Don't bypass klima/mas unit relay for air fix
10-22-2005, 04:27 PM
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91 300E
Don't bypass klima/mas unit relay for air fix
Now it is an option to bypass the klima unit on the air conditioning end when fixing the air conditioning as a fix in some cases. It does work. I was told the klima serves as the fuel pump relay as well as the climate control relay. Now the procedure works for fixing the air but after a years time certain things started happening here and there. All subsequent problems were fixed with the installation of a new MAs unit which is about 450 bucks with the bypass fix undone and all stock wiring restored. The bypassing created some unexpected errors in the mas unit apparently in effect frying it.
problems after 9-12 months were:
check engine light
fans on full tilt 24/7 (unless this was fixed by replacing the coolant temp sensor which was faulty and replaced at same time)
compressor on 24/7
ec fan pushing colder air than ac
ac not very good at idle or stop and go traffic when temp is over 85F
when driving with all ac or ec off windshield vents still pushed out cold air fogging up windows (compressor always running)
hard start/stall on first key turn
All these problems disappeared after replacing the MAS.
The first shop i had thw work done with when i first moved here was inexperienced obviously and after a fashion errors started occuring related to the fix (hot wiring) I am obviously assuming. Those *******s told me that the reason the cold air was not so good at idle was due to the old system. Whcih in converting to new refridgerant may in part be true but not to the effect that i was experiencing. They also broke and failed to reinstall the fresh air intake. They denied any wrongdoing regarding that affair. Live and learn.
Also 2 months after the air was fixed the fuel pumps both burned out. This was the result of a cut wire causing errors in signals. I am suspect that cut wire was from the work of the shop that fixed the air.
The shop I have now is reliable and run by ex-mercedes techs from the 80's-early 90's.
problems after 9-12 months were:
check engine light
fans on full tilt 24/7 (unless this was fixed by replacing the coolant temp sensor which was faulty and replaced at same time)
compressor on 24/7
ec fan pushing colder air than ac
ac not very good at idle or stop and go traffic when temp is over 85F
when driving with all ac or ec off windshield vents still pushed out cold air fogging up windows (compressor always running)
hard start/stall on first key turn
All these problems disappeared after replacing the MAS.
The first shop i had thw work done with when i first moved here was inexperienced obviously and after a fashion errors started occuring related to the fix (hot wiring) I am obviously assuming. Those *******s told me that the reason the cold air was not so good at idle was due to the old system. Whcih in converting to new refridgerant may in part be true but not to the effect that i was experiencing. They also broke and failed to reinstall the fresh air intake. They denied any wrongdoing regarding that affair. Live and learn.
Also 2 months after the air was fixed the fuel pumps both burned out. This was the result of a cut wire causing errors in signals. I am suspect that cut wire was from the work of the shop that fixed the air.
The shop I have now is reliable and run by ex-mercedes techs from the 80's-early 90's.
Last edited by zahkunst; 10-22-2005 at 04:33 PM.
09-01-2007, 04:27 PM
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'69 280SL, '95 E320 Wagon, '86 Toyota SR5 Truck, '69 Honda Trail 90,
bypassing the klima relay by connecting pins 5 and 7 using a jumper is only used as a diagnostic measure for a short time only. If you leave it connected, you can't shut off the A/C compressor. It runs full bore all the time! Not good! don't do it!
