124 electric fan - Page 11 - PeachParts Mercedes-Benz Forum

duxthe1 · #**151** 06-24-2022, 09:49 PM

I actually revisited my setup over the last week or so. I was noticing compressor cutout with cool engine but very hot ambient temps. Worked through my code and I found a bug in the bit of code that adds fan speed in high ambient temps. The > symbol was the wrong way around. I also realized that to get the high ambient temp bump there had to be some fan request, so I added a line of code to request 1st speed with the compressor engaged. With the hot ambient temp bump of 3 it has at least 1/2 speed (4 of 8) with the compressor on regardless of the ambient /refrigerant delta. We've got a bit of cooler weather in the near term so it will be a few days before I actually get to stress test it.

The other thing I'm thinking on, is adding an afterun for when the compressor switches off. Something like 10 seconds or so. It may take a fair bit of coding to get one dialed in and I'm not keen on a major revamp of the code but it would be a nice feature and I still have plenty of memory left on the board.

Roncallo · #**152** 06-26-2022, 06:32 PM

Quote:

Originally Posted by duxthe1

I actually revisited my setup over the last week or so. I was noticing compressor cutout with cool engine but very hot ambient temps. Worked through my code and I found a bug in the bit of code that adds fan speed in high ambient temps. The > symbol was the wrong way around. I also realized that to get the high ambient temp bump there had to be some fan request, so I added a line of code to request 1st speed with the compressor engaged. With the hot ambient temp bump of 3 it has at least 1/2 speed (4 of 8) with the compressor on regardless of the ambient /refrigerant delta. We've got a bit of cooler weather in the near term so it will be a few days before I actually get to stress test it.

The other thing I'm thinking on, is adding an afterun for when the compressor switches off. Something like 10 seconds or so. It may take a fair bit of coding to get one dialed in and I'm not keen on a major revamp of the code but it would be a nice feature and I still have plenty of memory left on the board.

At the moment I don't have a high ambient bump. But after running in FL at ambient of 99° F with the fan speed running at 80%, I am considering bumping the fan speed 10 or 20 % based on condenser temp. But I want to keep the normal operation range capped at 90%. I will let it run at 100% if the coolant temp reaches 115°C. 115°C is the temp where Mercedes cuts off the compressor on the 560SL. I still have an aux fan on my car that is supposed to come on high speed at 105°C. When I was running in FL my gauge was reading about 112°C but my app was reading 104°C. Unfortunately I couldn't tell if the aux fan was on when I was doing 70MPH and the temp would cool as soon as I got off the highway. So the plan is to put some temporary lights in to tell me what the aux fan is doing.

As far as an after run circuit. I will be using a Buler BU-509TD time delay relay connected to the non-PWM circuit of the fan. That means it will run at 100% for after run, but I did find that it does cool down reasonable quickly. I looked into a bunch of other scenarios to do this with the Arduino and they would be very nice, in that you could run a separate program just for cool down but I didn't like the added complexity. Easiest way to do it would be to have the Arduino powered at all times and accept a small parasitic current drain or turn the Arduino on with a 505 timer chip. Both would require bringing circuit 30 power into the control system.

https://www.delcity.net/store/Time-Delay-Relays/p_804415.h_804416.r_IF1003?&mkwid=s&crid=456573819067&mp_kw=&mp_mt=&gclid=CjwKCAjwh-CVBhB8EiwAjFEPGQr7SNZgsIMIWq5OJVxDv9JgRHCkD7wffY1sKSV7OiEwg9p5Qr_tORoCUzsQAvD_BwE

duxthe1 · #**153** 06-28-2022, 07:59 PM

I wasn't very clear regarding the afterun I'd like to setup. Specifically I'd like a compressor off afterun and not a vehicle shutdown afterun. When the compressor shuts off there is still hot refrigerant in the condensor that I'd like to go ahead and cool off and condense. The current setup shuts the fan off when the compressor turns off. These fans have a bit of a response delay but I'd like another 10-15 seconds in that situation.

As far as a vehicle off afterun, I don't really have a need for it. Even when my coupe is really heat soaked I can start the car, the fan kicks on high, and I can watch the temp drop in a very short window. In terms of engine temp management I couldn't be happier with the setup.... refrigerant temp...ehh

Roncallo · #**154** 07-03-2022, 02:05 PM

Quote:

Originally Posted by duxthe1

I wasn't very clear regarding the afterun I'd like to setup. Specifically I'd like a compressor off afterun and not a vehicle shutdown afterun. When the compressor shuts off there is still hot refrigerant in the condensor that I'd like to go ahead and cool off and condense. The current setup shuts the fan off when the compressor turns off. These fans have a bit of a response delay but I'd like another 10-15 seconds in that situation.

As far as a vehicle off afterun, I don't really have a need for it. Even when my coupe is really heat soaked I can start the car, the fan kicks on high, and I can watch the temp drop in a very short window. In terms of engine temp management I couldn't be happier with the setup.... refrigerant temp...ehh

I get you. I'm running a separate temps sensor on the condenser high side line. As long as the condenser is hot the fan will run at any programed speed I want it to.

As far as after run when shutoff, I also have no issues starting the car or anything else except I did notice the hood liner started to deteriorate quite rapidly after installing AC. So I figured a 15 second after run would be appropriate for that. I also noticed that if I run the 1/4 mile, the first run of the day is always the fastest. Even after letting the car sit with the hood open for about 20 min. So maybe a 30 second after run for that might help.

I also have an under hood temperature sensor, which unfortunately got damaged when I went to unsolder connectors and replace them with more suitable ones. I was advised by a gentlemen on All about circuits that you could use underhood temp in place of water temp. I also downloaded a research paper on it and found that that may have some credibility. But for now when I get underhood temp working correctly I will monitor it before jumping in. The guy that uses it claims it is much more responsive than water temp. Might be true as the underhood temp will be a direct result of exhaust manifold heat which I would expect to react quite rapidly.

Roncallo · #**155** 07-29-2022, 09:02 PM

The App is coming along slowly but surely. I at least got it to connect and report test #'s.

Thanks to Mr. Chris Ward on the MIT Forums. It will still be a while now as I have two more truck loads of crap to move to CT.

https://community.appinventor.mit.edu/t/possibly-damaged-two-nano-33-bles-trying-to-connect-to-app/58178/135