Any do's or dont's on replacing these....its down to -30d tonight and brother in-law has no heat in his truck and in the good ol state of South Dakota and all the snow we have...a good 4x4 is needed, this is his only 4x4 too....can you give any tips? we tried to flush it today...no go.....
Thanks everyone!!

Are you saying it's blocked or is it leaking?

To replace it requires pulling the dash back to remove the HVAC box.

If you've never done one before plan on spending 6+ hours doing it.

we think it is blocked.......he has flushed it in the past but this time he thinks he is just going to reaplce it...does not really want to take it to a dealer because of "cash funds" but not really sure he want to take it on himself......

When you say "flushed" did he back flush it as in reverse the flow to push the stuff that would be blocking it out?

He does have enough antifreeze in it so it's not frozen correct?

Yes, it requires pulling the dash back.
You will NOT get it out any other way

A newbee doing it by themselves will be a full day easily.

2 people who know what to do and what not to remove can do it in under an hour.
There not a hard job, but you have to pay attention to what your doing.

Me and a buddy of mine did my 2000 rams evap core in 45 minutes, and that includes reclaiming and recharging the a/c

The ram requires removal of the dash to replace the heater core. If it is not leaking I would try to flush it. My son just bought an Audi a4 and these are known to have issues with blocked heater cores. The solution that I found on the Audi forums is to back flush the core and use CLR Calcium, Lime Rust remover from Home Depot or Lowes. I have used Prestone radiator flush as well to clear out a severely plugged GM radiator after someone mixed green and red antifreeze but that is another topic altogether. CAUTION if you read the fine print on the CLR bottle it says not to use on aluminum or brass. I believe that this is because it will discolor the metal. I went ahead because there were so many good results posted and I was only going to leave it in for a limited period of time. I picked up some heater hose and used a garden hose repair kit to attach a female garden hose end to one side and connected the other side to the outlet of the heater core. Another length of hose from the inlet to the heater core to a bucket. Ran the hose and filled and emptied the bucket a few times and good amount of sediment came out. Next i lowered my compressor output to no more than 20 lbs. Remember the system is designed for 16 lbs and used an air nozzle to blow out the remaining water. Using a small funnel I poured the CLR unto the heater core until it came out the other hose. The directions called for a 50/50 CLR water mix but I figured any water left in the core would dilute it enough. I let it stand for about an hour and started flushing again. I alternated between water and low pressure air until the sediment stopped coming out. (AGAIN I caution about using air pressure, if the core is on its way out you will have a leaking core when you are done, this happened on a Firebird that I was trying to de-sludge but at that time I did not think to reduce the pressure and was forcing water through at 90 lbs of pressure)
From there top off the heater core with antifreeze, reconnect the heater hoses, check coolant level and hopefully you will have heat.
Scott

"remove the dash" is a relative term. You need to pull the kickpanels, you need to remove the ABS sensor and bracket, you need to drop steering column onto front seat. You need to loosen the bolts behind the kick panels that hold the dash in place.

The dash will rotate out towards you. At this point, I connected a strap to the dash frame, ran it through the pull on the upper frame of the door, then over to the rear door and cranked ituntilt he dash lifted high enough for me to get the heater core out.

I had never seen one before and did it alone in about 4 hours.