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popsinflorida · Jan 30, 2007, 05:21 PM

We have a central ac/heat system by amana(modBMA42F10A).. ac works great..
Heat blows cold air... used last year and worked fine.. seems like heat coils are not turning on... I took them out cleaned and checked them for continuity.. put them back..
Temp limit sensor was dirty... (cleaned it with DG electronic parts cleaner) and heat still won't turn on. Ducts are in a1 shape.. could it be heat sensor, there are 2 of them (kind of hard to think both went bad) how do I check.. or any other ideas or advice would be appreciated...
Cold in fl for the 1st time.

Mike:confused:

NorthernHeat · Jan 30, 2007, 06:26 PM

This is an electric furnace? Do you have 24 volts between W (thermostat terminal) in the furnace and common?

popsinflorida · Jan 30, 2007, 07:41 PM

Yes the ac and the heat are both electric. (not a heat pump)i have some knowledge and tools... (contrary to what my wife thinks of me)lol
, but I am a little lost with electronics... thus I'm here... thanks 4 your reply northern heat...
I checked the voltage on the W (thermostat terminal) in the furnace and common...
Although its marked w2 and w3 which are piggy backed with one wire.
It read as 27.6 on a beckman (with thermostat set with heat on)... is it supposed to be set on acv. Thanks you again 4 your help

NorthernHeat · Jan 30, 2007, 08:14 PM

Yes A/C volts should be around 24 V. This tells me the thermostat is working. I don't know what you mean by heat sensor? At this point all you can do is, turn off the power, do a visual inspection of all the parts (something broken like a contactor might be obvious) look at the schematics and start Ohm'ing out the components. Or call a service tech.

popsinflorida · Jan 30, 2007, 08:34 PM

I'm sorry I meant heat relay... there are 2 and I do believe they run parallel..

And do you think the temp limitor could be compromised (would that prevent the heatcoil from turning on)it did have some type of corrosion on it, probably from condensation heat and dust . Thanks again

NorthernHeat · Jan 30, 2007, 09:11 PM

The temp limiter you speak off is either a fusable link, or thermal limit. Either one should Ohm near zero ohms if it is good. Be sure power is off, and at least one wire is disconnected from the device to check ohms.

popsinflorida · Jan 31, 2007, 06:25 AM

fuable links x2 , and temp limitor check in at 1 ohm each... is there a way to check the heat relays (HR1 HR2)... THANKS AGAIN :o

NorthernHeat · Jan 31, 2007, 04:16 PM

I need top know if they are relays or sequencers to tell you how to test them. In short, there is a low voltage coil that should test near 0 ohms. Or when you turn the power on you should hear them click, if they are not clicking I'll guess there is another safety limit in series with them, that might be the problem.

popsinflorida · Jan 31, 2007, 04:57 PM

They definitely are labeled as relays (temp limitor hooks into them)and they run directly to the coils, also a brown and grey runs from the board to the relays :confused:

NorthernHeat · Jan 31, 2007, 05:05 PM

I'm looking for a control, in series, of the low voltage power, to the relays.

popsinflorida · Jan 31, 2007, 06:02 PM

Found it , OK its white plastic square on board is labeled control (connects to both heat relays and temp limitor )... what should I do now ? :o

Control clicks when turned on and off but no heat... where do I check ohms on this... thanks... thanks and thanks again

NorthernHeat · Jan 31, 2007, 07:56 PM

Sorry I'm not sure what you are looking at, can you try and figure it out by looking at the schematic diagram? How many wires go into that component and what is normally open or closed contacts

popsinflorida · Jan 31, 2007, 08:27 PM

The schematic says it's the control it has brown and grey wires running into the heat relays.
It also has a yellow and orange wires leading to the temp limitor... it also has high voltage running in and out of it... I think I'm going to replace the temp limitor since it was the only thing that looked compromised... how much do they cost usually and where can I get one..
Please keep the trouble shooting ideas coming, I'm checking it out every time you post
Thanks a lot...

NorthernHeat · Feb 1, 2007, 02:45 PM

Look up Heating and air wholesalers in your yellow book for a supplier of parts. Most won't sell to the public though. I'm thinking the part with all the wire might be the problem. Some HVAC companies sell parts from there store front, we do.