A/C problems in a 300TD

[bigrichard]

Symptoms:
Condenser fan does not come on. I tested fan with 12 volts and it works fine.
12v at one of the plugs on the drier (the one with 2 wires on the connector) when system switched on (and motor running)
Jumped plugs on drier and still no fan workie
Compressor comes on when it wants to. Can rev the engine and often hear the clutch click but not engage. Clutch does engages occassionally.
There is charge in the system (and oil)
Fuses are good.
I swapped ACCs with a good used one and still get same symptoms.
When the compressor runs while driving, the system does produce cold air. I don't operate it in traffic since the condenser fan is not working.
Ideas?

[leathermang]

Is your car a Wagon ?
What year is it ?
Be sure you jumped the correct plugs on Rec/dryer....

what do you mean by this ---"I swapped ACCs with a good used one and still get same symptoms."

Is that the stuff in the dash ? How do you know it was good ?

Have you checked any of the solinoids in the system ? Can't think of the usual name for those... switches which control larger currents by use of a smaller one.... ( and don't any of you say transistors either )....the fan is probably controlled by one....oK, thought of it.. electromagnetic relay.....

[bigrichard]

Originally Posted by leathermang

Is your car a Wagon ?
What year is it ?
Be sure you jumped the correct plugs on Rec/dryer....

what do you mean by this ---"I swapped ACCs with a good used one and still get same symptoms."

Is that the stuff in the dash ? How do you know it was good ?

Have you checked any of the solinoids in the system ? Can't think of the usual name for those... switches which control larger currents by use of a smaller one.... ( and don't any of you say transistors either )....the fan is probably controlled by one....oK, thought of it.. electromagnetic relay.....

It's an 85 Wagon. I swapped the push button panel with one that I was fairly sure worked.

[TomJ]

Originally Posted by leathermang

Is your car a Wagon ?
What year is it ?
Be sure you jumped the correct plugs on Rec/dryer....

what do you mean by this ---"I swapped ACCs with a good used one and still get same symptoms.".....

As Leathermang stated, you need to short the HARNESS wiring, not the wires coming from the sensor on the dryer. Short the two harness wires that conn to the sensor on the R/D and see if the fan works (it should no matter what condition the A/C is in.)

Also, for the ACC, even bad ones should operate the A/C when the Temp wheel is all the way to cold, the fan switch is manually on high and full operation is selected (button next to defrost.) All the bad units I've repaired at least still worked in manual operation. I'd suspect something under the hood. Try the fan jumpering as explained above and LUK what you find. If nothing else, we're getting into summer, you should be able to supply 12v to the fan so it's on all times while running.

Good luck.

bigrichard,

I'm a little confused. You say you don't operate it in traffic because you don't know if the fan comes on. You won't KNOW if the fan is coming on UNTIL you are in traffic conditions. It only comes on in the event of excessive high side pressure in order to prevent damage to the a/c system.

In a mild climate (since you choose not to list your location I have no idea what your climate is) it would be possible for a properly working aux fan system to live its life without ever coming on.

Go to the high pressure switch at the r/d, disconnect and short the pins on the connector to see if it comes on. If not the problem is with the wiring between there and the fan. If it does, and the fan still does not come on at the specified high side pressure, then the high pressure switch is bad.

BTW, I don't remember which one, but I think that it is the high pressure switch that is actually a temperature switch. In the a/c system pressure is indicated by temperature, so they use a temp switch to sense excessive high side pressure.

Good luck,

[TomJ]

Originally Posted by LarryBible

....
BTW, I don't remember which one, but I think that it is the high pressure switch that is actually a temperature switch. In the a/c system pressure is indicated by temperature, so they use a temp switch to sense excessive high side pressure.

Good luck,

Yes, that's the fan switch at the R/D, a simple potted thermistor. Lots of people short the thermistor wires (which does nothing when D/C'd) instead of the harness wires that conn to the thermistor.

[dannym]

Originally Posted by TomJ

As Leathermang stated, you need to short the HARNESS wiring, not the wires coming from the sensor on the dryer. Short the two harness wires that conn to the sensor on the R/D and see if the fan works (it should no matter what condition the A/C is in.)
Good luck.

You also have to have a good relay.
No relay No fan.

danny

[TomJ]

Originally Posted by dannym

You also have to have a good relay.
No relay No fan.

danny

Yes, relays do go out, but not very common (at least the A/C power relay) since A/C is an intermittant use thing. I pull these relays whenever I'm at the yards so I have a ton of them, email if this is what turns out to be bad. FWIW, I've never seen the A/C relay be the problem with a non working fan, but it's a possibility.

[bigrichard]

I rechecked the high pressure switch by jumping the two wires and the fan does work. Apparently, I didn't have good contact the first time I tried to jump them.
So the next move is to replace the pressure switch, then I'll check out the intermittant compressor issue.
Thanks all for your advice.

[whunter]

Originally Posted by bigrichard

Can rev the engine and often hear the clutch click but not engage. Clutch does engages occasionally.

Sounds like clutch air gap may be too large.

Use a feeler gauge to check the air gap.

[bigrichard]

Originally Posted by whunter

Sounds like clutch air gap may be too large.

Use a feeler gauge to check the air gap.

What should it be? Can I adjust it or is this an indication of the need for a new compressor? How does this relate to the condenser fan, if at all?????????

[leathermang]

Have you found the condensor fan relay and checked it ?

[bigrichard]

Originally Posted by leathermang

Have you found the condensor fan relay and checked it ?

Where is it? Is that the fused one on the passenger side under the dash?

[dannym]

Hey,
It would help if you put your vehicle make and model and where you live in your profile.
The relay, at least in my car, is in the fuse block. It's the front right and the one directly behind it is the compressor clutch relay.
They can be either silver or black in color.

Danny