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Boston01X5 08-05-2018 07:56 AM

AC Issue - Control Panel or Control Module?
Hey everyone,

I have an issue where my AC stopped working, the control panel totally shutoff, it turned on heat, and when I pulled key out of ignition blower was still running.

The first time it happened I disconnected the battery and that fixed the issue for a few days, now it's back. I yanked the fuse so the blower isn't constantly running.

From what I've read it could be the FSU (blower resistor), the climate control panel, or the climate control module. Some people have had all 3 fix this issue from what I have read.

The FSU is cheap enough I could start with that.

Would appreciate any advice about how to determine what the problem is.

Thanks very much,


andrewwynn 08-05-2018 09:41 AM

Blower on power off the go-to is FSU (Final stage unit) aka FSR. But that won't usually take out power to the panel.

I would check all fuses related then expect to change FSU

Boston01X5 08-05-2018 09:56 AM

Your correct it's called the FSU, was a typo.

I will check fuses and grab an FSU today and put it in if needed.

Also, not sure if this matters but I have a scanner that can read codes from the individual modules. On this car there is almost 20 I believe. After this problem happened it no longer lists the AC module because I tried to check for codes. Not sure if that might be a clue as to what is wrong.

Appreciate the help very much, thanks


Boston01X5 08-05-2018 10:43 AM

Got a price yesterday for the FSU and was super cheap, $30 at Advanced Auto they ordered it and it was supposed to be here this morning. Just went but to pick it up and it's $130.

What should I pay for an FSU? Online they range from $30 on eBay, to over a hundred. I don't want to spend that type of money if that's not the problem. Generally with electrical parts as soon as you plug them in you cannot return that is what guy said.

Any advice?

Qsilver7 08-05-2018 11:08 AM

Do a google search using the phrase "BMW e39 FSR FSU Bluebee". This is a much discussed topic and back a few years ago Bluebee had a huge thread that discussed the different brands of FSR (final stage resistors) or FSU (final stage units) and many comments were made as to they longevity of several brands and the best ones to get.

Accordingly, any prices listed from over 3-5 years ago will not be the same...but the quality of the brand name should be similar. The e39 and e53 uses the same FSR/FSU.

Boston01X5 08-05-2018 11:41 AM

Thanks very much Qsilver, it's been over 90 here with crazy humidity for the past few weeks with no end in sight so what a time for this problem to happen ;)

I will check out that post now appreciate the heads up.

Boston01X5 08-05-2018 05:19 PM

Hey guys I had the day off so I did some diagnosing.

Found a video online showing how to test the power to the control panel there are two connectors on back, pins 1 on both are the power. With key in ON position they are both getting 12 volts which is perfect.

Also checked the ground to the control panel and it's also perfect.

So this control panel is getting power and has a good ground and is totally dead doesn't turn on at all.

Is it safe to assume I need to replace it?



PS: link to the video, I found it helpful - for anyone who finds this thread in future https://youtu.be/6AUacShEkbk

Boston01X5 08-07-2018 07:51 PM

Hey guys just an update, and in need of some help.

Got a used heater control panel, plugged it in and it is all lit up and controls the blower perfectly :)

It corrected the issue of blowing heat, and the blower running without key in ignition etc.

However there is no AC now, the fan for the AC doesn't kick on or anything.

Any suggestions?



amancuso 08-07-2018 08:18 PM

Did you put all your fuses back in?

Boston01X5 08-07-2018 08:29 PM

Yes I put all the fuses back in after installing the panel.

When I first installed the panel it lit up but blower was not running, then I put back fuse (the big 50 amp) blower kicked on and speed was controlled by the buttons no problem.

So when I click auto it bumps the blower speed to max, but for some reason is not kicking on the AC.

Thanks for the reply :) appreciate it.

Any suggestions where to look next?

andrewwynn 08-07-2018 08:38 PM

The usual: check pressure, sensor, aux fan

Sent from my iPhone using Tapatalk Pro

Boston01X5 08-07-2018 08:57 PM

Ok I'm first time BMW owner so trying to learn lol, owned a few Mercedes before this last being ML320. Love the X5 compared to that honestly 😉

Will check pressure of refrigerant and power to aux fan if that's what you mean? Also how do I check the sensor I am going to look it up now. The AC was working perfectly until the panel went dead heat kicked on and blower was running without key in ignition etc that was only a couple days ago so just wanted to make sure I wasn't missing something.

I bought this car because liked how it looked and runs good, plenty of power and thought it would be similiar to a Mercedes to work on. Silly me 😂

Will check out what you mentioned thanks very much.

andrewwynn 08-07-2018 09:18 PM

I recommend getting a decent scanner like foxwell NT510 you can manually engage AC compressor and override buttons eg "hit the AC button" to determine if it's a simple switch problem. It's $60 to add different car brands up to five total I think. Need the 520 model to also do Mercedes.

Example of the power of the tool: I can monitor the temp of the evaporator, both heat exchangers and the status of the heater core valves real-time.

There is a low pressure sensor on the return line from EVAP to compressor, mine had a loose connection when I bought my X5 and it will prevent the AC from engaging but I think I could still hit the AC button and it lit up just nothing happened.

If you don't get the snowflake then there is as different problem possibly just the button itself.

Boston01X5 08-08-2018 12:18 PM

That Foxwell scanner sounds great, I am going to look into.

I bought a BM II from icarsoft for a little under $200 for this car when I purchased the vehicle because it was supposed to be able to read all modules and I knew I would need to do that. The scanner you are talking about sounds much better and hopefully in my price range.

As far as the buttons go, I wasn't sure so just went outside and checked. When I click the button with a snowflake on it, the green light turns on. Does that tell us anything?

Also with the new panel in, the rear blower is constantly running, I have no idea what that is about.

I don't have a service manual for this car, tried to find one online but no luck and AllData has no information for it.

I can check the AC pressure no problem, I am not sure how to check the sensor or where it is that you mentioned in first post (check pressure, sensor, aux fan). I can probably figure out how to test the aux fan and see if its getting power. Any suggestions as to where I can get a complete service manual? Trying to fix this without a service manual is tough because I am not familiar with BMW.

I will also check out the low pressure sensor on return line.

I love this X5, but it is definitely not making things easy to fix lol.

Thanks Andrew, really appreciate the help.


andrewwynn 08-08-2018 01:12 PM

I bought a full service manual for $20 on eBay. Great because I can search the 3500 pages.

The NT510 was about $220.

There is a speed and temp control in the back seat for the HVAC. I suspect it was on high speed you just didn't know until the front panel was replaced.

Snowflake on means AC requested. Are you saying the compressor didn't kick on when pressed or no cold air made?

The dial in the center of dash mixes outside air so make sure there are three blue dots.

Boston01X5 08-08-2018 01:36 PM

Hey Andrew,

That's funny you mention the eBay thing because I bought one for like $10 when I first got the car, is about 3500 pages but has no table of contents or index so is sort of useless unless I want to spend hours scrolling through PDFs. No way to search that I saw, just gave me 3500+ pages of PDFs.

Can you send me a link to one that is similiar to yours? It did not have wiring diagrams but I was able to find a website for the wiring diagrams.

I just went outside and checked the rear heat/AC panel, it has one dial for temp on right of vents, and one with a little propeller on top and a 0 on bottom, I figured that was speed control but when I turned it to 0 blower still running - there are no buttons below it.

Yes when the snowflake is on, there is no cold air coming out of vents just air from outside, and the aux fan/compressor not kicking on. I have the dial set to the three little blue dots on center front dash. AC worked perfectly before had problem with panel dieing. Ice cold etc.

When I was trying to get a new main heater control panel what I replaced in front, they asked if my car had rear AC. I was not sure so I called local BMW dealer gave them the last 7 of VIN and they said it has rear AC but it does not have any controls back there besides two wheels.

When I went outside and started the car to check controls for rear seats, blower still running to back even if I shutoff the control panel in front totally.

$220 is very reasonable for a scanner that does all that. I will get one ASAP.

Here in Boston it's been almost 100 with humidity feels like 110 so this is the worst time for this problem to happen driving with windows down in traffic it's crazy hot lol my car is a dark blue so that doesn't help either.

Really appreciate the help bro,


andrewwynn 08-08-2018 10:31 PM

AC Issue - Control Panel or Control Module?
I researched months before pulling trigger on the nt510. It's pokey to get initialized but it does lots. I even bumped my idle speed 50 the other day.

Back fan speed is unrelated to front. If the fan speed dial won't slow the speed something is wrong


One giant PDF. Searchable. Can be tricky to find what you are looking for but it's pretty complete. Includes wiring diagrams. 625 MB file.

andrewwynn 08-08-2018 11:03 PM

Nt510 can directly engage the AC compressor. It will also scan virtually every module and find and reset errors.

Boston01X5 08-09-2018 09:41 AM

Thanks very much bro, appreciate it.

Boston01X5 08-09-2018 10:24 AM

4 Attachment(s)
I went out to car and checked codes in the AC/Heater module, cleared them and these are codes that came back:

Boston01X5 08-09-2018 01:33 PM

Hey everyone,

Time to wrap up this thread for other people who find it. Problem is fixed.

SOLUTION (on my car anyway):

I disconnected and reconnected all the connectors on the panel just to make sure there wasn't a problem with connections to new heater control panel.

I noticed that small 3 wire connector where I tested the ground, when I pushed it in, the female ends, what goes on to the pins -pushed up.

I pushed them down so they were fully seated on the pins with a small screwdriver, and now AC and panel working perfectly, no more rear blower constantly on.

Things are working properly, all because of those these not being fully seated even though the connector was snapped in.

I know this is probably a once in a million solution but that's what fixed my car so wanted to update.

Thanks everyone for the help, Andrew you were very helpful bro appreciate it your a valuable member of this forum.


andrewwynn 08-10-2018 12:10 AM

That's shithot news! I love when it's just a loose wire good times !
You will find it's not very difficult to work on e53. It's my favorite car to work on though definitely can be challenging.

I'm having fits with mine there will be some posts coming regarding my problems soon

Sent from my iPhone using Tapatalk Pro

Boston01X5 08-10-2018 06:30 AM

Can't say thanks enough for your help Andrew and I will look for your posts :) I love the E53 compared to my ML320 :)

andrewwynn 08-10-2018 10:30 AM

Your story is very similar to my first X5 repair.

When I bought it the AC wasn't working.

15 yr old car you assume low freon so I try to add but it's at the static pressure of the can so I figure it was worked on and never vacuumed out so I get the tools to vacuum and recharge including high/low gauges but it won't charge.

I can't get the compressor to activate to suck "freon" from the low side.

Guessing that the low side switch may be defective my plan was to hotwire the compressor to enable filling it.

I never figured out how to pull the connector off the compressor so I decided to measure the Ω on the low side switch.

When I went to pull the low side switch it came off with no effort!

I pushed it on and the compressor started immediately (car was running at the time). Topped off the R134a and got about 50F out the daah. I added a little more a week or so later and about 40 at the dash after.

Now I have the NT510 I can direct read the evaporator temp to help optimize charging vs needle thermometer in the dash.

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