Johnson Control A419 Problem

Hi,

I searched the forums but could not find anything about the issue I am having with my A419 controller. It works perfectly for weeks or even months straight but every once in a while it will show that the fridge is over 100*F (today it was showing it at 117). I checked the temperature with another (handheld) thermometer and it showed it at 25*F. I have the unit set to 65 with +/- 5 *F setpoints.

Has anybody experienced this problem with one before, or have any suggestions as to what might be wrong?

Thanks.

Hello I work in HVAC and I use A419's on equipment regularly the unit itself is very sturdy and reliable with a simple SPDT switch in it. However the temperature probe can be fragile. They use pretty good materials to protect the wiring inside but they can still fail. I have seen them do the exact thing you are talking about before and you can order a replacement probe for the unit.

The replacement probe is called a johnson controls a99b. I think the come in two different lengths and cost around $25 also make sure the probe hasnt been getting wet inside the fridge the company states they are "splash proof" and not water proof. A lot of times I will put a small plastic bag over the sensor and zip tie it behind the probe on the wire for added protection just make sure the bag it tight or condensation could build up in it.

OP I am currently going though the same issue, what a pain!

Does is indicate an odd "CO3" error, or mod thing similar, only to go away shortly thereafter?

Roboto - thank you! I keep my probe in a glass of water, I probably damaged it. I'll get a replacement probe.

Also roboto, any experience with control products tc 9102 single stage?

Ugh $36 w shipping, damn.

are the probes waterproof? everything I have read says the probes are not. Use a thermowell if immersing in liquid.

Wow, I'm glad I read this. I have an A419 on order that will come in a few days. I was planning on using it to temp control my HLT and eventually for a HERMS build. Didn't realize the temp sensor wasn't waterproof. What sort of thermowell are people using for an HLT? The same as used in carboys or homemade?