I have a Rheem 90 plus furnace. It cycles to the end but the flame shuts off before the fan comes on. It does this for both attempts. The 2 green indicator light are solid state no blinking and no amber light during the entire process. Any Ideas?

The problem is most likely to be a defective fan limit switch. Here is link to a video that describes how to replace it Rheem Furnace Fan Limit Switch Replacement 47 22860 01

It sound like the limit switch is shutting off and not coming back in to play .

Check condensate water /drain stopped up. It will allow a start after a reset but then it shuts the combustion air fan down and that shuts the unit down this will require a service tech make sure their familiar
with 95% units

Your inducer motor is bad .that is the small motor that is connected to the pvc and with a hose attached to it.
That is the first thing to come on when unit calls for heat.

Hello bikejocky,

MOST LIKELY you have a "hot surface" element
with a tiny crack in it...
About 25 years ago... I put one of my poor abused
fingers on the element to see if it was at all warm...
In so doing I touched the spot where the crack was...
and it did INDEED have a full 120 volt, 60 cycle AC
current waiting for my FINGER to complete the
circuit... (not a recommended procedure)

My 25 year old RHEEM... finally kicked it.
I keep spares... and bought 2 more when I used
the last

Since these parts are pretty cheap... I get spares
62 22868 93 Rheem 62 22868 93 Hot Surface Ignitor

Take a look... There are two basic configurations

The WISEST APPROACH is to use a "meter"
to verify the "line current" is present (not finger)
and check the "SURFACE" for continuity.

Once you copy the number DIRECTLY from
YOUR OWN part... look it up... internet... eBay
and AMAZON (like Robert Shaw #41-408).
http://www.ebay.com/itm/ROBERTSHAW-41-408-Hot-surface-ignitor-NORTON-271N-/121727955205?hash=item1c578d3105:m:mJR3I8e9mTI60A-dtmvdVrw

>> It is the plug & mount that is important...!!

(consider that spare you always wanted
(If you get it... you will probably never need it)).

~~

The cycling limit & fan
(never touched a RUUD... (so... I presume)) is to clear accumulated GAS FUMES to avoid any explosive
situations.

I do know RHEEM... (ERGO... I have every confidence)
((RHEEM & RUUD, in my opinion, are design twins)).

Carnac the Magnificent

Check the draft inducer air switch ( vacuum diaphragm switch) If the switch is opening when the burner starts, you might have a blockage on air piping coming into the furnace. Also prime the condensate trap on the condensate drain from the combustion fan. Also check the gas pressure, if your gas pressure is dropping, the gas pressure switch will shut it down. If it's too high the moment it comes on could raise the pressure in the furnace dropping out the combustion fan proving switch.

Trunthe fan from the automatic position to the on position, if the blower does not come on then you
might have a relay problem. The relay is built into the
board, you may have to replace the board.

Sounds like it could be a dirty or bad flame sensor.
When the burner lights ,there is a flame sensor in the flame and it is suppose to sense the flame and send a signal back to the control board which will keep the gas valve open, if it gets dirty or is bad it doesn't send the signal back to the board and the board will shut the gas valve off and after three tries it will lock out the furnace and you have to reset it to get it to work again.
The flame sensor looks like a wire and it's in the flame usually it will get gas deposits on it, then it won't work.
You can clean this sensor with an extra fine piece of steel wool, but before you attempt to do this DISCONNECT ALL POWER TO THE FURNACE.

flame rod sensor

If the burners do not fully ignite, the sensor will shut the furnace down. The lack of sufficient burner flame is a gas valve or gas pressure problem within the valve.
Replacing the gas valve with the original one may get you going. I surely suggest a professional service company for safety reasons and a thorough inspection. A 20 year old furnace is past it's normal life span.