carb heat box
Moderators: GAHorn, Karl Towle, Bruce Fenstermacher
- canderson
- Posts: 35
- Joined: Thu Oct 19, 2006 10:32 pm
carb heat box
Hi,
For a couple of flights now my carb heat gets stuck in the off position and may or may not work after some "fiddling." I took the cowling off and find that the bearing on the side opposite the cable connection seems to be off-center and binding. The cable and attachment are all newer and work just fine.
I see various kits for fixing this apparent problem and I also saw a what appeared to be a complete carb heat box for around $700. Anybody have experience with this problem and attempts to fix it?
Looks like it might be a poor design in the first place.
Thanks for the help
For a couple of flights now my carb heat gets stuck in the off position and may or may not work after some "fiddling." I took the cowling off and find that the bearing on the side opposite the cable connection seems to be off-center and binding. The cable and attachment are all newer and work just fine.
I see various kits for fixing this apparent problem and I also saw a what appeared to be a complete carb heat box for around $700. Anybody have experience with this problem and attempts to fix it?
Looks like it might be a poor design in the first place.
Thanks for the help
Chris
1953 170B N3234A #25878
1953 170B N3234A #25878
- GAHorn
- Posts: 21295
- Joined: Fri Apr 12, 2002 8:45 pm
Re: carb heat box
Regardless of the design, it is the one approved for the airplane and no substitute exists that I know of. Your best solution is to repair the box, which will probably require new bushings.canderson wrote:...Looks like it might be a poor design in the first place. Thanks for the help
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons.
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons.

-
- Posts: 395
- Joined: Wed Apr 23, 2003 10:48 pm
best route is the repair kit made by avglas which comes with a stc, can be bought from Mc farlane. I installed one on mine a few years ago. See
http://www.mcfarlane-aviation.com/Produ ... ber=FG-105&
http://www.mcfarlane-aviation.com/Produ ... ber=FG-105&
Vic
N2609V
48 Ragwing
A Lanber 2097 12 gauge O/U Sporting
A happy go lucky Ruger Red label 20 ga
12N Aeroflex
Andover NJ
http://www.sandhillaviation.com

" Air is free untill you have to move it" BB.
N2609V
48 Ragwing
A Lanber 2097 12 gauge O/U Sporting
A happy go lucky Ruger Red label 20 ga
12N Aeroflex
Andover NJ
http://www.sandhillaviation.com

" Air is free untill you have to move it" BB.
- 170C
- Posts: 3182
- Joined: Tue May 06, 2003 11:59 am
Carb Air Box Repair
I just went through this last month on my annual. In my case we suspected we would need to put in new bushings. Turned out that the problem was actually the shaft itself. One side was worn 1/2 way through and the other one was about 1/3 worn through. My IA replaced my shaft with a stainless steel one w/ threads on either end. Biggest job was cutting old shaft & getting flapper/butterfly loose from old shaft. Welded butterfly to new shaft. Works fine.
OLE POKEY
170C
Director:
2012-2018
170C
Director:
2012-2018
-
- Posts: 3485
- Joined: Sat May 06, 2006 6:05 pm
Chris-
If you don't want to do the job yourself, send it to F. Atlee Dodge, 877-332-8533, http://www.fadodge.com. They do lots of them and it will be a good repair. Not cheap but good work. They have done three for me over the years on different planes. Talk to Steve.
If you don't want to do the job yourself, send it to F. Atlee Dodge, 877-332-8533, http://www.fadodge.com. They do lots of them and it will be a good repair. Not cheap but good work. They have done three for me over the years on different planes. Talk to Steve.
Richard Pulley
2014-2016 TIC170A Past President
1951 170A, N1715D, s/n 20158, O-300D
2023 Best Original 170A at Sault Ste. Marie
Owned from 1973 to 1984.
Bought again in 2006 after 22 years.
It's not for sale!
2014-2016 TIC170A Past President
1951 170A, N1715D, s/n 20158, O-300D
2023 Best Original 170A at Sault Ste. Marie
Owned from 1973 to 1984.
Bought again in 2006 after 22 years.
It's not for sale!
-
- Posts: 395
- Joined: Wed Apr 23, 2003 10:48 pm
The kit supplied by Avglass can be installed by any A&P that can work a flame stick. I did mine a few annuals ago, when I recieved the kit it took me about two hours once I had the airbox off.
Vic
N2609V
48 Ragwing
A Lanber 2097 12 gauge O/U Sporting
A happy go lucky Ruger Red label 20 ga
12N Aeroflex
Andover NJ
http://www.sandhillaviation.com

" Air is free untill you have to move it" BB.
N2609V
48 Ragwing
A Lanber 2097 12 gauge O/U Sporting
A happy go lucky Ruger Red label 20 ga
12N Aeroflex
Andover NJ
http://www.sandhillaviation.com

" Air is free untill you have to move it" BB.
- canderson
- Posts: 35
- Joined: Thu Oct 19, 2006 10:32 pm
OK,
Thanks for all the replies. Here's a novice question.
Can I, being the mere owner, remove this carb heat box, without an A&P present, and send it to an approved repair facility and then replace it myself once it's fixed?
I know about the owner allowed preventive maintenance, but not having studied the other maintenance FARs, I'm not sure about some of these "what ifs."
Thanks again
Thanks for all the replies. Here's a novice question.
Can I, being the mere owner, remove this carb heat box, without an A&P present, and send it to an approved repair facility and then replace it myself once it's fixed?
I know about the owner allowed preventive maintenance, but not having studied the other maintenance FARs, I'm not sure about some of these "what ifs."

Thanks again
Chris
1953 170B N3234A #25878
1953 170B N3234A #25878
- jrenwick
- Posts: 2045
- Joined: Thu Apr 01, 2004 8:34 pm
Yes, you can do all that work, but before the airplane can be flown again, there must be a log entry describing what was done. That entry must be signed by a licensed A&P mechanic. So first figure out who's going to sign your log, then work it out with them how the work is going to get done.
The mechanic will probably at least want to inspect the result before signing the log, and he might only be willing to sign it if he does the work himself. Or something in-between, where you do the work under his watchful eye -- it's all up to the mechanic whose license is on the line.
Best Regards,
John
The mechanic will probably at least want to inspect the result before signing the log, and he might only be willing to sign it if he does the work himself. Or something in-between, where you do the work under his watchful eye -- it's all up to the mechanic whose license is on the line.
Best Regards,
John
John Renwick
Minneapolis, MN
Former owner, '55 C-170B, N4401B
'42 J-3 Cub, N62088
'50 Swift GC-1B, N2431B, Oshkosh 2009 Outstanding Swift Award, 2016 Best Continuously Maintained Swift
Minneapolis, MN
Former owner, '55 C-170B, N4401B
'42 J-3 Cub, N62088
'50 Swift GC-1B, N2431B, Oshkosh 2009 Outstanding Swift Award, 2016 Best Continuously Maintained Swift
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- Posts: 369
- Joined: Sat Jan 21, 2006 6:27 am
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- Posts: 507
- Joined: Sat Oct 18, 2003 9:07 pm
Yes... However to legally fly it again the work would have to supervised and signed off by an A&P.canderson wrote:OK,
Can I, being the mere owner, remove this carb heat box, without an A&P present, and send it to an approved repair facility and then replace it myself once it's fixed?
John
N2865C
"The only stupid question is one that wasn't asked"
N2865C
"The only stupid question is one that wasn't asked"
- GAHorn
- Posts: 21295
- Joined: Fri Apr 12, 2002 8:45 pm
Well...yes....and ....no. You can remove it. You can re-install it. It may not be legally flown until inspected and determined to be airworthy.
Can an ordinary A&P inspect it for airworthiness for return to service? No. An A&P may supervise your work, and then he may approve it for return to service.
But you may not perform work out of view of an A&P and then it be completely legal for him to sign off your work. This is because the rule requires that an uncertificated workman must be under the DIRECT supervision of the A&P. He must be there and witness the work as it is being performed. This does not mean the A&P can come along later after the work was performed and say "it looks alright to me" and then sign it off as if he supervised the work.
To approve the return to service of an airplane that has not met the rule it must be inspected by an A&P with Inspection Authority.... (an "IA")...before it is returned to service. (This is my opinion based upon lots of research-reading and official-opinion-solicitation from the FAA. It is not the convenient answer, but I believe it is the correct one.)
Can an ordinary A&P inspect it for airworthiness for return to service? No. An A&P may supervise your work, and then he may approve it for return to service.
But you may not perform work out of view of an A&P and then it be completely legal for him to sign off your work. This is because the rule requires that an uncertificated workman must be under the DIRECT supervision of the A&P. He must be there and witness the work as it is being performed. This does not mean the A&P can come along later after the work was performed and say "it looks alright to me" and then sign it off as if he supervised the work.
To approve the return to service of an airplane that has not met the rule it must be inspected by an A&P with Inspection Authority.... (an "IA")...before it is returned to service. (This is my opinion based upon lots of research-reading and official-opinion-solicitation from the FAA. It is not the convenient answer, but I believe it is the correct one.)
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons.
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons.

- ak2711c
- Posts: 283
- Joined: Tue Apr 23, 2002 6:29 am
I believe the amount of supervision is on a case by case basis. The A&P needs to inspect each stage of the project if it can not be adequately inspected all at once when it is done. Also how much supervision has a little to do with the ability of the person doing the work. It is up to the mechanic to determine at what stages he wants to inspect it. After all he is the one putting his name on the line for it. That has how our local FSDO interprets it. We can take any FAA reg out there and do the most conservative strictest interpretation of it and make our lives more difficult if we want but its not necessary.
Shawn
Shawn
Cessna® is a registered trademark of Textron Aviation, Inc. The International Cessna® 170 Association is an independent owners/operators association dedicated to C170 aircraft and early O-300-powered C172s. We are not affiliated with Cessna® or Textron Aviation, Inc. in any way.