Thread: GTP engine temp/ac questions/problems

Aight. So its been hot the last two weeks in KC, like upper 90's. So the car is running hot--engine temp is getting over 3/4 on the dial, sometimes it gets up to the mark just before the red.

First, my car leaks no coolant. So, its full. Maybe it needs changed? Ok, but here's the deal. Last Saturday my wife was driving the car and it made two dinging sounds. Since that time, the DIC hasn't worked. So I checked the fuses. Fuses look good. Not too big of a deal that it went blank. BUT, what is a big deal is this is when the car started running hot. It hasn't over heated, though. So I thought maybe the cooling fans aren't kicking on. I have one of those ZZP PCM's that turns the fans on when you shut the car off.

I got to thinking about it and I hadn't heard them running when I shut the car off. So I open the fuse/relay box and flip those around to see if any other system malfunctions instead of the cooling fans. Although, there are three different relays for the cooling fans with one of them being different than the other two. There is a relay that is for the ignition that is the same as two of the cooling fans. So I flip them around. Car still starts and the fans seemingly work after that. So, I'm thinking, "I don't know that worked, but it did. Don't care now. Its working."

Well, today it starts running hot again after being fine the last few days. Another thing I've noticed is since my wife drove the car that day, the blower for the AC/Heater has quit working twice. Just quit. Turning the car off and back on and moving the dial back and forth apparantly got it to work again.

When the engine temp gets too high, the AC starts blowing hot air. I kind of expect the engine temp to climb a bit when the car is idling and it to drop back down to 210 or under when its moving. But it wasn't dropping even when I was moving....until I shut the AC off. Then it dropped back to 210. Turned the AC on, car temp climbs back up.

When I got home I thought I'd check the fans again. Well, one fan runs and the other doesn't. If you're facing the car, the one on the right works and the one of the left does nothing. So I flipped the two relays around that are the same hoping it would give me a different result, but nah. Same one kicked on and the other one stayed put.

I really don't know how these systems are related. Are the fans not working properly? What's up with DIC going blank? I'm sure the Tstat is opening. I felt the pressure of it opening on the upper radiator hose.

Is it just that hot outside and running the AC is just going to make it that much more difficult on the car (AC is charged, btw)? Is my coolant that bad? Its the green kind. After various repairs I've drained a good portion of it and refilled it so its not really old. The previous owner said she had it flushed not long before I bought it as well. And its not leaking.

Just waiting until Wednesday, I guess, when it is supposed to cool down in the 80's.

see if you can swap the fan wire plugs around, see if the left one will work then if not its the fan.

if the plugs dont match, try running 12 volts to the fan and a ground wires off the cars battery to see if it turns on.

i will try switching the plugs when my hands wont be melted off. stupid heat.

thanks ford man for the info on the AC fan. I did not know how those were set up. so if the ac is not on the left fan should never activate? and, if its not activating when the AC is on, this is what is causing the car to run so hot? is the coolant system somehow tied to the Air Conditioning system?

both my fans turn on when the ac is turned on and both stay on till i turn it off unless its hot enough temp wise for the fans to come on.

ive never seen only one fan turning ever on my car.

the next morning i attempted to flip the fan plugs around. that wasn't happening. the right fan plug is buried in a recessed area that seemed like could only be accessed from underneath. however, both fans worked first thing in the morning, car ran fine all day. upper 90's. no problems since.

wish i had an answer. this seems like its going to just be one of those silly things that each car seems to have. like its character or something.

if they worked after you unplugged it or fiddled with the wires maybe it was a dirty plug or bad wire.

its possible because i did unplug the fan that wasn't working and plug it back in.

i also had another thought and i don't know if it could be related, but the previous owner put LED lights inside of the headlights, like a cheap AUDI impersonation or something. The right head light LEDs quit working for a few days so I traced the wires and kind of tugged on them and they worked after that. i really have no idea what kind of mess they made with the wiring or where it actually goes or what it is hooked to. she also had LED lights in the interior that weren't working. i was able to get those to work and put them on a switch so they weren't always on. i never use them, i just wanted to see if i could get them to work properly.

another clue might be the DIC going out. i wonder if there is a fuse in the unit itself. the fuse in the glove box for it is fine. but it quit almost simultaneously with the car running hot. that happened once before but i just unhooked the battery and hooked it back up and it was fine after that.

maybe there is just some wack wiring going on with those headlights, or an exposed wire touching something somewhere causing all kinds of silliness.

dont thing headlights or the dic could affect the temp sensor or the fans. but id be checking over the wires under the hood real close. re do the connections, or remove them halos if your not into them.

These are the stock fan and A/C settings for a 99 GTP. I'd imagine your car would have very similar settings. Might help you troubleshoot.

Looks like your A/C should shut off when your coolant temp hits 255 degrees. That's pretty darn hot.

Good luck finding the issue.

i was just out in my car, when i turn my ac on at idle. the rpm's jump up like 200 rpm, then drop back to normal. does it one time.

maybe the cc vac box in the dash is bad? not sure. but if you cant find one of them vac lines under the hood busted id look there next.

This sounds about what was going on. when the engine temp got up to near the top of the dial, only hot air was coming out of the vents. this is just a maze of problems because according to the GM info you posted, fan number 2 did not turn on after 226F when the car was running hot. So I guess the second fan was not able to cool the coolant enough? or maybe the coolant sucks and needs flushed as well and that could be a contributing factor. That wouldn't affect the fan coming on or off, but it might still not get as hot if it were new and mixed properly. BUT, the next morning when the car was cool, and it was only 85 outside (Ha Ha) both fans turned on when i ran the AC first thing in the morning and it was fine all day--even up to the upper 90's. engine temp never went over 210.

it has a canned PCM from zzp. doesn't seem like they would mess with the fan settings while the car is running? they do kick on when you shut the car off, though.

Originally Posted by GTP131

These are the stock fan and A/C settings for a 99 GTP. I'd imagine your car would have very similar settings. Might help you troubleshoot.

Looks like your A/C should shut off when your coolant temp hits 255 degrees. That's pretty darn hot.

Good luck finding the issue.

Originally Posted by Scottydoggs

i was just out in my car, when i turn my ac on at idle. the rpm's jump up like 200 rpm, then drop back to normal. does it one time.

maybe the cc vac box in the dash is bad? not sure. but if you cant find one of them vac lines under the hood busted id look there next.

What is the cc vac box? I did replace every vacuum line I could see under the hood last year shortly after I bought it but I can check them again.

The halo lights are kinda cool, but kinda redneck so I don't know. haven't decided. i can't figure out how they hooked them up. they aren't tied into the stock wiring assembly at the headlights, I know that. They run on separate wiring but I haven't found where they go. They operate as the stock headlights operate. If the headlights are on, the Halos are on. If they are off, the halos are off. There are 3 different wires hooked to the post at the fuse/relay box under the hood. One is the sub, the other are the interior lights--maybe the other is the halo lights. there should be a stock wire hooked to it, too, though, I think. So maybe there are four. seems like they would need to be hooked up to something else as a remote though.

I don't seem to remember this stuff very well sitting at the computer and I don't pay close enough attention to remember when I'm looking under the hood

pass side, take the foot cover off, then take all the molding off at the door so the carpet can be pulled back. pull tthe carpet back so you can see the fire wall. just under the fan a box there you'll see a load of wires enter the car, one is the black hard vac line from under the fuse box.

follow this line it the console, theres a box back therethe line runs to, then 2 yellow lines leave it to the vac pumps in the dash that change the air flow.

does all that work? the def, floor, vent. like you can change it still? if not id think that box is suspect for sure. or the line running to it.

car running listen for a hiss under there, or a cracked line. work the controls while listening. you'll hear air when its changing air flow, but it stops.

OP, if it is a ZZP tune, you can throw the original fan settings I posted out the window. If I recall correctly, ZZP sets the fan on/off points to maintain around 185*. Are you using a 180* thermostat with this PCM tune? That may be a consideration.

Originally Posted by Scottydoggs

pass side, take the foot cover off, then take all the molding off at the door so the carpet can be pulled back. pull tthe carpet back so you can see the fire wall. just under the fan a box there you'll see a load of wires enter the car, one is the black hard vac line from under the fuse box.

follow this line it the console, theres a box back therethe line runs to, then 2 yellow lines leave it to the vac pumps in the dash that change the air flow.

does all that work? the def, floor, vent. like you can change it still? if not id think that box is suspect for sure. or the line running to it.

car running listen for a hiss under there, or a cracked line. work the controls while listening. you'll hear air when its changing air flow, but it stops.

all that stuff is working fine except the blower in the car for the AC/heater quit a couple times since I've had the problem. I forgot to mention that.

Originally Posted by GTP131

OP, if it is a ZZP tune, you can throw the original fan settings I posted out the window. If I recall correctly, ZZP sets the fan on/off points to maintain around 185*. Are you using a 180* thermostat with this PCM tune? That may be a consideration.

I do believe it has the 180 Tstat in it. I can't remember because i put it in when i got the pcm and it still ran at 195. and it was leaking so i just took it out and put the stock one back in. but i think i changed it back around hoping i just didn't seal the coolant line properly or put the gasket on wrong or something. regardless, whether it was the stock 195 or the 180 the engine temp was still 195 or higher. it actually goes up to 210 usually during the spring and summer.

thanks for your help guys. i do appreciate it. with every little thing that goes wrong that i post on here i learn more about vehicles in general like two fold somehow. there seems to always be a nugget discovered i never would have thought of. it really helps me when i'm helping other people with their cars around town and stuff. i pay it forward for sure.

Caught it in the act today. I drive all day for my job so I am frequently stopping and starting the car. Most of the day its fine, but on the way home car starts running hot. Pull in and check the fans. Right fan not working. Grab the plug and wiggle it and it kicks on. So it is a bad plug/wire/connection at the fan. It only happens when it is over 90 degrees outside. So I wonder if it being so hot under the hood is making the wires a little more pliable and they sag or something causing the bad connection. or it could just be coincidence.

get some electrical grease and some electrical parts cleaner, open the plug, spray the plug ends, then grease the falt side and plug it back in and work it in and out with the plug a few times.


also check the wires at the end of the plugs, they maybe cracked.