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Some quick E39 questions.

1911 14
Well, I just purchased a 99' 528i. Manual, Sport package, yada yada yada
Car has 170k on the clock. Runs smooth for the few days Ive had it.

Im pretty car savy, and worked at a BMW dealership ( as a porter ) for a little over a year in FL before moving out to Cali. Unfortunately, its hard to explain problems over the phone.

So i figured i'd just ask here.

1.) AC blew cold when i test drove the car, when i picked it up it no longer blows cold.
Went to charge with the gauge and R134a, as soon as the gauge is hooked to the low side, it goes straight to the red. Seems like blockage or an over charge possibly?

Second question might tie in to prior.

2.) Everything on the gauge cluster seems 'off'. RPM is the only thing that really works well.
Gas - seems spotty
Water temp - seems about right, never goes past OT
MPH - does not work at all
Digital display - MPG stays at 5.9, Temp stays at -40*, MPH ---*---, and miles till empty is definitely inaccurate. Vehicle mileage doesn't change, Trip stays at 000.1
Vehicle schematic - depicts both tail lights are out, although neither of them are.

I read as much as possible online, and seems the -40* usually means the ambient temp sensor is messed up. I looked at it, cleaned it, checked for wire damage, still nothing.
I read the ATS has a correlation with allowing the AC to get cold as well.

If theres anything you guys suggest, please let me know.
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How much did u pay for it?

Sent from my MB502 using Bimmer App
1. A/C charging requires evacuation and recharge with the correct weight of refrigerant.

2. Sounds like a bad wheel speed sensor. Search here for diagonstic help.

The fuel gauge issue might be solved by a treatment of Techron. The level sensors may be flummoxed.

You are correct: unless you sort out the ambient temp sensor, the A/C will not work, and your outside mirrors may get roasted.

THe light control module is sensitive to brass-based bulbs, as well as bulbs at the end of their life. Consider replacing bulbs, and/or examining sockets for dirt or corrosion.
3,600

How much did u pay for it?
1. A/C charging requires evacuation and recharge with the correct weight of refrigerant.

2. Sounds like a bad wheel speed sensor. Search here for diagonstic help.

The fuel gauge issue might be solved by a treatment of Techron. The level sensors may be flummoxed.

You are correct: unless you sort out the ambient temp sensor, the A/C will not work, and your outside mirrors may get roasted.

The light control module is sensitive to brass-based bulbs, as well as bulbs at the end of their life. Consider replacing bulbs, and/or examining sockets for dirt or corrosion.
I figured it to be a wheel sensor at first. I suppose i will have to replace both to get anywhere.

Thank you, I search like crazy. Im not new to cars, or forums. So i try to answer my own questions unless i cant seem to find something in bold i suppose.

Maybe its just an assortment of these things that led me to think they were all the cause of the same thing.

Also, I will have to try the Techron.

If it means anything, I unplugged the sensor and cleaned it a bit and plugged it back in, the degrees has gone from -40 to -38 to -37. Is this still an indication of the sensor being bad?
I ask because i have read you must drive around a bit and it gradually climbs back. If it were to climb back, what does the sensor need to reach before the AC will be able to become cool again? I assume it doesnt cool in order to prevent the compressor from icing over since it ' thinks ' its -40* outside.
In general, it's rare for more than one wheel speed sensor to go bad at the same time - and - you could replace just one - and then if it doesn't change anything - swap it with the other on the same axle.

But I wouldn't do either of those two things. I'd get out my DMM and simply test it. Takes most people about a half hour - most of which is spent in reading this post found simply by typing /wheel speed sensor F3 into the bestlinks:

- Template for responding to the need to DMM check wheel speed sensors (1)

I figured it to be a wheel sensor at first. I suppose i will have to replace both to get anywhere.
I search like crazy.
Make sure you learn how to use the slash key (/) and the (F3) key in the bestlinks and you'll search even less! :)

Maybe its just an assortment of these things
Take them one at a time.

I will have to try the Techron.
Miracle in a can? Maybe. Maybe not.

See this, found by typing /techron F3 in the bestlinks:
Techron additives (1) & how to really clean your gas gauge sending unit (1)

the degrees has gone from -40 to -38 to -37. Is this still an indication of the sensor being bad?
Was it -38°C outside at the time? :)

I ask because i have read you must drive around a bit and it gradually climbs back.
It does act erratically at first. I don't remember when I replaced mine how long it did that. I'm sure it's in the threads though.

I typed /temperature sensor F3 into the bestlinks to find this thread, which my have that answer for you:
- Ambient temperature sensor breaking

If it were to climb back, what does the sensor need to reach before the AC will be able to become cool again?
I don't know, but typing /air conditioner F3 into the bestlinks finds these, which might have the answer:

- How to learn about (1) and set up your air conditioning (1) (2) & how to measure A C temperature (1) & how to remove the IHKA air conditioning control panel to clean the circuit board (1) (2) (3) (4) & how to check the IHKA sampling fan (1) & how to change OBC MID IHKA KTMP temperature from degrees Celcius to Fahrenheit (1) (2) (3) (4) (5) (6) (7) (8)
Yes, if the wheel speed sensor is bad, you won't have the MPG information. The instrument cluster calculates it based on the volume of injected fuel and the distance traveled.

Measure the impedance of the temp sensor with a multimeter. If it is infinite, it's broken. The best would be if you measure it at the back of the instrument cluster. That checks all the wiring to the sensor.

"both tail lights are out"
there are 2 bulbs on each side for the tail light. 1 might be broken.
W
2.) Everything on the gauge cluster seems 'off'. RPM is the only thing that really works well.
Gas - seems spotty
MPH - does not work at all
Digital display - MPG stays at 5.9, Temp stays at -40*, MPH ---*---, and miles till empty is definitely inaccurate. Vehicle mileage doesn't change, Trip stays at 000.1
Well, thank you for the plethora of information.
The majority i read prior to making this thread.

No it wasnt 38*C outside. It was 75*F.
I replaced the sensor ( new OEM ), and checked all wires to the harness. None have any sort of damage.

Driving for a few hours I have watched the temp ont eh digital display go from -37 to -12*F.
After replacing the sensor it was at -40 again, drove for about 30 minutes, and it went to -38*F, again its 75* outside.

The thread for diag pretty much tells me what ive read everywhere. Mostly pertaining to the trifecta people get ( traction control light and ABS).
I dont have that, so if one of the sensors it bad, correct me if im wrong here, it would throw those two lights up IN ADDITION to the MPH gauge.

Long story short, replaced sensor, didnt fix the problem. Reviewed wiring, all is fine.
In general, it's rare for more than one wheel speed sensor to go bad at the same time - and - you could replace just one - and then if it doesn't change anything - swap it with the other on the same axle.

But I wouldn't do either of those two things. I'd get out my DMM and simply test it. Takes most people about a half hour - most of which is spent in reading this post found simply by typing /wheel speed sensor F3 into the bestlinks:

- Template for responding to the need to DMM check wheel speed sensors (1)

Make sure you learn how to use the slash key (/) and the (F3) key in the bestlinks and you'll search even less! :)

Take them one at a time.

Miracle in a can? Maybe. Maybe not.

See this, found by typing /techron F3 in the bestlinks:
Techron additives (1) & how to really clean your gas gauge sending unit (1)

Was it -38°C outside at the time? :)

It does act erratically at first. I don't remember when I replaced mine how long it did that. I'm sure it's in the threads though.

I typed /temperature sensor F3 into the bestlinks to find this thread, which my have that answer for you:
- Ambient temperature sensor breaking

I don't know, but typing /air conditioner F3 into the bestlinks finds these, which might have the answer:

- How to learn about (1) and set up your air conditioning (1) (2) & how to measure A C temperature (1) & how to remove the IHKA air conditioning control panel to clean the circuit board (1) (2) (3) (4) & how to check the IHKA sampling fan (1) & how to change OBC MID IHKA KTMP temperature from degrees Celcius to Fahrenheit (1) (2) (3) (4) (5) (6) (7) (8)
Ok i suppose i will have to test from the back of the cluster next.

No bulbs are broken i have checked and double checked.
Yes, if the wheel speed sensor is bad, you won't have the MPG information. The instrument cluster calculates it based on the volume of injected fuel and the distance traveled.

Measure the impedance of the temp sensor with a multimeter. If it is infinite, it's broken. The best would be if you measure it at the back of the instrument cluster. That checks all the wiring to the sensor.

"both tail lights are out"
there are 2 bulbs on each side for the tail light. 1 might be broken.
Pulled the negative cable off of the battery, let it sit for a minute, and reconnected it.

Started the car and the temp was at 90* and dropped to 85* as i drove around ( accurate )
AC now works fine.

Now to do this damn wheel sensor.
Speedo runs off of left rear wheel sensor. Inexpensive & easy.

Temp sensor probably damaged, pointy thing under front right bumper. eBay low cost & easy.

False bulb out is hi resistance loop, solder ball on bulb smashed, reflow with solder iron or replace.

Time anyway to replace fuel pump.

Replace plugs & cps. Replace cvv & clean icv & maf. Also replace rubber tube to air pump valve.

Switch to npg+ coolant immediately.
Alright cool.

Will have to get that stuff done this week.

Also read that the fluctuation of the car running cool on the highway is the thermostat gone bad.
Their default when bad is stuck open. So I'll probably do that as well.
528 default is stuck closed for 97
Well mine is 99. Gonna replace it anyways just to be safe.
528 default is stuck closed for 97
a bad sensor will cause the gas gauge to act like it is possessed. when mine went (sensor on driver's side rear), the gas gauge was off, along with a bunch of other things that were mentioned earlier by others
Ok guys, sorted most of these problems.

Running cool was due to the thermostat just like i thought. Replaced and now stays pegged at operating temp.
AC problem was the ambient air temp sensor

BUT still my MPH, MPG, Mileage, and trip will not work. Cleaned and replaced rear wheel speed sensors new OEM.
Not throwing any lights such as ABS or DTC. Checked all fuses...all are good.

Even did the Cluster test in Test option 2.1 and EVERYTHING WORKS FINE IN THE TEST!! What gives...

Really bugging me since ill be going on a long trip soon.
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