AquaPure 1400 service codes 120 121


New member
Nov 1, 2010
I am running a 3 1/2 year old Aquapure 1400 and have been getting codes 120 & 121. Chlorine production seems to have decreased. Deposits build up quickly inside the cell, and despite frequent cleaning, the codes persist.

In an effort to figure out what is going on, I did the test procedures outlined in this file: ... Manual.pdf. Here's the results:

Front Board Firmware rev# 112305A
Back Board Rev. 8 B10032-08A

Back Board Transformer Voltages
test points 1-8 76.6 VAC (should be 75 VAC)
test points 2-7 66.6 VAC (should be 65 VAC)
test points 3-6 20.97 VAC (should be 21 VAC)
test points 4-5 51.5 mVDC (should be 120 mVDC)

Cell Voltage 35.5 VDC (should be 22 - 28) tested at Back Board test points
Cell Voltage 34.95 VDC tested at cell

Front Board Current Test (w/ cell on)
test points H-K 49.1 mVDC (should be 120 mVDC)
test points A-C 20.9 VAC (should be 21 VAC)

Salinity test button 2.8 GPL (should be 2. GPL)
R Temp test button 74 (should be 75)
H Temp test button 91 (should be 91)

Now that I have this information, I really don't know what it means.
Do I have a transformer problem? A board problem? A cell problem?

Any help with this would be greatly appreciated.


Well-known member
Oct 4, 2010
Test the salt concentration in the water. It should be between 3.0 and 3.5 g/l (3000-3500 ppm).

Ohm test the cable. Check the cord connections at the board and at the cell.

Inspect the cell.
A small amount of scale is normal. You can usually hose it out with your garden hose.
If rinsing with your garden hose does not clear the scale, it may be necessary to mild acid wash the cell. Clean with a 4 to 1 mild acid bath. 4 parts water to 1 part muriatic acid as per the manufacturers instructions.

Check the current on the front board. Usually around 120 DC millivolts.
Check the DC voltage on the back board at board and at the cell. Usually around 24 vdc.

If DC voltage exceeds 28 VDC (your reading is 35.5) or less than 120 DC millivolts (your result is 49.1), then
replace cell and cord. :-(

Properly balanced water is one of the best ways to extend the life you your salt cell.

Properly balanced water can slow the accumulation of scale on the cell and extend the time between cleaning and servicing ;-)
Invest in a good test kit like a Taylor 2006 or TF-100
Follow the recommendations found in pool school and enjoy your trouble free pool.


New member
Nov 1, 2010
Thanks for the replies thus far.

Currently my water balance is good, as tested at my local pool supply store. Salt is at 3400. Build up of deposits in the cell has always been a problem even with consistently balanced water. Water supply here is very hard, so that may be a contributing factor. I usually end up cleaning it monthly by soaking it for 20 minutes in a 4:1 dilution of muriatic acid.

Poolschoolgrad, based on your reading of my test results, you recommend replacing both the cell and dc cord. Not to doubt your recommendation, but do you have expertize with these components? I have a feeling that the cell may be going bad, but I would like to know for sure that this is the case before I shell out a ton of money on a replacement.

Melt In The Sun

TFP Expert
LifeTime Supporter
Oct 29, 2009
Tucson, AZ
kejacobsen said:
Currently my water balance is good, as tested at my local pool supply store.
Here's a problem. "Good" doesn't tell us very much, and most of the time a pool store's version of "good" is well...broader than ours.

Hard water (=high calcium) is one part of the puzzle, but even with very hard water you can manage to not have scale buildup to the extent that you describe. I don't want to overwhelm you with the details right now, but a combination of high CH, high TA, and high pH will greatly increase the rate of scaling in the cell. If you get a good test kit, you can accurately measure and manage these numbers (pool store tests are not accurate, based on thousands of reports on this site).

The TF-100 (link to TF Test Kits in my sig) is an excellent choice, as is the Taylor K-2006 (though this is quite a bit more expensive for the same tests).


New member
Nov 1, 2010
I have a Taylor test kit but was out of reagent to test CYA, so I did the most recent tests at my local Leslie's Pool store. They use a Taylor kit as well, so as long as their reagents aren't out of date, the results should be accurate. As best I can remember (I'm at work now) here's the results:

FC 5.0 (recently shocked)
PH 7.5
TA 120
CH 410
CYA 75

Also, Pool Store tested my salt level at 3.4 while my Aquapure reads out 2.9 - not sure which is right.


Well-known member
Oct 4, 2010

My advice is based on the information provided by the manufacturer and experience with DC circuits. The results you provided are common with cell failure.

I would like to know for sure that this is the case before I shell out a ton of money on a replacement.
This is completely understandable. The replacement cells are expensive.

Jandy customer service number is 707.776.8200

There is always a certain level of risk involved when taking free advice from strangers over the internet. If you are uncomfortable, another option would be to hire your friendly neighborhood pool tech. Then it will be his responsibility to provide the correct replacement part(s). He will charge you the normal hourly labor rate and likely full retail for the cell and cord :mrgreen:

Please keep the forum informed of your progress.


New member
Jun 1, 2011
I noticed that this is an old post, but wanted to add my 2 cents.

SHORT version on the backboard is a Relay that reverses polarity to activate the self cleaning of the cell, look at the contacts if they show any discoloration yo umight have a bad relay and replacing it might be a way forward...


I was running into the same issues
Time line
- Sept 2010 replaced Sensor due to error codes and WEB findings
==> it worked, but I still got periodical error code 120 and 121
==> cell did produce chlorine, but at reduced rate and increased build up problem
==> March 2011 decided to buy new cell as problems persisted
- March 2011 replaced Cell, Sensor and Power cord
- found troubleshooting guide online, very helpful
==> error code 120/121 came back and cell deposit was quickly up
- with trouble shooting guide I determined that my cell turned on, but after short while turned off again
- I verified all voltages at test points, but the cell voltage went to 0 after 10-20 minutes
- called Jandy,what a waste of time, cell minutes and air
- first technician said, oh you have the trouble shooting guide? then you have to talk to advanced technician give me number and he will call you back
- Technician calls "Pierre"? After 15 minutes of back and force he wants to put me on hold and leaves me there for 30minutes and then the line went dead...
- He has my number, but never called back... OK this much about the great "service"
==> Logic applied
- cell starts
- cell turns off Error code and service LED "yellow" is on
==> my conclusion the reverse polarity is broken
- And here what you all have been waiting for
------- On the back board is a industrial 24V Relay, that reverses polarity, when I looked at the contacts under a microscope I was able to see that the contacts where burned up. Measuring the resistance of the contacts gave me 0.5ohm for the good one and ~39Ohm for the bad one.
==> bought a new relay at Mouser (great company 1 day shipping with ground/ I know their warehouse is only 10 miles form my house)
- replaced the relay
- cleaned the cell and voila we are back in business