade kit to retrofit to a flame rod sensor.

Thats what a friend told me...so to test this, could I put a flame to it to get a reading? Would it be ac or dc? I didnt see anything in the schematics about it either being a flame sensor nor if it would be dc or ac for the flame sensor.

thanks

 

[SBKold]

It is the flame sensor and the board utilizes some kind of technology to use a standard HSI as flame proofing. How to test this all this is still a little beyond me. Just try a fresh one one of these is about the best way.