Runaway Fan

Reply

  #1  
Old 04-10-03, 06:03 PM
elh23669
Visiting Guest
Posts: n/a
Runaway Fan

Hi
My problem is with my heater fan. I don't know the brand of heater I have, but I'm guessing it's by Sears. The previous owner worked for Sears Home Appliances department and nearly all the other appliances in the house is from Sears. It's a gas furnance approximately 10 years old and has a Hot Surface Ignitor. I've read all the previous postings and my problems seems very similar to the postings of rebnuts (3/4/03) and vcrtape (3/31/03).

First, when I turn up the termostat (Sears programmable model) in Heat mode (fan auto), HSI ignites gas and furnace blows heat. After house reaches programmed temperature, furnace shuts down but blower continues to blow air through ducts. Fan stays on for varies lengths of time, but usually 20,30 or more minutes after furnace has shut off. Sometimes, after it shuts off it will come back on in as little as 2-3 minutes in which case the HSI does not ignite and or produce heat.

Secondly, the only way to shut the fan off(other than waiting 20 to 30 minutes) is to turn off the Emergency Gas Burner switch. Turning the T-Stat off (not down) does nothing to turn the fan off.
I had the HSI replaced 2 years ago, but it's not the problem.
Any hope?
 
Sponsored Links
  #2  
Old 04-11-03, 06:47 AM
KField's Avatar
Member
Join Date: Dec 2002
Location: Easton, PA
Posts: 3,245
Received 0 Votes on 0 Posts
If your furnace uses the common Honeywell combination fan & limit control (I think it is L4064), they had a habit of getting sticky on the fan-off side when they got old. If you take the cover off and watch the dial turn after the burner shuts off, you can see it rotate right back to where the fan should stop and not go any farther. Replace the control. If you have a different style control, forget what is above and try to give us a model number off the furnace or fan control.

The problem is definitely in the fan control, not the ignition circuit or thermostat circuit. You are correct about that.

Ken
 
  #3  
Old 04-11-03, 12:59 PM
elh23669
Visiting Guest
Posts: n/a
I did some digging around with the furnace. It's a Goodman model GMP 100-4 sn# 9306098721. I looked for the fan limiter switch. Following the schematic on the furnace door, I followed two red wires leading from a six wire connector on the circuit board. One wire lead to a small black odd shaped two prong device mounted on the blower housing. A second red wire came off the other prong of that two prong device a went to a multi-wire connector and on to another black device made by Texas Instrument near the Power Ventor Motor. The numbers on it was:
1NT17L-1558
L240F-30
B13700-03
It's about 3"L x 11/2"W. Another red wire led back to the six wire connector on the circuit board.

I don't know if any of this adds to the conversation.
 
  #4  
Old 04-11-03, 01:25 PM
KField's Avatar
Member
Join Date: Dec 2002
Location: Easton, PA
Posts: 3,245
Received 0 Votes on 0 Posts
If your furnace is a downflow, the device mounted on the blower housing would be the high limit cut-out. The other device could be the fan-on time delay. It is doubtful that it would have only 2 wires on it if it is a time delay. Usually they need at least 3 wires. It could be a fan-on thermostat depending on where it is mounted. That would be done with 2 wires. Sorry I can't be more specific but wiring information is not easy for me to get on that unit. It is about a 99% chance that your problem is with the fan-on control.

Ken
 
  #5  
Old 04-20-03, 07:57 AM
elh23669
Visiting Guest
Posts: n/a
Question Chosing Parts


The part number I referred before, turns out to be that of a limit control according to Sears Home Appliances center. With the fan not shutting off after the furnance stop, is that a fan control or limit control failure? It seems my unit is not a combined fan & limit control.
 
  #6  
Old 04-20-03, 08:36 AM
firsthvac
Visiting Guest
Posts: n/a
KField is very correct here. The problem you describe is caused by the irratic operation of one or both of the fan control thermostats (the two pronged devices you described). Turn off the power, remove them...make sure you note which wires go to the terminals, go get equivalent replacements of the same size and temperature ratings, put them back in and check the operation.
 
Reply
Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


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