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Best way to test heating electrical parts?

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

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scot850
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Best way to test heating electrical parts?

Post by scot850 » Mon Oct 02, 2017 1:29 pm

So for those who have been following the repairs on my 'project' V70 SE base, the reason for buying it originally was to use as a test bed for a crap load of heating system electrical parts I seem to have accumulated over the years. I have what some call resistor packs for ECC systems, heater fan units, in line temperature sensors, ECC units and cabin temperature sensors.

I plan to swap the parts into my project car to make sure they all work as they should in a vehicle. But how best to test the units and are there any short cuts I can do to verify items work? A good example is the 'resistor packs'. They are static parts that have no moving parts, so probably no reason to fit them, drive the car and see if they work. But how do you check how they work? Is there a way to fit a unit without taking the car out for a run and test it in a system to ensure it works? Is there a setting on the heating system that will work for this to speed up the process?

I am a couple of planned repairs away from buffing/polishing the paint before selling the car, so want to start the testing ASAP.

Any help/guidance appreciated!

Neil.
2000 V70 R - still being an endless PITA
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Re: Best way to test heating electrical parts?

Post by wizechatmgr » Mon Oct 02, 2017 2:22 pm

Multi-meter on ohms setting would give you a basic indication of status for the fan resistor pack. Anything more advanced you'd need to put a load on it for.
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Re: Best way to test heating electrical parts?

Post by wizechatmgr » Mon Oct 02, 2017 2:27 pm

The ECC temp sensor for the blending I believe is a 2 pin - you should also be able to reference the resistance at a given temp.

The ECC passenger's/cabin air temp sensor has some electronics on it and likely digital signaling so you'd be better off to plug that in to a vehicle to test it.
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Re: Best way to test heating electrical parts?

Post by BEJinFbk » Mon Oct 02, 2017 9:26 pm

The ECC "resistor pack" is more than just a bank of old school resistors
and have a PWM signal fed to it from the ECC that modulates the MOSFET
that actually controls motor current on the negative leg.

Short of lashing up and entire test system with all of the sensors,
actuators and a complete harness, I'd say putting it into a car
with a known good ECC system is the way to go. It's also worth
remembering that it's mounted in a duct with a heat sink for a
reason - that MOSFET needs to be air-cooled when it's working.

Once it's connected, the variable fan speed control in any mode
but AUTO should tell you if it's functional or not. I suspect you'll
find 3 major categories: Fully On Failed, Totally Off Failed or
Perfectly Variable and Just Fine. The one minor possibility
would be intermittent operation, but these ECC power
packs generally either work or they don't.
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Re: Best way to test heating electrical parts?

Post by scot850 » Mon Oct 02, 2017 9:46 pm

Thanks guys for the valuable input. Resistor packs look like the easiest and I will plan to install and test the variable manual speed control to see if they work.

The cabin temp control sensor in the dash by the ECC unit is going to be the biggest pain as I can see it may only be testable in-situ to ensure the little fan motor pulls air over the thermocouple bead. I'll have to test the existing system with a laser temp gauge and then swap each unit in and see if they control the dash air outlet temperature the same way.

ECC units (I think I have 2 off spare) I'm sure worked previously. I thought that someone wrote that the 98 and 99-00 were different ECC units but why would they be? I will need to compare part numbers on the units and see if they work. I'm sure one came from my old 98 V70XC as I thought it was defective but found out it was a bad servo motor instead.

Neil.
2000 V70 R - still being an endless PITA
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2003 Toyota 4Runner V8 Limited
2015 Kia Sportage EX-L
1993 850 GLT -Sold
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1997 Volvo 850 SE NA - Went to niece in California - Sold
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Re: Best way to test heating electrical parts?

Post by abscate » Tue Oct 03, 2017 2:22 am

Neil, the ECC control unit break might be covered in the bastards thread. There was a change mid year in MY99 to a combined damper motor that's documented in the forum

The low pressure switch on ME7 reports to The ECU , not an analog compressor voltage, I'm not sure of ECC control units changed from 98 to 99
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Re: Best way to test heating electrical parts?

Post by sleddriver » Tue Oct 03, 2017 12:11 pm

BEJinFbk wrote:
Mon Oct 02, 2017 9:26 pm
The ECC "resistor pack" is more than just a bank of old school resistors
and have a PWM signal fed to it from the ECC that modulates the MOSFET
that actually controls motor current on the negative leg.
Bingo!
The "resistor pack" myth has lagged on far too long. As BE correctly pointed out above, it's far more involved than that.

Neil, if you want to test I'd suggest an oscilloscope to observe the range of the PWM signal from the ECC. Then you would need to make voltage & current measurements on the output stage of the fan motor speed controller while powered up and connected to the motor itself. Not sure if the motor uses a RPM sensor for feedback to the controller or not.

I too have wondered if these MSC's (motor speed controllers) age/slow down over time, as air vent velocity appears to be reduced compared to long ago. However as ALL AIR travels through the A/C evaporator whether the A/C is on or off, it's pressure drop has to be taken into account. The sled's evap is original and now 20yrs old. It does have a small inconsistent leak. I've just fed it occasionally rather than replace it. A wet evap coil has even more drop, increasing the load on the blower, which pulls more current from the MSC. A partially clogged evap coil will increase this load even more. Over time all of these variables add up.

As to the temp sensors, these are pin-head sized PTC or NTC thermistors. I vs. V vs. T testing (current vs. voltage vs. temp) curve generation will produce a characteristic curve.
1998 V70 T5 226,808 miles. Original Owner.
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scot850
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Re: Best way to test heating electrical parts?

Post by scot850 » Wed Oct 04, 2017 11:04 am

Using an oscilloscope testing process would be great, if I owned one or knew how to use one and determine what the output was telling me. If I was starting a business testing/selling these then maybe the equipment investment and learning how to use one.

I am going to limit this to installing and checking it works at all speeds with an increasing speed. Sure they may not be 100% as a new one, but then when I sell them I will not be asking 100% of a new one either. Few people want to go to PnP to pull these and most don't want to spend the money on an old car for a new part. I have several of these that just seem to accumulate over the last couple of years and now I realise how many I have and don't need more than 1 as a back up of each item as I will end up with only one P80 shortly and the one I have has had all the main items replaced with the exception of the ECC unit itself and the resistor pack.

We probably now all know that the 'resistor' pack is not just that but it has become common speak for the part and most enthusiasts know what we are talking about. I for one though do appreciate the education as I love trying to understand how stuff works, but a lot of electrical stuff is just a black art to me!

Well hope to get started on the in situ testing program by the weekend following completing the replacement of the sealing strip below the tailgate window (that some idiot has glued with epoxy at the ends!!).

Appreciate the input guys,

Neil.
2000 V70 R - still being an endless PITA
2006 XC70
2003 Toyota 4Runner V8 Limited
2015 Kia Sportage EX-L
1993 850 GLT -Sold
1998 V70 XC - Sold
1997 Volvo 850 SE NA - Went to niece in California - Sold
2000 V70 SE NA - New project and test bed - Sold

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