240D York AC question Help! - PeachParts Mercedes-Benz Forum

Treeman · #1 05-22-2011, 10:08 PM

Here is my homemade schematic, I do not have enough power to kick in the compressor. I have three wires running all go from the box that houses the resistors on to the Receiver/Dryer. The Red one on my drawing is Hot, it light's the test light bright, the pink wire has power but is weak, it lights the test light but nothing like the Red wire, reduced electricity. The other wire has no charge. I have traced these three wires back to the box that holds the three resistors. No breaks found. When I put the test light on the pink wirs I do hear chatter in Resistor A. I swithced it out with another resistor from a 1980 parts car to no avail. Thought maybe the pressure switch was bad and swithed it out as well, still nothing.

The point being AC will not come on, seems there is not enough electricity going through the pink wire to kick compressor on, assuming the pink wire is the problem. I did jump hot wire from the battery to the the 'Junction' compressor kicks in and aux fan comes on. Its getting Hot in Texas and I need you guy's to chime in Please...

meltedpanda · #2 05-23-2011, 10:23 AM

sure your grounds are clean and secure??
Even if you are hook up a direct temporary ground and see what happens

Treeman · #3 05-23-2011, 11:21 PM

bump

thorsen · #4 05-24-2011, 08:18 AM

Your picture is hard to understand, but why do you have the resistors in-line with the compressor? The AC compressor only needs +12 volts to kick in the clutch - aren't those the resistors for the cabin fan?

meltedpanda · #5 05-24-2011, 10:14 AM

did you try the separate ground, hard to help unless you try the things or comment on things suggested- just saying

Treeman · #6 05-24-2011, 12:30 PM

Quote:

Originally Posted by meltedpanda

did you try the separate ground, hard to help unless you try the things or comment on things suggested- just saying

Yes I did seperate all of the grounds and tested them individually and then as a whole all ground points are good.

Treeman · #7 05-24-2011, 12:39 PM

[QUOTE=thorsen;2723282]Your picture is hard to understand, but why do you have the resistors in-line with the compressor? The AC compressor only needs +12 volts to kick in the clutch - aren't those the resistors for the cabin fan?[/QUOTE

I put the pic of the resistors on the schematic to show that the resistor labled A clatters when I touch the test light to the hot wire that is showing lesser voltage, by not lighting my test light up fully. The black line running from the left to the right and up to the resistor box only passes under the box to another junction of wires between the firewall and the resistor box, from there it splits and comes back to resistor A, B and C. Sorry for the pic quality if it will help I will try and make it better but hard to do when using (Paint / bitmap)

meltedpanda · #8 05-24-2011, 02:08 PM

Quote:

Originally Posted by Treeman

Yes I did seperate all of the grounds and tested them individually and then as a whole all ground points are good.

OK good , but I what I meant was to run a separte ground off compressor to known good ground, by pass the others

Treeman · #9 05-24-2011, 02:52 PM

Quote:

Originally Posted by meltedpanda

OK good , but I what I meant was to run a separte ground off compressor to known good ground, by pass the others

Yes I understand, I did that.

Is the only power source to the compressor coming from the switch on the regulator switck attached to the drier?

meltedpanda · #10 05-24-2011, 04:31 PM

thinking out loud here --- if the system is not charged to specs then the pressure switch may not be allowing the "full power" to reach the compressor. Low charge will prevent the unit from coming on at all , but thought that was an on off system. You changed out switch so assume good, but perhaps??? did you check for 12v on both sides of fuse??
Perhaps someone with a 77 AC system can cross check your wireing

Yak · #11 05-24-2011, 08:54 PM

By "resistors" do you mean relays? You may just have a bad relay that isn't closing. A chattering resistor would be odd. A chattering relay means it's not staying closed.

Unplug them, clean the contacts, plug 'em back in.

Treeman · #12 05-24-2011, 09:20 PM

Quote:

Originally Posted by Yak

By "resistors" do you mean relays? You may just have a bad relay that isn't closing. A chattering resistor would be odd. A chattering relay means it's not staying closed.

Unplug them, clean the contacts, plug 'em back in.

DONE

Yak · #13 05-24-2011, 10:31 PM

Quote:

Originally Posted by Treeman

DONE

Does that mean success? Or just done?

Treeman · #14 05-24-2011, 10:41 PM

Does the AC have to be fully charged for the pressure switch to kick-in, thus allowing the compressor to engage? I hope that make sense?

Treeman · #15 05-24-2011, 10:53 PM

Quote:

Originally Posted by Yak

Does that mean success? Or just done?

I cleaned them yesterday and replaced one using a relay I took off my parts car and it made the same noise.
I just dont get it.
I posted a question in the diesel forum asking if the system had to be fully charged to make the pressure switch active sllowing current to go to the compressor.