HELP!!! ABS Fuse, Tach and AC Problems

I need some major help. I have already had my 99 grand prix to 2 dealerships and after many hundreds of dollars have been told once again that they cannot help me. First, I have taken it in for the tach dropping. It has been put on the computer about 10 times and have been told there are no codes and there is not a problem. However, the tach will drop sometimes and occasionally will cause the car to jump or die. Lastly, the big problem is that the AC has been crazy. It first started that it would be on heat and you could not make it change to cold no matter what, it would even blow when it was turned off. Then after about 5-6 times starting the car it would stick on AC and it wouldn't turn to heat, no matter how many times you turned it on. Now my fuse has blown which has caused the ABS light to come on and no AC. The vent will blow but it has no AC and I still cannot turn it from heat to cold. I have spent just about everything. If I replace the fuse it blows within about 3 minutes. Anyone got any suggestions? This thing blowing heat on a 95 degree day is awful. Even with the fan turned off it still blows. I have replaced Ignition Switch Harness, Ignition Control Module, cam sensor, plugs, and wires. I just need some suggestions from anyone about something I haven't bought or tried. Thanks in advance. :banghead:

Needless to say when the ABS fuse pops you lose A/C since the fuse is shared. Since the fuse is popping the problem sounds like it is within the A/C or ABS circuits.

Questions:

Do you have manual HVAC or digital climate control?

With the ABS fuse blown does the engine still jump or die?

I noticed cam position sensor was changed but what about the crank position sensor? The tach dropping right befoe stall out is typically a crank position sensor problem due to flaky 18X timing pulses to the ICM module which also provides the tach signal. A dealer's Tech II may not properly diagnose a bad CKPS if no codes or SES light is triggered.

With ignition to off was the blower still operating? If so it sounds like a flaky blower motor resistor if manual or blower motor control module if digital climate control.

Sounds like you have more than one problem. Some appear to be associated but others do not and should be troubleshot individually based on the symptoms.

Also, it would be helpful to post your mileage, model Grand Prix and engine size.

Thank you so much for replying. I am so glad to get any suggestions. In answer to your first question, I have manual climate control. My blower does not operate while the ignition is off. You can turn the fan off and it is like it doesn't shut it really off, you can feel air flowing through it but not really a fan setting--it isn't forced air. It seems like when you manually turn the dial that it use to make a vaccuum sound when it changed from air-heat etc. Now I cannot get it to make that sound. It seems like something is really not shutting off or closing when it should. I do not even have a clue as to why it would be on heat and you turn the knob to cold and it still blows heat. The other question about the fuse being blown does it still die. The tach has been dropping and it has been dying for around 6 months, whereas this air problem has only happened it the past month. But even with the ABS fuse down it still stalls or dies. I have put in new fuses several times and it will last around 45 sec to 2 1/2 minutes. In your question about CKPS, I called the garage to find out exactly what they installed, they told me they installed a 7xCrank Sensor. Thank you so much for your reply. I am at wits end.

Thank you so much for replying. I am so glad to get any suggestions. In answer to your first question, I have manual climate control. My blower does not operate while the ignition is off. You can turn the fan off and it is like it doesn't shut it really off, you can feel air flowing through it but not really a fan setting--it isn't forced air. It seems like when you manually turn the dial that it use to make a vaccuum sound when it changed from air-heat etc. Now I cannot get it to make that sound. It seems like something is really not shutting off or closing when it should. I do not even have a clue as to why it would be on heat and you turn the knob to cold and it still blows heat. The other question about the fuse being blown does it still die. The tach has been dropping and it has been dying for around 6 months, whereas this air problem has only happened it the past month. But even with the ABS fuse down it still stalls or dies. I have put in new fuses several times and it will last around 45 sec to 2 1/2 minutes. In your question about CKPS, I called the garage to find out exactly what they installed, they told me they installed a 7xCrank Sensor. Thank you so much for your reply. I am at wits end.


I didn't see engine size so I am assuming it is a 3.1L since you mentioned 7X crank sensor. The wrong one may have been replaced. The main crank sensor (CKPS) is the 24X behind the harmonic balancer pulley. Based on the symptoms try replacing the 24X CKPS.

On the ABS/AC problem, you will need to isolate which circuit is causing the problem. Is it ABS or A/C? The fuse feeds the EBCM module for the ABS system and the A/C Compressor Clutch so it is 50/50.

To rule out A/C in which the fuse feeds the compressor clutch, pull the AC Clutch relay or the diode out and then see what it does. It is located in the engine compartment fuse box. If the fuse still pops then it may be the ABS braking system. Try that and we can go from there.

BTW - Also, get the ignition control module (ICM) tested.

Okay, I came home from work and tried the suggestions you made. My mother should not have sent me to cooking school considering I am spending more time under my car than at my stove. Okay, first of all you were right I do have a 3.1 engine. I will order the 24X CKPS and try it. It cannot hurt. Thanks for the suggestion. Okay on this awful AC problem. I took the diode out and put a new fuse in so that I would know if it blew. So it was running fine no blown fuse. Then I decided to try the AC and holy cow it ran without a diode. You can tell I don't know a thing about my car (it may suppose to do that) But anyway needless to say in 5 secs it blew. Had great AC for that time though. Should I have not tried the aC with the diode out to determine for ABS? If so, let me know and I will put in another fuse and not turn on AC without diode. It was doing fine with it out and hadn't blown so I thought I would turn it on and the ac compressor thingy( i think that is it) kicked in and started blowing cold air. Thanks so much for your patience with an absolute car idiot.

Also forgot to tell you that it is a 1999 Pontiac Grand Prix SE, 121,000 miles.

Okay, I came home from work and tried the suggestions you made. My mother should not have sent me to cooking school considering I am spending more time under my car than at my stove. Okay, first of all you were right I do have a 3.1 engine. I will order the 24X CKPS and try it. It cannot hurt. Thanks for the suggestion. Okay on this awful AC problem. I took the diode out and put a new fuse in so that I would know if it blew. So it was running fine no blown fuse. Then I decided to try the AC and holy cow it ran without a diode. You can tell I don't know a thing about my car (it may suppose to do that) But anyway needless to say in 5 secs it blew. Had great AC for that time though. Should I have not tried the aC with the diode out to determine for ABS? If so, let me know and I will put in another fuse and not turn on AC without diode. It was doing fine with it out and hadn't blown so I thought I would turn it on and the ac compressor thingy( i think that is it) kicked in and started blowing cold air. Thanks so much for your patience with an absolute car idiot.

Have you located the AC Clutch Relay in the engine compartment fuse box? Pull that and then put in a new ABS fuse and see what it does.

okay, i pulled the relay and the fuse didn't blow. so i assume that means that it is the AC causing the problem. i looked for any bad wires at fuse box but didn't see any so not really sure what is causing the AC to blow. Thanks as always

okay, i pulled the relay and the fuse didn't blow. so i assume that means that it is the AC causing the problem. i looked for any bad wires at fuse box but didn't see any so not really sure what is causing the AC to blow. Thanks as always

Not a problem and you are welcome. Ok, you can rule out ABS. ABS was acting up solely because of the fuse blowing.

That leaves the AC Clutch Relay or the A/C Compressor Clutch coil as the problem blowing the ABS/AC fuse.

Try disconnecting the wiring harness at the A/C compressor with the AC Clutch Relay installed and see what it does. You are down to 50/50 on the problem. Good luck!

BTW - Also, I would ohm out or do a check on the clutch coil diode just to be safe.

okay, i understood all of that except for the part about the A/C Compressor Clutch coil. where is that or can you give me a general idea where to find it?

okay, i understood all of that except for the part about the A/C Compressor Clutch coil. where is that or can you give me a general idea where to find it?

In front of the A/C compressor where you see the drive belt and pulley is the clutch.

Okay thanks found it with no trouble. I'm learning here. I pulled out the wiring harness and left the AC Clutch Relay installed and turned on the car etc and the new fuse didn't blow. I also checked the ohm's on the diode and it turned out fine. So I guess that means the relay is okay but haven't a clue where that leaves me. Thanks again so much for your help.

It looks like the A/C compressor clutch coil is bad. The AC Delco part number is 15-4439. It could be replaced DIY individually without having to replace the whole compressor. Or have a shop do it after getting some estimates.

The clutch will need to be disasembled to replace the coil. It is oval in design with the electrical connector. To get to it you'll need to remove the serpentine drive belt and the clutch pulley. It is located behind the pulley.

Good luck and let us know how it turns out.

BTW - The GM part number is 6552422, list price $87.20.

that still leaves you with the tach dropping problem... mine does that as well i have no clue whats causing it if anybody knows or you find out please enlighten me

oops my bad ^^disregard 24x sensor.. i have the 3.8 non sc engine tho

oops my bad ^^disregard 24x sensor.. i have the 3.8 non sc engine tho

You have a 18X crank position sensor and it is most likely the cause of your problem on a SII 3800. You'll never know until it is replaced. $25 part and about a 90 minute job.