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  #1  
Old 08-23-2008, 12:49 PM
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Location: Oklahoma
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Troubleshooting cruise control - what meter do I need here?

I am trying to fix a cruise and the following is from GDL's web page regarding a test of the actuator:

"Use a current-limited 13.8 Vdc Power Supply with a series DC Ammeter. Connect between pins 4 and 5 of the actuator plug. The motor should spin (audibly) and be relatively quiet, smooth and strong, current draw about 130 mA dc. It should not rattle, chug, make excessive noise or draw high current. Reverse the connections to pins 4 and 5 and test spin the other direction."

Can someone tell me exactly how to this? I do not have an ammeter, or a 13.8 volt power supply - what exactly do I need here?

Thanks.

ryan

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1984 300D
1972 250
1986 560SL
1991 300CE
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  #2  
Old 08-23-2008, 02:29 PM
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Well I imagine you could use the car battery as your test voltage supply. You have to insert a 1/4 amp fuse into the test circuit though. I do not think the 13.8 volt test supply is critical. The 12.5 volts from your resting battery is close enough for a good function check. Remember to remove both cables from the battery before using it as your test supply.

That way there is no possibility of a harmful overload being applied to the unit. That 1/4 amp fuse should blow at 250 milli amps. Unfortunatly a 1/8 amp fuse is only usable to 125 milli amps. Still might handle the load though. This is effect becomes your current limiting device. You go higher than the fuse current rating and it blows. Probably a glass fuse is the easiest way to get one of this value.

Up to ten amps testing function is incorporated into most reasonable priced digital meters. You also install your meter in series with the test leads and fuse.

I hope this helps and is exactly what I would do if I were testing my cruise controls activation servo unit. You are protected by the fuse and the car battery will provide a constant current/voltage supply for all practical purposed at that extremely low current draw. The slightly lower voltage may give you a 20 milli amp or so increased current flow in the servo and maybe not. Either way there is no concern.

You have to adapt what is available when possible in life. A current limiting power supply is pretty pricey for such a simple check. Substituting what I suggest is practical and cost effective. We are not doing rocket science.

Last edited by barry123400; 08-23-2008 at 02:48 PM.
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  #3  
Old 08-23-2008, 07:58 PM
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Join Date: Feb 2003
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That's kind of what I was thinking, but I'm not sure about the "specifics".

How do I get a fuse into the test circuit - and how do I get the ammeter in series with the fuse and the test leads?

ryan

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1984 300D
1972 250
1986 560SL
1991 300CE
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