MK IV losing satellites at random times.

tsaros · #1 04-26-2009, 05:18 PM

Hi,
I have a problem with a MK IV that seems to drop all tracking of the satellites at random times.
By dropping the satellites i mean that the GPS text and the images of the satellites goes away from the screen, sometimes it will come back instantly by itself other times i need to pull the fuse for it to some back.
The unit is tested in two cars, the results are similar in both (one -04 X5 and one -00 e39).

The unit that loses the satellites also has much worse reception than another MK IV unit, this is a bit uncertain however, i might be comparing apples to oranges here since the working unit is currently in a -04 car, and the "bad" unit is in my -00 e39.
I am not sure if the newer antenna in the X5 could make up for the difference in reception strength or not.
The bad unit originally came from the X5, then it started having issues and i decided to test it in my car.

If nobody has a good idea about why the difference in reception is so great then i will try the bad unit in the X5 again during the coming week.
(Did not think about the reception since the problem we knew about when it was in the X5 was that it was losing connection).

I am also unsure if the problems are related or not

I attached two screenshots to show the differences in reception, the cars where parked less then 1ft from each other when i took the images.
Both units use the same firmware (v32).

I have searched but was unable to find something similar to this problem, any advice for me?

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KiwiJochen · #2 04-27-2009, 02:08 AM

Normally I would say the GPS antenna is faulty / weak / dying, and recommend a new GPS antenna.

Note that in your two pictures you have 7 minutes time difference between them, and as GPS satellites orbit the earth, the signals wax and wane with time.
I see satellite 9 disappeared completely, but satellite 26 only dropped from 15.8 to 14.0
And satellite 27 increased in signal from 4.0 to 12.0
Typical indications that the signal is varying as the satellites move along their orbit.

But if you tested the Mk4 in two vehicles, and the problem stayed with the Mk4, then the GPS antenna must be OK. Please ensure that you have the suspect Mk4 installed in the other vehicle for a few days, to be certain that the problem lies with the Mk4.

So if you are confident that the problem is with the Mk4 unit itself, then the problem must lie in the internal GPS receiver module inside the Mk4.
These are very easy to replace, you can buy a new GPS receiver here:
Navigatie-onderdelen.nl | Navigation par - GPS
It's the item labelled as "GPS Tuner"

No special tools or skills required to replace the tuner . as long as you're not a Clumsy Charlie or a Hulk Hogan and treat the electronics with respect and feeling :-)

tsaros · #3 04-27-2009, 03:04 AM

i just noticed that i did not mention that the two images are from the different cars, the fist picture is from the "bad" unit in my e39, and the second picture is from the new unit in the X5.
The unit in my e39 also loses connection with the satellites as i described in the first post, is it likely that this has to do with the internal GPS receiver?

The second picture is there for reference to illustrate how much better reception a new MKIV has compared to the bad unit in my E39.

If you do not advice against it i think that i will go with a new GPS antenna (if there is an updated version since mine was installed in -00) and the new trimbleunit for the "bad" MKIV in my e39.

KiwiJochen · #4 04-27-2009, 11:03 AM

Quote:

Originally Posted by tsaros

The second picture is there for reference to illustrate how much better reception a new MKIV has compared to the bad unit in my E39.

The GPS reception is actually quite similar between the vehicles.

If you look you see that the signal for satellite 18 is virtually identical on both vehicles. And satellite 26 is nearly the same as well. So that means antenna performance is similar. As the photos were taken 7 minutes apart from each other, signals can vary.

Base on the S/N data, I would state that your antenna is OK.
But maybe it is intermittently failing.

You best way forward is, in order of cost and likelihood:
1. Check GPS antenna connector is properly plugged in at antenna and at nav
2. Replace GPS antenna with a new one (cheapest option)
3. Replace GPS receiver with a new one (costs more than antenna)
4. Replace entire nav - if you want to.

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