heater works when it pleases..... any ideas?

Ive had my 3rd hiace for about 6 months now. 2 months after picking it up the heater decided it would work when it chooses, rather then when i choose.

This has been ok during the summer, but now its coming into fall / winter im not keen on the gamble of that with a 60 mile drive to work....

Its a '94 1kzte hiace. I live in semi rural usa (3hrs to city) and am not mechanically "able" although i do have some understanding of how things work. Been learning along the way the past 11/12yrs.

I had my coolant flushed - it was disgusting (last owner clearly didnt look after it) . Looked more like bourbon or old coffee than red coolant.

So i hoped the blast through the heater core would solve the issue.

Fan blower works fine. Ac works always. Heat works 2/3 of the time. Its literally hit and miss whether when i start driving to work whether i will get heat or not....
When it does work heat comes through immediantly as soon as engine reaches temp. When it dosent, it just DOSENT :/

I do live in an area now that gets mild snow, so i obviously want to be able to at least keep the windsheild from icing.

Anyone got any ideas?

I do have a mechanic an hour a way thats willing to work on my van - hoping for some pointers for the poor guy!

Anyone else had the same issue?

this is her......

Check that the cable from the heat / cool lever to the control flap is not detached from the flap thus allowing it to move by itself. (Assuming it's cable controlled like many are, not electronic, if it is electronic then maybe a sticky solenoid).

Decal on the side looks like it says it's the Limited trim, which probably means it has the automatic climate controls, so the cable is actuated electromechanically. So yeah could be solenoid issues, gunk in the valve body that is interfering with normal operations, or cabin temp sensor issues?

When the heat does work, can you adjust the temp control up/down and does the heat increase/decrease accordingly? If it's auto-climate, I think there is a sensor in the climate controls (in the bottom-right of the unit behind a little four-slotted grill) that decides if the cabin temp is below/above the temp setting and adjusts the heater valve accordingly. This could possibly be on the fritz as well. In the below diagram you can see that grill, and there is also another part #87284 called RESISTOR SUB-ASSY, VARIABLE, which may be associated with the temp slider. If this is not working 100%, it might be intermittently sending a signal to whatever component actuates the heater valve.

So heres what happens:

I pretty much just leave the lever on the high heat setting and dont move it. I can start the car and sometimes i will get heat, other times not. I think ive moved it 4 times this year max to use the ac. Otherwise i just open a window or the roof for air because it dosent really get above 65f / 18c where i live.

The other morning for example i didnt get heat, but then when i went to the grocery store after work i got heat when i didnt need it because it was warm out.

Went hiking yesterday at 5am - thank god it was warmish at work that morning otherwise that would have been an uncomfortable 3hr drive as i got no heat. Tried restarting the car 3 times to see. Nothing.

I have the car booked at the mechanic tues next week do replace something else so im trying to gather ideas for them to explore. Im the first and only hiace theyve ever worked on - its small coastal town in usa. Like 12,000 people small.

Are your climate controls manual or automatic?

Does it make a difference if you have the temp slider all the way to the right and you are on the Auto fan setting versus the manual ones?

I'll have to check my owner's manual tomorrow, but in my mind I'd think that using the manual fan settings would interpret the temp slider in the way that purely manual hvac controls do, i.e. directly controlling how closed/open the heater valve is.

This might tell you if the temp sensor is faulty (Auto setting would be flaky, manual settings produce heat), or if the problem is with whatever servo is pulling the cable that actuates the heater valve.

I dont know what the auto setting is in all honesty and ive never used it as it only seems to affect the fan speed nothing else.

I always have fan on full and heat on full.

I know in the photo i have the fan on cool temp - but i was driving back from a hike in 30c temps and the damn heat worked for the once this week and i needed to cool the van ha ha

The Auto fan setting reads the cabin temperature via a sensor and adjusts the heater valve/fan speed to maintain the set temp indicated on the temp slider.

ahh. well ive never used that lol.

You mentioned that previous owner had neglected coolant and it was in really bad shape when it was changed.  From the sound of it... you might have issue with delivery of hot coolant to heater core.  It could be either caused by air bobble in heater core or heater core could be partially blocked.  In either case it would be worth checking it and taking of the suspects list.  You will not need any special tools or knowledge when diagnosing this one.

The control valve which provides flow of hot coolant into heater core is located in front of van, right behind the front grill.  You will need a screwdriver to remove the screws holding grill in place and then remove grill.  You will see there the control valve on one of the two rubber hoses.  Control valve will have controlling wire attached and there will be lever on control valve to open/close coolant flow.  You can verify that control valve is working by having someone inside the van to move heat selector back and forth and you watching if those movements transfer to control valve on hose.  

If the movements are not translating into lever movement on valve, then you will need figure out what is causing it and fix it.  If they do, then you know that heat selector/control on control panel is working.

Now you need to confirm that hot coolant is circulating through heater core.  For that you will need van at operating temp, so drive it for 10-15 min.  Confirm that control valve on heater hose is open and then with engine running touch with your hand hose leading into heater core (hose with control valve) and touch hose coming from heater core (return hose for coolant).   They both should be hot, with return hose a little bit cooler.  If you have both hoses cold or hose on which you have control valve hot and return hose cold, then coolant is not circulating.  If both are cold, move the heat selector to complete opposite... just to be sure that control valve is open.

*If your problem is intermittent, then you as well drive around your regular business with front grill not being installed and the minute your heater stops supplying hot air... you can stop the van (engine running) and go check the heater hoses.

If you determine that heater core is not letting hot coolant to circulate through or is letting circulate intermittently you will need to flush the heater core.  On HiAce front heater core that is very easy to do.  You will need a couple of long nose vise grips, a bit of rags, garden hose with decent water pressure and about an hour of time if you doing it first time.  (If you don't have long nose vise grips, you can make wooden plugs to plug the coolant hoses leading to and from heater core.  That way you don't need to drain the whole cooling system just for front heater core flush).  If you decide to use wise grips, be gentle do not damage coolant hoses when you lock wise grips.  Just close enough to stop coolant seeping out of cooling system.

Once you have closed heater feed and return hoses, then you can disconnect heater hoses in a way that you can disconnect heater core from cooling system.  One end can be right after control valve for example...

A simple way to flush a heater core is as fallows.  You will need to get the garden hose connected to heater core in or out hose/outlet and then run water from garden hose through.  Keep doing that until water runs out of other hose/outlet clean and without obstructions.  Make sure you reverse the flow of water until results are ideal in both directions.  You can variate pressure in garden hose...thus dislodging any sort of obstacles in heater core.  If you can not get it to flow, then you as well consult with your mechanic as he might have special flushing gun where you can use water and compressed air to flush heater core.  

Once you have confirmed that water runs free, you can blow the heater core out with compressed air for any water left behind, but this is "nice to have" not so much required step.

Connect the heater to/from hoses and remove the wise grips or wooden plugs and check your coolant level by removing radiator cap (it should be lover).  Make sure the control valve on heater hose is open i.e. lever on control panel to max heat.  You will need to add some for sure, so make sure you add the same coolant you have in system already.  If you need to add more then a 500ml... your system might have been under filled... so fill it up to the top of radiator cap.  Start engine with radiator cup off and watch if level drops.  If it drops, add some more until it is full and stable.  You can increase engine rpm while doing this.  Close radiator cap when system is not taking it anymore and go for drive. I would try to fill in this way for about 1 or 2 min.

After drive check that cooling system is pressurized i.e. grab any of the big cooling system hoses and check that they are hard.  If they are not pressurizing (hoses are soft), you might have problem with radiator cap or there is a leak in cooling system.  If everything is OK, take a look at radiator expansion tank and either take a mental note on level of coolant or take a picture.  Next morning i.e. engine has cooled completely you can check the radiator expansion tank coolant level and add coolant as needed.  You can also take off the radiator cap and check coolant level that way and add as necessary.  This time engine not running and system is cold.  Once you have checked/added coolant this way, start up your van and go on about your regular business.  Repeat this procedure until system is not taking any more coolant... at this point you should have filled system full.  I would only remove radiator cup for first 2 cycles, after 2nd cycle i would only fill cooling system through expansion tank.

I have seen posts about problems of filling hiace cooling system completely i.e. ensuring there are no air pockets.  I can confirm same issues when I was filling cooling system the traditional way (as explained above).  Traditional way will work, but you will need 5+ heating cooling cycles to completely fill the cooling system through adding coolant to expansion tank.  Also, make sure your radiator cap is working properly and hose going into expansion tank is not with holes i.e. damaged.

Best way of filling hiace cooling system is by using a vacuum type of fill system, but that might be the think you better leave to your mechanic.  There is nothing complicated about it, but you do need access to hi flow shop air and vacuum fill tool kit.

You can look up videos of how to flush heater core on y0utube.  The working principle will be identical on most vehicles and specifics of hiace are above.

Above would be possible for someone who is interested in mechanical things, but is not yet proficient or tooled up for major adventures under the hood.

While you are at it, you as well do the same check for rear heater core if your van has rear heater built in.  My rear heater core got plugged, even I had fresh coolant changed.  I flushed it and it is working fine now.