jM20 Posted February 8 Report Posted February 8 Hi! I'm not sure if im missing remembering or not. We took the float out to do a tank repair. After putting the float back in, the reading on the gauge was past the top. There is only one wire going to the sender. I thought the problem was a bad ground, so I attached a wire to the post and the other end to a screw. I managed to short the gauge now so that it only reads 0. I looked in the manual and its of no help how this goes back together. I'm pretty sure I looked at the other side and it looks like I put it together correctly. Any ideas? Thanks in advance!! Quote
DCarlton Posted February 8 Report Posted February 8 I'm not a mechanic but I'm dealing with similar issues. I think the C may have one sender per tank. My F has two per tank in series. I think they are all 0-30 ohms. You could move the sender through its operating range and check that between the post and ground. Your second pic is definitely not correct; you answered your own question about the short to ground. I'm guessing it's installed in the same orientation it was removed. Air Parts of Lockhaven overhauls those senders and gages. It's not cheap but cheaper than new. You'll get good guidance from someone here. I'm not an expert. 1 Quote
hammdo Posted February 9 Report Posted February 9 Only wire to the center post should be the hot wire. When airpark overhauled mine, they make it so you cannot remove it. I had to add a ground on mine to make sure it reads properly. A full reading is a no ground situation. in your pic, the gasket or screws are leaking so you’ll need to address that… BTW, Air Parts doesn’t send a gasket for the sender so you need to ask for one… -Don 1 Quote
DCarlton Posted February 9 Report Posted February 9 5 hours ago, hammdo said: Only wire to the center post should be the hot wire. When airpark overhauled mine, they make it so you cannot remove it. I had to add a ground on mine to make sure it reads properly. A full reading is a no ground situation. in your pic, the gasket or screws are leaking so you’ll need to address that… BTW, Air Parts doesn’t send a gasket for the sender so you need to ask for one… -Don The five screws weren’t enough for a good ground? How did you add a ground? From a screw to? Quote
hammdo Posted February 9 Report Posted February 9 No, screw wasn’t enough (it should have but wasn’t). I added one from one of the bolts to a common ground. It’s in the pics. -Don 1 Quote
jM20 Posted February 10 Author Report Posted February 10 On 2/8/2024 at 6:30 PM, DCarlton said: I'm not a mechanic but I'm dealing with similar issues. I think the C may have one sender per tank. My F has two per tank in series. I think they are all 0-30 ohms. You could move the sender through its operating range and check that between the post and ground. Your second pic is definitely not correct; you answered your own question about the short to ground. I'm guessing it's installed in the same orientation it was removed. Air Parts of Lockhaven overhauls those senders and gages. It's not cheap but cheaper than new. You'll get good guidance from someone here. I'm not an expert. I’m just not sure where the ground should make contact? It doesn’t seem to from the screw holes themselves. Quote
jM20 Posted February 10 Author Report Posted February 10 On 2/9/2024 at 1:02 AM, DCarlton said: The five screws weren’t enough for a good ground? How did you add a ground? From a screw to? I’m not sure, I don’t think so. What im really not sure about it where the ground contact point is on the sender. Quote
jM20 Posted February 10 Author Report Posted February 10 On 2/8/2024 at 7:17 PM, hammdo said: Only wire to the center post should be the hot wire. When airpark overhauled mine, they make it so you cannot remove it. I had to add a ground on mine to make sure it reads properly. A full reading is a no ground situation. in your pic, the gasket or screws are leaking so you’ll need to address that… BTW, Air Parts doesn’t send a gasket for the sender so you need to ask for one… -Don On 2/8/2024 at 7:17 PM, hammdo said: Only wire to the center post should be the hot wire. When airpark overhauled mine, they make it so you cannot remove it. I had to add a ground on mine to make sure it reads properly. A full reading is a no ground situation. in your pic, the gasket or screws are leaking so you’ll need to address that… BTW, Air Parts doesn’t send a gasket for the sender so you need to ask for one… -Don That was a mistake! Forgot to tighten the screws down again after screwing around with the probe and then went flying. It’s not straight forward what orientation the probe should be in either… Quote
jM20 Posted April 14 Author Report Posted April 14 Thanks all for the feedback!! I'm finally getting back to the issue since its in annual now.. I took the sender out and hooked only the center wire up, and then grounded the casing. The gauge reads 1/2 full when empty. When I lift the float to full, the gauge reads way past full. The gauge does go up and down with movement of the float up and down. The zero is just off! I tried to bend the stop a little, but it only seems to make things worse. Onto repair, next step try to see what the resistance is? Thank You!!! Quote
cliffy Posted April 14 Report Posted April 14 Its 30 ohm system Hook a 15 ohm (10%- gold stripe) resistor the center wire and the other end to ground and you should see 1/2 tank on the gage. The lever on the tank transmitter should go from near 0 ohms to about 30 ohms smoothly If it jumps around a lot during the travel its in need of work. Don't tighten the gasket screws down too tight or you will deform the mount hole and have a heck of a time trying to seal the transmitter even with a new gasket I always use a LITTLE aviation Titeseal gasket sealer on them when I assemble them. 1 Quote
Fly Boomer Posted April 14 Report Posted April 14 41 minutes ago, cliffy said: Its 30 ohm system Hook a 15 ohm (10%- gold stripe) resistor the center wire and the other end to ground and you should see 1/2 tank on the gage. The lever on the tank transmitter should go from near 0 ohms to about 30 ohms smoothly If it jumps around a lot during the travel its in need of work. Don't tighten the gasket screws down too tight or you will deform the mount hole and have a heck of a time trying to seal the transmitter even with a new gasket I always use a LITTLE aviation Titeseal gasket sealer on them when I assemble them. @jM20 says "The gauge reads 1/2 full when empty. When I lift the float to full, the gauge reads way past full." Is there supposed to be a resistor in the circuit? Quote
Pinecone Posted April 14 Report Posted April 14 No resistor. 0 ohms is empty. You have a bad connection that has a resistant of 15 ohms. Quote
Fly Boomer Posted April 15 Report Posted April 15 1 hour ago, Pinecone said: No resistor. 0 ohms is empty. You have a bad connection that has a resistant of 15 ohms. @Cliffy said a 15 ohm resistor is required to make the sender read correctly. Quote
Pinecone Posted April 15 Report Posted April 15 No, he said to test the gauge, hook up a 15 ohm resistor to ground is it should read 1/2 tank. 1 1 Quote
Fly Boomer Posted April 15 Report Posted April 15 1 hour ago, Pinecone said: No, he said to test the gauge, hook up a 15 ohm resistor to ground is it should read 1/2 tank. Thanks. I was trying to take something simple, and make it complicated. Quote
jamesm Posted April 16 Report Posted April 16 Keep in mind that various Mooney M20C model years especially in mid 60's had different size fuel tanks. Some fuel tanks were 52 gallon capacity, which has 26gal 156Lbs a side while other earlier years, I think some where 48 gallons 24 gallons /144lbs a side. I believe the tank sender resistance changed as well. my 67'C 52 gal 156Lbs a side indicated on fuel Gauge is a 30Ω. I am not sure but I think that the later year 'C' models like in the 70's may change the resistances for the fuel senders again. James '67C Quote
Pinecone Posted April 16 Report Posted April 16 AFAIK ALL Mooney fuel sensors are 30 ohms at the top of their stroke. Even on the ones with 2 senders per tank. With 2 senders, they are wired in series, so full on the gauge is 60 ohms resistance. Quote
cliffy Posted April 18 Report Posted April 18 The tank senders were originally out of a 50s Cadillac :-) Quote
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