2nd May 2009, 12:15

My A/C is working fine but I cannot get the A/C to blow through the center vents. It will blow from the top (defroster) and the bottom vent. Any suggestions to this problem? All the controls seem to work fine. 2002 Mitsu Diamante.

4th May 2009, 08:43

I commented above on March 24th with the transmission problems and the April 7th and 8th. I can tell you exactly what the problem is, as this was another problem I had. This is a very easy fix. There was a bulletin sent out by Mts regarding this problem and how to fix it as this happened on my 2001. There is some linkage that opens and closes the door that allows your A/C to go to the different vents. They simply need to add a screw or something to hold the rods together. I would check with a dealer to pull the bulletin. It was a simple fix and I was not charged for it. KM.

28th May 2009, 08:00

It sounds like your computer control was damaged by the leaking heater core. This is located directly under the heater core. Welcome to the Club of defective design and parts by Mits. KM.

10th Jun 2009, 13:48

I bought a 2003 before I read this listserv. Too bad. Now when I pull back the passenger side carpet I see no moisture but a lot of green powder. There is the faint odor of antifreeze too. I ran the car for 1 hour (heater at 90 degrees) with the carpet pulled back and saw no drips or vapor. Windows don't fog either.

Is there any place to look to see if the problem may have been fixed? I guess if I can't determine if it was fixed, I'll replace the gaskets just to be sure.

Is the TCU ECU in the main ECU below the heater core? My tcu off light comes on after a few minutes whether I am driving or not. All wheel sensors are OK and the ABS works so the TCU-ECU is suspect. I just can't find a separate box.

I'm not too happy with this Diamante. My 94 went 22K before I gave it away.

11th Jun 2009, 20:25

The green residue you see around the passenger side carpet, along with smell of burnt maple syrup, are the tell tail signs that either the heater core gasket was or may still be leaking. Are you able to contact the previous owner to find out for sure if it was fixed? I have an '02 VRX and repaired my own leaking heater core last fall. It's not that hard to do it if you mechanically handy, and doesn't require tearing the whole dash out like the dealer charges you $1000+ to do. One thing going for '02 and later model owners is that Mits. starting putting a plastic wrap around the Powertrain Control Module (PCM) that is right under the heater core pipes, no doubt cause they knew had a leakage problem and didn't want to fix it right way.

One way to find out if there's still a leak is to clean up the carpet of all green residue and the smell as best you can (try baking soda). Pull the carpet up and away from the floor board and dry out the area underneath as well. Periodically check that area to see if any residue or moisture reappears. The leakage can be slow as to be hard to detect by inspecting the coolant overflow bottle level. Check above for link to the step by step procedure to do it, or I can repost on this website.

Hard to say if the light coming on is related, but you can go into any shop (may have to pay a diagnostic fee) or auto parts store (for free usually) to have them read the codes for you. That will at least tell you where the problem is.

I had a bad rear wheel ABS sensor that was turning my ABS/ TCL light on and off. Took a sensor off a late model Diamante in local junkyard and replaced it myself for $150. Dealer wanted $550 do do it. Right!

Once the two above biggest and potentially most expensive problems with this vehicle are fixed, it runs just fine. Good luck!

11th Jun 2009, 21:43

I also own a 2002 Diamante and just spent $1500 to have the heater core replaced and now my A/C does not work. The garage said it will be another $1300 to get a new evaporator core.

Did anyone look into any recalls on the heater or evaporator core? This is ridiculous that we are all having the same problems and Mitsubishi hasn't done anything about it.

22nd Jun 2009, 15:38

In order to repair/replace the heater core, you have to disconnect the A/C lines from the engine compartment to the evapaorator, evacuate the refrigerant, and remove the evaporator unit itself from under the dash. I know cause I did this repair myself on my 02 VR-X last year. I'd say there is a high likelihood that the shop that repaired your heater core may be responsible for you're a/C system not working, possible due to damage caused, misassembly, lack of adequate or leaking refrigerant during the heater core repair. I would go back to the shop that replace your heater core and asked them to explain this strange coincidence.

29th Jun 2009, 14:24

I have a similar problem with my Diamante 2002 model. Heater core leakage, Drive and Neutral lights flash, service engine light on. Dealer says min $3000 to fix. EBS is gone because the leakage.

6th Aug 2009, 10:30

Hi all.

Just like you, the transmission started acting funny for no reason. Took everything apart and there is significant evidence of coolant on the plastic that protects the ECM and the floorboard.

Everyone keeeps talking about a "transmission relay". Where is this?

I have a 2001 Diamante LS with 135K miles.

I found a local junkyard that has the ECM I have (w/traction).

I have 3 boxes in the front center of the car:

1. Air bag module (very bottom of ECM) part MR538276

2. ECM part MR514497

3. Traction control box (just below the radio mounted vertically) part MR502450.

Where is the mystery "transmission relay"?


17th Aug 2009, 20:05

The ECM (engine Control module) is also called the Powertrain Control Module (PCM). You found it apparently, under center of dash, forward of center console. In later Diamante models Mits. put plastic wrap over it to protect it from their own poor heater core gasket joint design. Very sad! The transmission control relay you asked about is also under the right side of the dash near center console. It has four wires coming out - black to ground, red/white to the PCM, orange to PCM, and white/black to the engine compartment fuse box (20A engine control fuse).

I too had coolant smell, wet carpet, in my 02 VRX with 85,000 miles. Found procedure on line and fixed it myself with $2.50 gaskets from dealer, with only partially removing dash under glove box, and not the whole dash as the dealer will charge you for. The coolant leaks right down on the PCM, which is directly under the heater core piping joint where it connects thru the firewall to the engine compartment coolant lines. Shame that a $1 poorly designed gasketed joint is the culprit for 100's of thousands of repair $$ and many unhappy customers.

Happy hunting!

Marco in Indy.