603 aux fan switch? - Page 3 - PeachParts Mercedes-Benz Forum

gsxr · #31 10-10-2018, 02:04 PM

Note the recent poster (JHZR2) vehicle list shows a 1991 350SD, which has a completely different control system than a 1986-1987 OM603. Need to figure out the chassis in question.

A later model will have the resistive sensor, not a switch, so it gets more complicated.

JHZR2 · #32 10-10-2018, 06:39 PM

Quote:

Originally Posted by gsxr

The control system changed as of USA model year 1988, IIRC. 86-87 use a simple switch, 88-up use a sensor, not a switch (there is a difference).

We can't answer your question without knowing the year & model of your car.

Quote:

Originally Posted by gsxr

Note the recent poster (JHZR2) vehicle list shows a 1991 350SD, which has a completely different control system than a 1986-1987 OM603. Need to figure out the chassis in question.

A later model will have the resistive sensor, not a switch, so it gets more complicated.

Concur.

1991 350SD

Trying to make heads and tails of what I have, and more specifically, how to force on as a test when I’ve got multi-pin sensor/switches.

What Ive got is photographed here:

Learning about the 603 3.5

wwii · #33 10-10-2018, 11:06 PM

Quote:

Originally Posted by JHZR2

Is there a drawing or depiction of what should be jumpered on that?

I’m just not fully read in to the operational philosophy of the switch - I assume there’s 12V in and then two switches that get 12v to two relays or actuation points?

Not sure if the presence or lack of 12v causes a compressor shut down?? Or do those switches close one contact at one temperature and open another at a different temperature??

This is from page 128/3 the Electrical Troubleshooting Manual which is the drawing for a 1990 350SDL 126.135 - Yours probably has two fans (?). I don't know why it doesn't specify the 126.134 also:

At the end of that manual, there are component location hints

The manual can be found here: https://www.startekinfo.com/StarTek/outside/12253/program/matrix.htm

JHZR2 · #34 10-11-2018, 07:57 AM

Quote:

Originally Posted by wwii

This is from page 128/3 the Electrical Troubleshooting Manual which is the drawing for a 1990 350SDL 126.135 - Yours probably has two fans (?). I don't know why it doesn't specify the 126.134 also:

At the end of that manual, there are component location hints

The manual can be found here: https://www.startekinfo.com/StarTek/outside/12253/program/matrix.htm

I appreciate the link and screen shot. I was reading through all this last night.

My query remains the same though, what do I jumper to actuate the fan? And how does it change if it's a sensor or switch?

wwii · #35 10-11-2018, 10:26 AM

Quote:

Originally Posted by JHZR2

...what do I jumper to actuate the fan? ...

Be careful if you are messing with the 12V, wear some non-conductive gloves and maybe safety glasses. No arcs and sparks please.
Looks like if you can turn the fan on by (using the labels on the dwg):

Shorting across the refrigerant pressure switch's connector, X(S32)
taking pin one of that connector X(S32/1) to ground - notice it's wire color is BR/BU.

When you first disconnect X(S32) you should see 12V at pin 1 - if not K10's coil is bad or connectors are bad

If you are energizing K10 by shorting across the X(S32) connector or taking it's pin one to ground you should see 12V at:

K10 pin1 - if not, K10 contact bad or connector problems
both sides of R15 - if not, connector problems or R15 open
at the fan's connector (R15 side) - if not, connector problems or R15 open

JHZR2 · #36 10-12-2018, 12:29 AM

Quote:

Originally Posted by wwii

Be careful if you are messing with the 12V, wear some non-conductive gloves and maybe safety glasses. No arcs and sparks please.
Looks like if you can turn the fan on by (using the labels on the dwg):

Shorting across the refrigerant pressure switch's connector, X(S32)
taking pin one of that connector X(S32/1) to ground - notice it's wire color is BR/BU.

When you first disconnect X(S32) you should see 12V at pin 1 - if not K10's coil is bad or connectors are bad

If you are energizing K10 by shorting across the X(S32) connector or taking it's pin one to ground you should see 12V at:

K10 pin1 - if not, K10 contact bad or connector problems
both sides of R15 - if not, connector problems or R15 open
at the fan's connector (R15 side) - if not, connector problems or R15 open

I'm not so sure I should see 12v at pin 1. If I did, when the switch closed there would be a short to ground. The other pin of s/32 is ground. Or I guess there's a substantial resistance in series with the inductor in the low speed relay?

wwii · #37 10-12-2018, 09:56 AM

Quote:

Originally Posted by JHZR2

I'm not so sure I should see 12v at pin 1. If I did, when the switch closed there would be a short to ground. The other pin of s/32 is ground. Or I guess there's a substantial resistance in series with the inductor in the low speed relay?

The relay coil does have some resistance, S32 controls the relay by switching ground.

I posted the other half of that diagram in your other thread - you can see that K10 pin 4 comes straight from a fuse and you should be able to see 12V at the switch connector. Anyway in that other thread you said you jumpered the switch and the fan came on so all's good.

JHZR2 · #38 10-12-2018, 11:23 AM

Quote:

Originally Posted by wwii

Anyway in that other thread you said you jumpered the switch and the fan came on so all's good.

I do very much appreciate you providing the screen shots and link. Ive downloaded the fsm for electrical.

But I’ve not jumpered anything. So I’ve not yet resolved or started to troubleshoot.

I bumped this thread because amongst other info, it provides part numbers and temp settings.