I have a 2 story house (bought 6 years ago) with two Snyder General Comfort Maker heating and cooling systems (a larger one for downstairs and a smaller one for upstairs). The furnace units are in the garage and the condensers are outside. The systems are over 20 years old and need to be replaced, but I can't afford that right now. I haven't had the units serviced in the last 6 years and I don't know if or when the previous owners ever had them serviced.

I am having problems with the smaller upstairs unit:

Condenser Model: AC018GB (mfg 1990)
Furnace Model: GUD040A012AIM (mfg 1990)
Digital Thermostat

I have the original installation and operating procedure manuals with the wiring diagrams but they are somewhat greek to me. I can sort of follow what is going on. I can scan them if needed.

The problem with the unit is that nothing happens when I turn it on. If I change the t-stat fan switch from Auto to On the blower does not turn on. If I switch the t-stat to AC and set the desired temp low enough to turn on the AC I hear the click in the t-stat but nothing happens. The blower doesn't turn on. The outside condenser doesn't turn on.

Would a bad 50E47 ignition control module cause everything not to work? We had to replace the one in the downstairs unit a few years ago because the furnace wouldn't ignite. The LED on the 50E47 is dark and not blinking.

I have a multimeter and I can do some detective work, I just need some pointers on where and what to check and what the things to check look like. Please let me know if you need more information.

Thanks,
Kurt

 

make sure the batteries are good in your stat. Sounds like you dont have 24V to the thermostat, so first need to check for 24V at the furnace and then for 24V to the stat and then 24V coming back from stat to G and Y

 

Thanks for replying. The batteries in the thermostat are fine. The thermostat is detachable from the wall plate with the wire terminals. I've swapped the upstairs and downstairs thermostats and both work downstairs but not upstairs.

At the thermostat I have the following wires hooked up:
C - blue
RC - red (also jumpered to RH)
W - white
Y - yellow
G - green

I opened up the bottom of the furnace (looks like the blower unit) and found the terminals the thermostat is hooked up to. There is also a sticker under the terminals with the following labels:
C - blue (Remote A/C)
W - white (Thermostat)
R - red (Thermostat)
Y - yellow (Remote A/C)
G - green (Thermostat) (24 Volts is also printed under the G)

Can you please expand on how to test for 24V at the different locations and do I test with the thermostat turned off? I'm new to this, but would like to learn the basics of how these work. Thanks.

 

at the control board, check for 24V AC between R&C with the door switch pushed in. Next turn a/c on at the thermostat. Then check for 24V between G & C and Y & C at the control board with the door switch pushed in.

 

Probably easiest to test at the thermostat location. You must have the blower compartment door in place because it closes a switch that when open shuts off all power to the furnace.

Set the multimeter to VOLTS AC and the range to 150 or less. Test between the C (blue) and R (red) wires to see if you get about 24 volts. If no, then do the same test at the furnace/air handler while also holding in the plunger switch. If still no voltage then you need to check for 120 volts coming into the furnace/air handler.

If this 120 volt power test shows power coming in then you need to look for a fuse in the transformer leads. There may not be a fuse, some have one and others do not. Post back with results of these tests.

 

Thanks for the instructions.

0 volts at the thermostat
0 volts at the blower
no power to the 120 volt socket
15 amp fuse in garage electrical panel not tripped

There is a round, threaded 10 amp fuse below the 120 volt plug on the wall that has blown. So I'm going to replace the fuse, but I will not be surprised if it blows again.

Given how old it is and how long it has been since it was serviced what kinds of things should I check before turning it back on? It's pretty dirty inside so I'm going to clean it out first. I know I need to get someone out to service both units but I don't know when I'll be able to do that (hopefully in the next few months). Thanks for your help.

 

blower motor is the only thing that really draws anything close to 10 amps in the furnace. Check the capacitor if there is one...for the blower motor. You can also try turning the blower cage by hand with all power off to the unit..... it may be seized

 

I vacuumed out the blower unit (wasn't very dirty). There was a loose 1" piece of filter material on the side of the blower sort of covering the return air duct that is attached to the side of the blower. I pulled out the filter (very dirty) and will look for something this weekend to replace it.

The blower turned freely when I moved it. The blower has a sticker on it indicating it should be removed, cleaned, and the motor oiled every three years I'll have to pull it out soon and do that. It says #10 motor oil. Is that car motor oil or a different kind of oil?

I replaced the 10amp fuse and tested the voltages and got 26.2 volts across C and R at the blower. The transformer makes a noticeable hum when powered.

I turned on the AC and it is working again. I'm still not sure of the cause so I'll have to keep an eye on it. Thanks for all the help!

 

As luck would have it my downstairs unit stopped working today.

Snyder General Comfort Maker: GDE067A012AIM (mfg 09-1989)

Same problem, blown fuse. This one has a Buss Type S 12 amp plug fuse. Home Depot of course only has 10 and 15 amp fuses. The blower on this unit is 1200 CFM like the other unit. Is there any reason I can't use a 10 amp fuse with it until I can find a 12 amp fuse?

I can get the 12 amp fuse online, but would like to try and find one locally if possible. The large chain stores only carry them in multiples of 5 amp. What kind of company should I be looking for that would sell these locally? I've been looking through the phone book and mostly see commercial resellers and the like. I'm in the East Bay Area, CA if that matters.

Thanks

 

should look for an electrical store. The 10A could be used temporarily but the 15 is too much.