After reading about various failures of the OEM Tyco branded Airmatic compressor relay problems. It seems that over time the Tyco relay contacts stick together causing the pump run continuously eventually burning up the air pump. A Hella brand relay is recommended as fix, but no specifications of the Hella relay are ever given. The pin configuration of the Tyco relay is common, actually very common, if you search for Bosch relay on the net, it will come up with many circuits and specification for a Bosch relay. Typically, Bosch style relays are used in the aftermarket car stereo business to control everything from fog light, fans, and alarms. I have been using Bosch style relays for over 20 years and have never encountered contacts sticking together and really have not seen a real failure if used within the max. current limits.

The Bosch relay is typically rated at 30 amps for load control, the Tyco and Hella relays most likely have contacts rated at 40 amps. So a basic Bosch style relay will not work.

I've replaced my Tyco with an 80 amp rated relay in the same basic configuration.

I found mine on Ebay, look for 12v 80 amp relay, there is even a 100 amp relay in the same style. If you can find a SPST type otherwise you will have an extra terminal that you will have to to remove by bending it back an forth.
The cost is around $5 if you buy more than one.

Here is a side view of the relay, a bonus is that it also has a LED inside that lights up when the relay is active.


Here is the bottom view of the relay I have, I had to remove center pin or terminal. Use needle nose pliers and bend the center tab back and forth until it breaks off. This will not damage anything inside of the housing.



An finally, here is a picture where the relay goes, under the hood, passenger side fuse box. Note the LED is on as I was testing it by using the "raise" button to activate the compressor.

 

Great write up!'

Can you post a general under hood photo that's zoomed out, showing exactly where the fuse box is located

 

 

I wonder if this could be the cure to my problems. I've had my airmatic pump replaced three times in the last week at the dealership. They also replaced the relays but for some reason my airmatic pumps continue to run aster I turn the car off.

 

If the dealer has replaced both the pump and relays, but the pump continues to run. I don't think the relay is sticking causing the pump to continue to run. I would guess some sort of pressure sensor is not letting the pump turn off when the air tank is filled up. Or there is leak between the pump the and the tank.

When you get the car back from the dealer, what happens? Does the airmatic system function correctly for a while then the pump burns itself out? Or has the car been at the dealer?

 

I've gotten the car back from the dealership twice now within a weeks time. The dealership is saying there aren't any leaks and everything is fine but once I get the car home and turn it off I hear the pump running continously, funny thing is the airmatic system still works, it's just something causing that pump to run.

 

As long as there is air in the holding tank, the airmatic system will function as normal with the ignition on. With the ignition off, it is still active, but usually only lets air out of the system when you open the door. The pressure is restored the next time you start the car. The pump should only run with the car running in normal operation.


If there are no leaks, then most likely it is the pressure sensor or related part. Unfortunately, I am not familiar with all of the individual parts and locations of the airmatic system. If the dealership feels confident to release the car to you, then the system must cycle correctly after they replace the pump and relay.

If the relay is sticking, then there is a bigger problem in the system. The pump motor must draw significantly more current through the relay to cause it to stick. Since the pump has been changed out multiple time then it is not the pump itself. Possibly something in the power harness that is shorting while the the pump is on. This would cause more current to pass and the relay then could stick. This big guess...

Things you can check...

If you able to pull the relay out of it's socket while it continuously runs, the pump should stop. From my posted picture of the bottom of the relay... You can do a continuity check between the lowest pin (vertical) and the top most pin (horizontal) to see if it is shorted. Unfortunately, if you pull the relay, the physical movement may unstick the relay after it is out making this test useless.

If the relay is not shorted, you can also do a voltage check on the relay socket between on the middle row between the outside vertical pins. If there is power on these pins with the relay out, then externally, the relay is getting power. This power should go off when the tank is full. This is why I suspect the pressure sensor.

You can put the relay in and out to see if the pump continues to run. As you do this you may be able to hear the relay click on/off. The pump should not run for more than 10's of seconds if everything is okay. Obviously, if the tank is somehow emptied, then the pump will run longer to fill it up. Do this with the ignition off first, if the pump runs, then something is very wrong, if not start the car, and see if the remove and replacing the relay turns the pump on/off. If the pump starts up, leave it in to see if the it stops. Although the pump may already be burned up.

If the dealer just removes and replaces the pump and relay, they are really not doing any diagnostics. The STAR diagnostics should be able to indicated a pressure sensor issue, but possibly not a wiring harness issue that causes excessive current.

 

Thank you for your reply and I apologize if I came in andkind of got your thread off topic.

I just got off thephone with my service advisor at MB He said the car was running fine throughall of the test and when the technician went to park the car and have itcleaned up to be released to me he noticed the Airmatic compressor was stillrunning so he pulled the battery.

The service advisor now has the shop foreman on the car, theforeman said he check the relays this morning and everything was just fine nowthis afternoon he’s noticing that the relay is possibly the issues as it’ssticking. I asked if they had actually done a star diagnostic and he said yesand that the diagnostic is coming back with no errors or faults. As of now they’re telling me they want tofocus on the relay as they feel there’s an internal issue. I’m hoping they can resolve this in a not toocostly manner as I just purchased the car and have no warranty L

 

No problem... The only reason why I posted this relay topic is because I have heard about the Tyco relay sticking. This is perplexing to me because cars of all manufactures use relays.

Anyways, my theory is to use a relay with basically double the contact current capability to prevent sticking. My car is out of warranty and I do this at my own risk. Since you are working with the dealer and most likely the work has some warranty duration, I would probably not replace the relay as not to void your warranty. Anything that is not OEM is always a red flag.

If the whole issue turns out to be the relay itself, I would ask if there is an alternate brand that is available via the dealer parts department. From memory, there is a Hella brand relay with the same specifications that others have used to replace the Tyco brand.

 

So the dealer has replaced the pump three times but didnt change the relay ??

If so that's clearly the issue !!

 

What was the final outcome?

 

I actually have my car back now and knock on wood, no issues. The dealership put their shop foreman on my car who came to the conclusion that the relay was indeed the issue. My response to this was how could it be an issue if you guys replaced it three times already. He assured me that everything was fine with the relay before he checked it. So they replaced the relay and now all is well. I'm going to order the relay that you recommend and have it on standby.

 

Wow! Glad everything was sorted out.

 

Very interesting that they didn't change or suspect the relay until so late in the game.

The indy shop I deal with said whenever they replace a pump, they automatically change the relay too. I asked if this only applied to pumps that came burned out (kept on running) and they said no, they even replace the relay if the pump was dead.

Basically any pump job includes a relay.

I think they mentioned something about also replacing the relay if they do a bunch of struts (maybe a pair of struts) but I don't recall the exact conversation.

I treat the relay as a maintenance part.. replaced it every 2 or 2.5 years no matter what. Why let such a cheap part either a)strand you somewhere or b)fail and blow up your expensive Airmatic system?

 

So would you recommend me installing this over the Hella relay?

 

The main reason to use a relay with a higher contact rating would be to reduce the possibility of the contacts sticking or burning out due to excessive load. Clearly the Tyco brand uses contact material that sticks over time or when stressed.

The Hella relay has the same contact rating as the Tyco, most likely 40 amps, typical of this style of relay. If you uncomfortable using an "off brand" relay, then the Hella is the way to go.

As indicated in the previous thread, you can consider the relay as consumable and replace at regular intervals.

 

But there really isn't anything wrong with using a "off brand" realy.. or is there?

 

No, it your comfort level... Thousands of offshore relays used throughout the car audio and alarm business in the US and abroad.

This OEM used Tyco issue seem to be an anomaly for MBZ and the Airmatic system.

 

Thank you for an interesting discussion. I would recommend replacing the filter of the airmatic pump as well.
http://www.benzworld.org/forums/w220...ce-filter.html


Daniel

 

Airmatic pump intake filter, that is a great link! I saw in other posts that that there was a filter but did not know if there was a replacement interval. I have a home air compressor moisture trap/filter that I was going to modify to be used in place or before the OEM one. The post provides the necessary details I need!

 

I installed my relay just now.. I installed it and then I raised the car to see if it worked by looking at the green light. The car wasn't giving me any error messages, but I only saw the green light turn off and on very quickly. I thought one of the two I bought was bad, but I put the second one in and the same thing happened... should I be driving the car?

 

A couple of things...

This may be okay and a good thing, the car will raise and the pump will not go on immediately when the tank is full. You may have to raise/lower, raise/lower a few times to deplete the tank to get the pump to run longer.


Did the car raise when you activated the switch?

Since the pump is nearly brand new can you hear the pump at all when it is on?

With the the stock relay can you hear the pump and see/feel the car raise with the switch?

If the car raises, then the relay is working. The duration the pump is on may be shorter than before because it is pumping air more efficiently making it hard for you to see the LED being lit while active.

If you still want to see the LED active, you should stand outside of the car and have someone else active the raise/lower switch as you observe.

To test a relay operation outside of the car, you can apply 12v to the pins labeled 85 and 86. The LED will go on when the voltage is applied. You will also hear a click.

 

Yes, the car does raise and lower. Would I be getting any error messages if the relay wasn't working?

I can hear the pump. It's usually two short bursts.

 

Problem with Airmatic.
I have a 2005 S 500 base. I drove and parked the car and noticed smoke coming out from under the hood from under the passenger side headlight. The airmatic pump kept running non stop, until it burnt out. I replaced the pump, and relay (all new MB parts). Now it will not work at all. I have tried everything but it still shows " Airmatic problem visit workshop", and will not raise or lower the car. I do not even hear or notice the pump running. Any help will be fine.

 

Have you replaced the fuse? My dealer recommended that the 40A fuse should also be replaced after my compressor burnt out in the same way as yours. It was indeed blown.




Daniel