Coleman furnace blower will not come on

[jlraymond]

I have a Coleman furnace model 3500-816, Serial Number 088878254 (54,000 btu’s).

1. We had a heating element not functioning, so we ordered and installed both heating element units (total of three elements).
2. We also had the blower motor cleaned as it was running out of balance, but after cleaning, seemed to be running smooth and true. Everything seemed to be working correctly for about three weeks, then the blower motor fails to come on.
3. We had the blower motor removed and attached to a 120 volt power supply and the motor works for both low and high speeds. We reattached the motor and have been trying to figure out why the motor is not coming on?
4. We then suspected the sequencer might be not functioning correctly, so we replaced it as well and still the motor does not come on.
5. The only part we have not replaced is the transformer. It does seem to be getting 240volts but not sure what outputs we should get from the other leads.

The symptoms are that you turn up the controller above the current room temperature. You can hear a click from the furnace and can see the heating elements energize, then after about 7-8 seconds another click from the furnace and can see the elements turn off. I believe that once the heating elements come on and without the fan coming on, the set temperature is reached and then shuts the elements off. If the fan were to come on, I’m thinking that the furnace would be staying on longer.

What have we missed and why is the blower fan not coming on???

Thanks so much for your help. If the transformer or other part is believed to be at fault, please let me know so I can order them.

[Robert]

Hi,

Set the t-stat to heat-auto-85* for a call for heat. Then when blower does not run, carefully use something to give the wheel a spin.

See if it starts and runs then. If so, probably a bad run capacitor. Motor could be bad or going bad as well.


If it does not run, then may be a loose wire connection in the blower molex plug or in a wire nut.


Thanks,
Robert

[jlraymond]

Thanks for posting a reply. Any help is much appreciated. I have tried spinning the blower motor which turns freely. When troubleshooting, I did give the blower an independant power supply to 120v and both the low and high side did work and the motor seems to run quiet and smooth. If the blower runs this way, would the capacitor be faulty? And if so, where is the capacitor physically located?

Thanks!
Jim

[Robert]

Hi Jim,

The run cap is usually attached to side of blower housing. At 120vac, motor would run slower than with the 240vac it is designed for.

Power it up normally and spin the wheel to see if motor kicks in and runs.

Also test and see if you have 240vac across the two motor leads for speed you're needing.


Thanks,
Robert

[jlraymond]

Robert,
First off, thanks for your patience and your advice. From your last posting, I checked both the blower motor capacitor and also the connector where the wires come together. The issure remains, but did do some testing with my electrical tester to try and determine why I'm not getting 240V to the blower.

One question I do have in regards to this coleman furnace: When operating correctly, should the fan always be on and the heating elements cycling on and off to regulate the temperature throughout the house?

When following the wiring from the motor, I ended up back to the squencer that I had just replaced. I hope this makes sense: The sequencer has two controlers (one short and one tall). Connected to the taller one a blue wire (this blue wire routed back the the MOLEX plug is the red wire to the blower motor).

The old sequencer taller controller had the blue wire connected to a connector called M2. At the M2 end of this controller there are two wire termals where as the top of the controller only has one wire termal which is labeled M1. I just noticed that the new sequencer has two wire terminals at both the M1 and M2. If I connect this blue wire to the M2 (which is how it was originally with the old sequencer), the fan never gets 240V and never comes on. The heating elements click on for about 5 seconds then shuts off. If I simply move the blue wire to the M1, the fan continually runs and the heating elements do cycle on and off which does seem to regulate the temperature.

If the fan is supposed to be on all the time for this furnace, then I would think that this wire configuration is correct. But if the fan is supposed to cycle off, then it seem that perhaps the sequencer is not working correctly. What is your opinion and suggestion?

If the sequencer is faulty, I might need to order another one. I thought that perhaps I had ordered the wrong sequencer but the number do seem to match even though there is the slight wire terminal addition to the replacement.

Please help?
JIm

[Robert]

Hi Jim,

There should be another wire connected at M2 beside the blower wire that goes over to a terminal on a white ceramic insulator at far left end of one of the element coils.

Locate that element terminal, set t-stat to call for heat, place blue wire back on M2 and then test at the element terminal to a metal ground for 120vac.


Let me know what you got.

When did you install that sequencer ?

Leave blue wire on M2.


Thanks,
Robert

[jlraymond]

Hi Robert,

Thanks again for your reply back and your patience with me and this problem.

There is another wire connected at M2 (a yellow wire) just as you described.

I will test the element terminal for 120vac and let you know what we have.

The furnace was having issues and the local repair company wanted to replace the entire unit, but what they wanted to very expensive. The repair company said that the 1/2 elements were faulty, the sequencer and blower were also in need of replacement and that replacing the entire furnace was more cost effective. My folks paid the repair company for their visit (~$430) which didn't fix anything and then they wanted me to figure it out. I found your website and ordered both heating assemblies for all three elements with new controllers, and a new sequencer.....probably about 5 weeks ago. The blower was cleaned out with compressed air and blades wiped which made it run quiet and seemed to be in balance. The unit ran fine for about 2 weeks then the blower stopped coming on.

That's what brought us to where we are at now.

Again, I appreciate your help in figuring this out. When I moved the blue wire from M2 to M1, at least I was able to keep the blower running and the furnace is keeping the house at perfect regulated temperature........but my thought is that the blower should also be cycling on and off. So they are better then just the heating elements coming on with no blower.

Will let you know about the vac reading......thanks!

Jim

[Robert]

Hi Jim,

IF the heat is still needed, leave the blue wire on M1 OR place it on M2 and set t-stat fan switch to ON-Cont. .


IF t-stat does not have a fan switch, set the furnace switch to Fan ON / Cont. .

That will keep the blower on at all times also.

You can also test from the M2 terminals (remove the blue and yellow wires) to a metal ground for 120vac.


Same as testing at element terminal.

Do not run furnace without the blower.



Thanks,
Robert

[jlraymond]

Hi Robert,

My problem with this furnace continues but do have some additonal information for you to consider. The current situation is with a coleman furnace. The fan blower was not coming on when the heating elements came on. The elements would be on for several seconds, then cycle off. This would repeat after several minutes (I assume that the elements would cycle on when the system determined that more heat was needed).

I had moved a blue wire from the M2 terminal to the M1 terminal which keeps the blower fan motor running constantly (the M1 terminal gives the blower 240VAC). The system is maintaining the house temperature that is set at the tstat.

As you requested, I tested the M1 and M2 terminals to ground and all gave a reading of 120VAC.

So at this point, what we do know is that:
1. The blower fan does work when the blue wire is moved from M2 to M1 giving it 240 VAC.
2. The heating elements seem to cycle on and off correctly.
3. The M1/M2 terminals to ground have 120VAC.
4. The blower fan will work when given 120 or 240VAC from an independant power source.

What we don't know is:
Why the blower fan won't come on when the heating elements cycle on when the blue wire is on M2. Could it be that given that the M2 terminal with 120VAC to ground is not giving the blower fan 240VAC?

The only parts replaced have been the heating elements and the sequencer. The sequencer we decided to replace when it seemed the logical part to resolve the fan not coming on with the elements. The current situation does not change when the original sequencer is reinstalled.

Again, I apprecate your incite and help in resolving the problem. If it is a part that needs replacing, please let me know so I can order it.

Very best regards,
Jim

[Robert]

Hi Jim,

Look on the blower housing for the blower assembly part number.

Also give me the Coleman p/n off of the blower motor.




Thanks,
Robert

[jlraymond]

Hi Robert,
Here is what I have for numbers.

Blower housing assembly:0106-881
Blower motor: 3500-590
S/N for furnace: 088878254

Hope this helps. Please let me know what is going on and what I need to do or replace to resolve the blower not coming on with the heating elements. Right now, I have the blower still wired to be on all the time and the furnace is correctly regulating the temperature.

Thanks!
Jim

[Robert]

Hi Jim,

With what you've told me here, it should be working correctly. So not sure what to tell you without being there.

The motor is a 240vac motor and has to have 240volts to run correctly.

It gets 120vac through the orange wire and the other 120vac through the blue wire from sequencer.

How it is wired now shows that the orange wire to motor is ok and the blue wire to motor is ok.

Having the blue on M1 gives that leg 120vac at all times.

When you move the blue to M2, the M1 to M2 contacts have to close on a call for heat from t-stat in order for the 120vac to get through to run the motor.

You stated that with a call from t-stat, that you have 120vac to ground from M2, so it is closing and sending the 120vac.

Therefore it should be running, but it isn't and without being there, I'm not sure what it is that is missing or wrong here.


IF you are getting the 120vac to ground from M2, then moving the blue wire from M1 to M2 would be the same because it is only getting 120vac from M1 also.


May be time to have an hvac tech see what is missing here.


Thanks,
Robert

[jlraymond]

Hi Robert,
Thanks for the reply back and wish it were better news. The funny thing with this unit is that the only thing wrong originally was that one of the heating elements was tested faulty. It was cost effective to simply replace all three elements and with a good cleaning out of the blower fan, the unit ran great for about two/three weeks. That's when it started having this new issue. You would hear a click from the furnace which was the elements coming on, the no fan. It seemed to me at the time that the one component that had not been replaced was the sequencer which from my understanding, turns the fan and heating elements at the same time/as needed. So we went and replaced that.

From what I gather, you are saying that the readings I sent you are correct? You don't suppose that the sequencer could be at fault? The odd thing is that p/n of the old sequencer does match the new one, but there are a couple of differences. The old sequencer has two wire connections for M2 and only one connection for M1......the new one has two wire connections at both M2 and M1.

Even with correct readings, could there be a possibility that the sequencer could be at fault?

Thanks again,
Jim

[Robert]

Hi Jim,

With the blue wire on M1, it is getting 120vac straight from breaker and since motor is working, that tells us the circuit through the blue wire is ok.

The blue wire circuit works IF it gets the 120vac.

When you place it on M2, the sequencer contacts have to close in order for the blue wire to get the 120vac.

You state with a call for heat from t-stat, that you read 120vac at M2 to ground and the elements are heating, so the contacts must be closing giving the blue wire the same 120vac.

Maybe only some of the elements are energizing and sequencer contacts not closing.

Something isn't right with all that, but I have no way of knowing what without being there.

Try this: Remove wires from M1 and M2 ONLY. Turn t-stat OFF.

Set meter to test for ohms and test across M1 and M2.

Then set t-stat to Heat-Auto-highest temp setting to get a call for heat.

Wait 30 seconds and test ohms across M1 and M2 again.

Tell me what it reads.


Thanks,
Robert

[jlraymond]

Hi Robert,
Again, thanks for writing and for your incite. I just got back from taking some reading and made an interesting discovery. The old sequencer and new sequencer have basically the same part number but the new sequencer is not labeled M1/M2, etc....it is labled H1/H2, etc. They both look physically the same. I was looking at the old sequencer is the P/N is 3115-357, where on the invoice of the new sequencer the P/N is 3115-3571. Not sure if this means anything but wanted to share what I discovered.

I was taking reading and still getting the 120VAC to ground on all the connections. When I was looking at the non-used wire connections on the new sequencer, I realized that there was an extra on the H3 position that is wired to the third heating element. I connected the blue blower fan wire to the H3, repowered up the unit and called for heat. The interesting thing is that now the heating elements come on with the blower fan and then the heating elements go off with the fan running a minute or so longer, then also cycles off. I have adjusted the Tstat and the system seems to be regulating correctly.

Could the sequencer to the wrong on for this unit? Or perhaps this sequencer is an improved part and just requires a different wiring configuration?

Thanks again for your incite!
Jim