Intermittent (Water Heater) pilot won't stay lit

Old 10-27-05, 01:46 PM
Jerry Durand
Visiting Guest
Posts: n/a
Intermittent pilot won't light

I have a Raypak 133-4001 THWS water heater (commercial tankless heater) that's been working fine for a long time. It just started giving a problem with the pilot light.

Original symptom:
The spark was buzzing away, but the pilot wasn't lighting.

There is gas pressure in the pipe (verified by the gas company).
The pilot would light with a fireplace lighter, but the flame seemed small.
After manually lighting it, the flame detector would trip after a bit and turn off the gas.

What I tried:
I removed the pilot assembly and cleaned the orifice.
It STILL won't light from the spark.
Lighting it manually works and the pilot flame is much bigger (and makes the metal plate it hits glow red).
The heater now runs for a full cycle without the flame detector tripping off.

I'm guessing the spark plug has eroded too much to give a good hot spark. Any other thoughts?

Last edited by Jerry Durand; 10-27-05 at 01:56 PM. Reason: clarified subject
Old 11-05-05, 04:26 AM
Sharp Advice's Avatar
Admin Emeritus
Join Date: Feb 1998
Location: The Shake and Bake State USA
Posts: 9,927
Upvotes: 0
Received 7 Upvotes on 6 Posts
Hello: Jerry

Very possible the spark element has eroded too much to give a good hot spark. May simply need cleaning to remove any debris buildup. Or a total replacement of the part.

May also be a weak sparking module. Worn out and unable to produce enough current to create a hot enough or large enough spark. Try cleaning the element first and note any difference. May resolve the problem.

Distance gapping between spark element and ground may be a cause. Most likely as a result of the corrosion build up on the sparking element. Clean all areas with a fine grid sanding paper and blow out the pilot assembly.

Be sure the appliance is turned off before attempting any repairs. Always check for gas leaks whenever a repair includes any connection of a gas part, gas line or tubing or gas supply.

Web Site Host, Gas Appliances Topic Moderator & Multiple Forums Moderator. Energy Conservation Consultant & Natural Gas Appliance Diagnostics Technician.
Old 11-05-05, 08:09 AM
Jerry Durand
Visiting Guest
Posts: n/a
[Grrrrr, I typed in a long reply and when I hit submit, it said I wasn't logged in anymore and deleted the reply.]

Short version:

I ordered a new pilot assembly, same part number as the original (Raypak 020003F).

The new pilot had to be modified to fit.

HV plug was wrong, I cut it off and used the plug from the old cable.

HV wire way too long, cut it shorter.

Kit missing insulating tubing mentioned in instructions, dealer says no kits have it but it is on the parts list. I used tubing from old wire and also high-temp tubing I had handy to protect the much thinner HV wire from sharp corners.

Nut for gas pipe is really long, had to bend the tubing sharply to clear the bottom of the heater.

New design for spark gap works really well, lights on one or two sparks.

Working fine now.

Thread Tools
Search this Thread
Ask a Question
Question Title:
Your question will be posted in: