Need a scan tool with “automatic test mode”

[Squankum]

I’m trying to fix an A/C condenser electric fan on a 2000 Dodge Durango. I’m working off some diagnostic procedures somebody printed from napafix.com a few years ago.

Step one in “tests/procedures” is “With a scan tool, enter the Automatic Test Mode (ATM) test mode and attempt to actuate the condenser fan relay.”


I’m a caveman. Is such a feature found in scan tools that aren’t crazy expensive? Any recommendations?

 

[dclassical]

I believe what you need is a scan tool with bidirectional mode, that is where you can send commands from the scan tool (in your case to actuate the condenser fan relay). Not sure which cheap ones have that... I have an OTC Nemisys and Genysis but they are not cheap.

If I were you I would locate a wiring diagram and see how to activate the relay directly or bypass it (for testing purposes).

 

[Squankum]

Is it a Bad Idea to get at the back of the relay panel to activate the relay directly?

Similarly, is jumping the two main terminals that supply voltage to the fan a bad idea? I've done this with fuel pump relays on Bosch K injection systems. (I'm an 80's caveman.) I could probably even use the same jumper, it's nice, got a fuse and a switch and evertything.

Previous mechanic who poked at this shrugged his shoulders and hinted something about wiring harness or computer (this is 2nd, 3rd hand info, alas) , and, while he's a pro, when it comes to diagnositics, I trust no one and start with basics.

Direct-wired the fan last night, measured amperage draw while it ran, it turns and is well within spec.

 

[Subyroo651]

Dclassical is right about the Auto Test, its essentially Bi-Directional control which is the best type of scanner to have. Unfortunately you cant really touch a good one for less than $1000.
Autel DS708 (~$1,200) would probably be your cheapest option but still a very capable tool.

 

[joe_padavano]

I have an OTC Genisys and yes, it has this feature. I bought mine for $600 on ebay a while ago, but then had to buy software updates. If you buy one, be sure to get at least version 3.0 of the operating system. (the current ones are up to version 5.0, but for a 2000 model year the older version is fine).

 

[MattPersman]

You can just take the relay out of the pdc and jump the 2 terminals to see if it runs at that point you know your wiring from the pdc to the fan is ok. then you gotta find out why it's not coming on from the control side

 

[Squankum]

Thanks, all. I was willing to spend up to $200ish. I'll have need for some kind of scan tool for other coming projects. Dang.

Been staring at the wiring diagram and realizing just how much I can get done/rule out with good old fashioned caveman techniques.

That this thing has a Big Brain running the show just makes me want to get it all right before I even begin to think of blaming it.

 

[shockwave]

Look for a used OTC nemisys best bet at that price with what you are looking for.

But it sounds like the relay is bad very common on chryslers.

You can also jump the fan directly from the battery to see if the motor is good best advice I can give you

 

[devoncoolman]

Does the fan come on with the a/c?? If so then its most likely the temp switch. If not test the relay. Then check ur powers and grounds at the relay. U should have 1 ground 1 all time power. 1 key power and one trigger which will be a ground sent out when the fan is comanded on. That should be a standard relay system. So try switching with the horn relay. That system shouldnt use the failure pron relay that they used in the caravans and jeeps.

 

[devoncoolman]

Oh and ur not gonna find a hand held scanner that can do bi-directional tests. Your best bet is to buy an old out of date snap-on solus. They can be had for real cheap especially if its way out of date

 

[Squankum]

Shockwave and others - I just peeked, and a used Nemisys might be in my future. Thanks!

I hooked the fan up to an indpendent power source last night (spare car battery, harness I built to plug to that connector) and it runs fine, and draws amps well within spec.

devoncoolman - This is just an electric fan meant to run when the A/C runs, keep the evaporator happy and system pressures down. There's an old timey clutch fan on the water pump otherwise. I don't see anything in the wiring diagram about a temp sensor, BUT...

The command comes from the PCM, and I don't know what parameters it's thinking about before pulling the trigger. I've had the impression it was just "driver turned knob to an A/C setting."

 

[treimers]

Been staring at the wiring diagram and realizing just how much I can get done/rule out with good old fashioned caveman techniques.

That tends to work best and teach you the most anyway.

I cannot COUNT the number of "IT engineers" I've worked with in 30+ years
who use all kinds of fancy software and high end network diagnostics tools, and simply go with whatever the tool/software says is wrong.

About 50% of the time, that's just the topmost symptom discovered by the tool or software. There's an underlying reason.
Just today I was working on why some IP phones would not power up
and others would, and the problem moved around the office involved from day to day.

The younger engineer whipped out his Fluke LanMeter and started checking things. He got a couple of cables that didn't test at 100% for each test he ran. So he decided it was patch cables, and tossed out $50 in cables
and started re-wiring wall jacks.

Meantime, I thought it odd that the problem moved around, but was always 4-5 phones working, but never all 12.

So I checked the switch, found the fan running at half speed, full of dirt, checked the power supply stats at the command line, and found that the switch had cut back the PoE power by half because the powersupply was overheating due to it being just as dirty as it's fan was.
Cleaned everything, and re-seated all the connectors.

All 12 phones booted up.
Yell comes from the other room "What did you do! "

I still haven't told him....that his Fluke won't measure dirt....literally...

 

[Squankum]

Having just peeked at CL for some used Snap On Solis, I have to break down and admit:

I like tools,
but I'm not a professional mechanic,
and that's a lot of money,
and damn, what am I, trying to launch the space shuttle here?

 

[joe_padavano]

Been staring at the wiring diagram and realizing just how much I can get done/rule out with good old fashioned caveman techniques.

Yup. The factory manuals are written assuming you have access to all the factory tools, but the reality is that most of the time they are simply doing things like voltage checks or applying 12V that you can do with a VOM or jumpers. As you said, spend a little time studying the schematics and you can do a lot of debugging that way. Despite the desire of most "mechanics" to simply change electronics boxes, the reality is that most problems with new cars are either electromechanical devices (sensors or actuators) or wiring problems (shorts or corroded terminals). Rarely does the ECU or controller go bad.

 

[Squankum]

A question re. the basics that popped into my head the other night:

How can I determine if a ground is good enough? When I measure for continuity with a VOM, should I just look for resistance? Zero is a good ground, iffy grounds will show some resistance?

I could chase down ground connections in this situation and clean them just to be ****, but I’d rather, you know, use the tools and logic to hunt down the actual problem.

Thanks for all the advice, folks!

 

[LEVE]

Are you all talking CANBUS ? If so, isn't that available on some of the DIY Laptop programs and cable sets?

 

[joecon]

the best way to check a ground is to do a voltage drop test. Pos lead on the wire neg lead on the ground the reading should be 0 any thing above .2 is a problem. jump the relay see if the fan runs if it will run see if the relay is getting a trigger voltage go one step at a time.

 

[greasemonkey44]

i went through several controllers for climate control on durangos; stupid thing would not close the clutch til it had a new oem dealer part

 

[devoncoolman]

Too old for canbus. The fan is probably turned on by a high side pressure switch. And thats probably ur problem. Typical problem. Ill have to pull up the schmatic tomarrow at work and see for my self.

 

[jimindm]

I would look for a snap on brick scanner. They are old, and slow in todays world, but there are plenty out there. It would have to be really old that it would not have the OBDII connector and keys.

Dodges have had ATM test modes, I would guess clear back to the introduction of electronic engine management. I remember doing the tests on them back in the late
80s. It is far from something new. I have always been up to date on my scan tools, but I would not be surprised if there was not one in the mid range that would do this test.

You can also buy a set of the relay bypass testers. I think they are around $35 and you get several. Just plug it in and push a button.

Voltage drop test is a good way to check circuits. Many times I just use a halogen headlight for a test light. Works pretty good unless you are working with charging or starting systems. Also not real well for reference voltages, that are usually 5 volts.

 

[1949 caddyman]

Yes you can use a jumper wire on the relay socket wire conector to see if fan runs, then check for power on the supply wire, then use a test lite between the control side wiring to look for signal form PCM.