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Discussion Starter · #1 ·
Time to do my bit for the community :wink:

If you have a Diesel it should not be cold in the winter when you start driving. It should be blasting hot air within 30 seconds of ignition on - i.e. much better than a petrol engine. This is because it is fitted with a PTC heater 'wot' you normally find on high end German cars only. The WIKI and other areas of this site provide details of this device.

If your like me and you feel the cold and are currently enjoying the icy blast from a blower running full power when the coolant is cold, read on.

Tools required.

A good Phillips screwdriver
Two 2ft lengths of wire around 1mm core. (One core from household lighting flex is about right)
Multimeter - £8 from Maplins will do just fine.
12mm socket or spanner.

Access:

Remove the center console as detailed in the ICE posts concerned with access to the car stereo unit.
Move the steering wheel fully down and fully out.
Gently pull the "Instrument Lower Panel" section (with the climate control temperature intake holes / slots) directly toward your face. Detach the pipe and electrical connection. Note: you have to push the releasing tang all the way IN for the electrical connector to release. I find two hands are needed one from underneath to separate and one on top to depress tang.

Line art Auto part Drawing Diagram Illustration


Once that's out - there are two Phillips screws which secure the main instrument panel. Thereafter there are a series of clips which as usual must be gently worked loose to release the panel.


After you have got it out a little way - the first connection to release is the 32 pin Climate Control Block. Second the VSA switch - the tang is on the underside and again has to be pushed in a long way to release it - and its right at the place where the wires enter the connector housing. Finally the Starter button switch.

Line art Auto part Drawing Illustration


Now you have access to all the required areas and components.

Remove the starter switch and the Climate Control unit from the instrument panel by undoing the screws holding them in place. Refit the starter switch to its connector.

Auto part Automotive lighting Engine Vehicle Car


This will allow you to start the engine later on in testing. Keep the climate control unit handy (on the passenger seat) where you can easily and quickly connect and disconnect it again free of its normal housing.

Testing:

1.

Firstly you want to test that you are getting 12v at pins 17, 18, 19 of the 32 pin Climate Control connector block. ( Basically the Climate Control unit grounds the current from these pins to switch the respective relays for the PTC heater and therefore allow 120 amps to flow through the core via the main relays (40 amps per relay). )


Ground your multimeter (on a bolt is best) and use the live side of the cigarette lighter to test your meter is performing as expected. Place the positive probe in the number 17 hole and check you are getting 11 - 12 volts with just the ignition on (not running). Repeat for holes 18, 19.

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If that was successful - this tells you that the wires and the signal from the fuse box on the low power side are intact.

2.

Ok, if you are good so far, now you need to earth these pins to close the relays, while you test other parts. Disconnect the PTC connector. Use your lighting flex to earth pins 17, 18 and 19 of the 32 way connector.


Auto part Gauge Vehicle Car Engine

Auto part Engine Vehicle Automotive engine part Electrical wiring

Auto part Technology Vehicle Wire Electronics



3.

Check you are getting voltage at the PCT heater connector.

Background:

Now you have done what the Climate Control Unit should do when the 'on conditions', are met, we can test for a voltage at the PTC heater block connector. The climate control pins have the following PTC heater connector relationship.

17 will close the relay for Pin 1
18 will close the relay for Pin 3
19 will close the relay for Pin 2

Text Font Line Diagram Parallel


The bottom four pins 4,5,6,7 all provide ground for the PTC Heater core. So a quick check that there is continuity between those and ground is worth it.

Procedure:

Rig up the grounding wires as discussed above. Then turn on the ignition. Test for voltage at PIN's 1,2,3 respectively on the PTC Heater Connector.

Auto part Engine Electronics Vehicle Vehicle audio


If you get voltage this tells you that the fuse box and associated wiring, and the fuses in the fuse box are all ok.

4.

Time to get warm!

Switch off the ignition and remove the grounding wires from the Climate Control Connector Block. Refit the Climate Control Unit. Switch on the ignition, set the mode to "face" set the temperature to 'hi' and the fan to about the midpoint. Switch off the ignition and remove the climate control unit again. Re - attach your grounding wires to 17,18,19 of the climate control 32way connector block. Re-connect the PTC Heater connector block. Start the engine - if you remove and re-connect the grounding wires from any of the holes with the engine running you should "hear it". 40 amps is quite a load. Run the engine for up to 1 min and shut off.

Quickly pull the grounding wires and connect the climate control unit and switch on the ignition. Feel the air emitting from the dash vent it should be warm for a few seconds before the PTC core cools from the passing air. If this is the case you have a fully working PTC heater core and an indeterminate issue.

More information on that.

Basically the Climate Control Unit is a small computer. It will only turn on the PTC heater core if:

The resistance from the outside temperature sensor (I am guessing) is about 20 killo ohms or more. Honda don't elaborate any more than saying it needs to be cold.

If the coolant sensor ECT sensor is reading cold.
If the engine is on.
If the air mix motors for both occupants are set to MAX hot and
If the blower is on.

The issue is, that any false readings or unexpected values from those components on which we are depending, will mean the Climate Control Software fails to decide to ground out pins 17 and or 18 and or 19. So it doesn't come on.

The manual only has this to say about the decision process it goes through.

Operation Condition




  • Engine running
  • Blower motor: turned ON
  • Air mix motor: Max Hot position
  • Outside temperature is low
  • The number of operating PTC heater(s) change(s) with engine coolant temperature

What to do? - in my case I can go two ways I think. Bypass the climate control unit with a multi switch for the PTC Heater cores. effectively they will just ground out the low power side of the relay(s). Or I can start adding resistance to the OAT sensor to make the car think its winter and test again.

Anyway - I think if you decide to follow the above (which will take no more than a few hours) you'll get a definitive answer on the cause of your own PTC problem.

Update: Further thinking / investigation overnight has shown that. . .

As far as the Coolant temperature goes, this is fed via two sensors to the ECM module. Thereafter transferred via the B-CAN (Body Controller Area Network) to the instrument gauges and other interested devices connected to this bus. For the Climate Control Unit, PIN 4 reads the B-CAN circuit to derive this data. There is a self test for the B-CAN circuit (which is too much to go into here). Suffice it to say lots of things use this circuit like the central locking, rain / lighting sensor and other things that you would quickly notice not working correctly. There is however, a voltage test that can be performed on the High and Low Voltage ECT Sensors and also on the ECM connector where their signal arrives to ensure continuity and data transfer is happening from the sensors. I may do this tonight, (when I can get access to a ramp as it's necessary to get under the engine to reach the sensors).

As far as the Full Hot position of the Drivers and Passengers Air Mix Control Flap goes - this can be tested with the HVAC self test diagnostic. In my case I can see (MK I Eyeball) that the position of the flaps is full hot demand position and the system reports that this is the case in the self test. So this should be OK.

As far as the Blower being on goes - this can be verified with a transistor test on the blower transistor (this regulates the voltage to give different speeds of operation). There is a test for this listed in the manual and also I want to have the blower out to check inside the air box for debris.
(Gonna do this today before it starts raining.) Have tested blower thermistor and it produces 1.5 K Ohms (bang on).

Finally then the OAT sensor. Removing the bumper gives access to the OAT sensor. Honda list a chart of values for a given temperature 11k Ohms at -5 degrees - 1k Ohm at +40 degrees. 5k Ohms = 5 degrees outside air temperature (OAT). This data arrives via PIN 30 of the Climate Control Unit so a resistance test there is the first port of call before removing the bumper, to do the below simulation.

I have opened a call with Honda UK Technical in Slough this morning, requesting the trigger value (resistance value) from the OAT sensor that the HVAC control software uses to decide that PTC Heating 'IS' an option to be used. I would think its 5 degrees or below - but hopefully we shall get a definite answer.
Seems like plunging that sensor into a glass of Ice water will replicate a cold winters day nicely, if needed!




Disclaimer - everything in here is for info only - if you decide to follow this guide and something goes wrong it's not my fault. Very happy to take PM's on this to help out.
 

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Discussion Starter · #2 ·
So I forgot to mention that I pulled the blower motor out and borescoped the heater box, (to investigate the cause of another heater issue) in fact the recirculation flap (accessible by removing the glove box) is a MUCH easier access option if you ever become crazy like me and want to do such a thing! Getting the blower motor out is a pig as you have to first remove the entire clutch pedal and all the skin from your knuckles. Actually to be fair what's hard is that the instructions do not show how the clutch master cylinder and pedal mechanism separate very well (at all) and there is a fair bit of guesswork and swearing needed before it decides to 'let go'.

Back to business:

I think - I've decided to go both routes I mention in the post above.
Honda have not responded and I am beginning to think they may not.
So this leaves me to do an ICE test on the OAT senor - which I plan to do if I can get some time this weekend to remove and refit the bumper.

But I also plan to make and fit the switch to switch on the PTC heater when I feel like it. Clearly this has some risks of a user doing something silly, like running it too long / too frequently / too hot all of which are safeguarded by the HVAC software which I am going to augment with the switch arrangement. If you decide follow in my footsteps - make sure you have some understanding of how these things work before you bring the control to yourself.

Here are the components required. Cost was about £12

A couple of meters of alarm wire is perfectly sufficient for the loads we will encounter in this project. A knob, the switch and the connector.

Product Water Material property Technology


Plan is to drill a small hole in the drivers under cover and put the switch in that plastic panel. Connected everything to a four way connector block so we can easily remove the panel when required. The post of the switch is length adjustable, via a hacksaw. The knob just grub screws on.

Wiring the switch.

The switch has three terminals in the middle. Each terminal connects to four of the terminals on the outer ring, you can just see in the photo above (switch in the bag). The idea is to wire up each phase of the switch with the required grounding cabling. So there are three relays from the HVAC control unit incoming to the three central terminals. These are always on. In the switches first position there will be no ground wires attached to the corresponding terminals on the outer ring. In the second position, 1 ground wire for the first PTC core. In the third position two grounding wires for the first and second cores and finally three in the fourth position to enable all cores to run.

This means we can limit the spaghetti to the ground side and terminate all seven ground cables neatly at the four way connector block, which will be very close to the switch in any case. Hope that all makes sense if you planning to follow suit.

Cheers.
 

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Was this heater a factory fitted option? My 2.2 only blows warm air after a 4 mile journey. I definitely don't get warm air just after starting. How can I tell if I have one?
 

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Discussion Starter · #4 ·
Take a look in the specs for the Diesel's (N22 Engine) - they ALL have one.
Now I have mine working with the (HVAC control module) bypass switch - it's performance it has to be said isn't outstanding - but it certainly takes the chill off the incoming air while the engine is still cold.

Also:

If you plan to follow my guide I would recommend doing three independent electrical tests on each PTC core for heat while you have it all apart and the HVAC module handy to run the blower after each test.

As I say above the performance isn't that outstanding and this made me re-test to ensure that EACH core was working, i.e. producing heat. They all are and it's certainly MUCH better than before to be NOT blasted with cold air by a computer that thinks the PTC heater is warm already. (if that all makes sense).
 

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It must be getting cooler again (winter is coming).

As mentioned above, all 2.2's should have them.

But the consensus is they aren't great in Civic's and I doubt they work in many cars. They're a royal PITA to check and fix.

Fit heated seats instead, they work REALLY well ;)
 

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Relays

Can you tell me where are the relays for the ptc, ive already checked 4 fuses, but 3 look like relays , in the fusebox under the bonnet,but are classed as fuses how many are there 3 ?
 

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It must be getting cooler again (winter is coming).

As mentioned above, all 2.2's should have them.

But the consensus is they aren't great in Civic's and I doubt they work in many cars. They're a royal PITA to check and fix.

Fit heated seats instead, they work REALLY well ;)
My heated seats take about as long to warm up as my heaters! But when they're on, they're freaking ON!!
 

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Can you tell me where are the relays for the ptc, ive already checked 4 fuses, but 3 look like relays , in the fusebox under the bonnet,but are classed as fuses how many are there 3 ?
The relays must be in fusebox can hear them clicking, also have heated seats
 
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